Methods and Materials for Biosynthesis of Manoyl Oxide

This disclosure relates recombinant production of manoyl oxide in recombinant hosts. The disclosure also provides methods for producing terpenoids using manoyl oxide as a precursor or an intermediate.

Terpenoids are a diverse class of molecules with a wide variety of applications, including pharmaceuticals, cosmetics, food preparation, and fragrances. One such terpenoid, forskolin, is produced by Coleus forskohlii (C. forskohlii). Forskolin has been shown to decrease intraocular pressure and is used as an antiglaucoma agent (Wagh et al., 2012, J Postgrad Med. 58(3):199-202). Moreover, a water-soluble analogue of forskolin (NKH477) has been approved for commercial use in Japan for treatment of acute heart failure and heart surgery complications (Kikura et al., 2004, Pharmacol Res. 49(3):275-81). Forskolin also acts as bronchodilator (Yousif & Thulesius, 1999, J Pharm Pharmacol. 51(2):181-6) and may be used to treat obesity by contributing to higher rates of body fat burning and promoting lean body mass formation (Godard et al., Obes Res. 2005, 13(8):1335-43). Another terpenoid, ambrox, is a component of ambergris, a substance secreted from the intestines of the sperm whale, is useful in the perfume industry (Schalk et al., J Am Chem Soc. 134(46):18900-3).

The diterpene, manoyl oxide, is a precursor of forskolin and ambrox. Pateraki et al., 2014, Plant Physiol. 164(3):1222-6 showed that manoyl oxide localizes to oil bodies in C. forskohlii. Pateraki also demonstrated functional characterization of four CfTPSs from C. forskohlii. CfTPS2 was found to synthesize the intermediate copal-8-ol diphosphate, and in combination with CfTPS3 or CfTPS4 resulted in the stereospecific formation of (13R) manoyl oxide in planta.

As recovery and purification of forskolin and ambrox have proven to be labor intensive and inefficient (see, e.g., Nielsen et al., 2014, Appl Environ Microbiol. 80(23):7258-65, Harde & Singhal, 2012, Separation and Purification Technology 96:20-5 and Frija et al., 2011, 111(8):4418-52), there remains a need for a recombinant production system that can produce high yields of desired forskolin and ambrox, as well as their precursors, including manoyl oxide.

It is against the above background that the present invention provides certain advantages and advancements over the prior art.

Although this invention disclosed herein is not limited to specific advantages or functionalities, the invention provides a recombinant host comprising:

• • (a) a gene encoding a geranylgeranyl diphosphate synthase (GGPPS) polypeptide;
  • (b) a gene encoding a polypeptide capable of catalyzing formation of copal-8-ol diphosphate from geranylgeranyl diphosphate (GGPP); and
  • (c) a gene encoding a polypeptide capable of catalyzing formation of manoyl oxide from copal-8-ol diphosphate;
  • wherein at least one of the genes is a heterologous gene; and
  • wherein the recombinant host is capable of producing manoyl oxide.

In some aspects of the recombinant host disclosed herein, the GGPPS polypeptide comprises a GGPPS7 polypeptide having at least 70% identity to the amino acid sequence set forth in SEQ ID NO:2 or a GGPPS10 polypeptide having at least 70% identity to the amino acid sequence set forth in SEQ ID NO:2.

In some aspects of the recombinant host disclosed herein, the enzyme capable of catalyzing formation of copal-8-ol diphosphate from GGPP is a terpene synthase 2 (TPS2) polypeptide.

In some aspects of the recombinant host disclosed herein, the enzyme capable of catalyzing formation of manoyl oxide from copal-8-ol diphosphate is a terpene synthase 3 (TPS3) polypeptide or a terpene synthase 4 (TPS4) polypeptide.

In some aspects of the recombinant host disclosed herein, the TPS3 polypeptide comprises a TPS3 polypeptide having at least 70% identity to an amino acid sequence set forth in SEQ ID NO:9.

In some aspects of the recombinant host disclosed herein, the TPS4 polypeptide comprises a TPS4 polypeptide having at least 70% identity to an amino acid sequence set forth in SEQ ID NO:11.

In some aspects of the recombinant host disclosed herein, the recombinant host comprises a plant cell, a mammalian cell, an insect cell, a fungal cell, or a bacterial cell.

In some aspects of the recombinant host disclosed herein, the bacterial cell comprises Escherichia bacteria cells, Lactobacillus bacteria cells, Lactococcus bacteria cells, Cornebacterium bacteria cells, Acetobacter bacteria cells, Acinetobacter bacteria cells, or Pseudomonas bacterial cells.

In some aspects of the recombinant host disclosed herein, the fungal cell comprises a yeast cell.

In some aspects of the recombinant host disclosed herein, the yeast cell is a cell from Saccharomyces cerevisiae, Schizosaccharomyces pombe, Yarrowia lipolytica, Candida glabrata, Ashbya gossypii, Cyberlindnera jadinii, Pichia pastoris, Kluyveromyces lactis, Hansenula polymorpha, Candida boidinii, Arxula adeninivorans, Xanthophyllomyces dendrorhous, or Candida albicans species.

In some aspects of the recombinant host disclosed herein, the yeast cell is a Saccharomycete.

In some aspects of the recombinant host disclosed herein, the yeast cell is a cell from the Saccharomyces cerevisiae species.

The invention also provides a method of producing manoyl oxide, comprising:

• • (a) growing the recombinant host disclosed herein in a culture medium, under conditions in which any of the genes disclosed herein are expressed;
    • wherein the manoyl oxide is synthesized by said host; and/or
  • (b) optionally quantifying the manoyl oxide; and/or
  • (c) optionally isolating the manoyl oxide.

In some aspects of the method disclosed herein, the manoyl oxide is (13R) manoyl oxide.

The invention also provides a method for producing a terpenoid, comprising:

• • (a) growing the recombinant host disclosed herein in a culture medium, under conditions in which any of the genes disclosed herein are expressed;
    • wherein the manoyl oxide is synthesized by said host;
  • (b) isolating the manoyl oxide produced by said host; and/or
  • (c) converting the manoyl oxide into a terpenoid.

In some aspects of the method disclosed herein, the manoyl oxide is isolated from the microorganism and/or from the cultivation medium.

In some aspects of the method disclosed herein, the manoyl oxide is converted to the terpenoid by organic chemical synthesis.

In some aspects of the method disclosed herein, the terpenoid is forskolin.

In some aspects of the method disclosed herein, the terpenoid is ambrox.

These and other features and advantages of the present invention will be more fully understood from the following detailed description taken together with the accompanying claims. It is noted that the scope of the claims is defined by the recitations therein and not by the specific discussion of features and advantages set forth in the present description.

Before describing the present invention in detail, a number of terms will be defined. As used herein, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. For example, reference to a “nucleic acid” means one or more nucleic acids.

It is noted that terms like “preferably,” “commonly,” and “typically” are not utilized herein to limit the scope of the claimed invention or to imply that certain features are critical, essential, or even important to the structure or function of the claimed invention. Rather, these terms are merely intended to highlight alternative or additional features that can or cannot be utilized in a particular embodiment of the present invention.

For the purposes of describing and defining the present invention it is noted that the term “substantially” is utilized herein to represent the inherent degree of uncertainty that can be attributed to any quantitative comparison, value, measurement, or other representation. The term “substantially” is also utilized herein to represent the degree by which a quantitative representation can vary from a stated reference without resulting in a change in the basic function of the subject matter at issue.

Methods well known to those skilled in the art can be used to construct genetic expression constructs and recombinant cells according to this invention. These methods include in vitro recombinant DNA techniques, synthetic techniques, in vivo recombination techniques, and polymerase chain reaction (PCR) techniques. See, for example, techniques as described in Green & Sambrook, 2012, MOLECULAR CLONING: A LABORATORY MANUAL, Fourth Edition, Cold Spring Harbor Laboratory, New York; Ausubel et al., 1989, CURRENT PROTOCOLS IN MOLECULAR BIOLOGY, Greene Publishing Associates and Wiley Interscience, New York, and PCR Protocols: A Guide to Methods and Applications (Innis et al., 1990, Academic Press, San Diego, Calif.).

As used herein, the terms “polynucleotide,” “nucleotide,” “oligonucleotide,” and “nucleic acid” can be used interchangeably to refer to nucleic acid comprising DNA, RNA, derivatives thereof, or combinations thereof.

As used herein, the terms “microorganism,” “microorganism host,” “microorganism host cell,” “recombinant host,” and “recombinant host cell” can be used interchangeably. As used herein, the term “recombinant host” is intended to refer to a host, the genome of which has been augmented by at least one DNA sequence. Such DNA sequences include but are not limited to genes that are not naturally present, DNA sequences that are not normally transcribed into RNA or translated into a protein (“expressed”), and other genes or DNA sequences which one desires to introduce into a host. It will be appreciated that typically the genome of a recombinant host described herein is augmented through stable introduction of one or more recombinant genes. Generally, introduced DNA is not originally resident in the host that is the recipient of the DNA, but it is within the scope of this disclosure to isolate a DNA segment from a given host, and to subsequently introduce one or more additional copies of that DNA into the same host, e.g., to enhance production of the product of a gene or alter the expression pattern of a gene. In some instances, the introduced DNA will modify or even replace an endogenous gene or DNA sequence by, e.g., homologous recombination or site-directed mutagenesis. Suitable recombinant hosts include microorganisms.

As used herein, the term “recombinant gene” refers to a gene or DNA sequence that is introduced into a recipient host, regardless of whether the same or a similar gene or DNA sequence may already be present in such a host. “Introduced,” or “augmented” in this context, is known in the art to mean introduced or augmented by the hand of man. Thus, a recombinant gene can be a DNA sequence from another species or can be a DNA sequence that originated from or is present in the same species but has been incorporated into a host by recombinant methods to form a recombinant host. It will be appreciated that a recombinant gene that is introduced into a host can be identical to a DNA sequence that is normally present in the host being transformed, and is introduced to provide one or more additional copies of the DNA to thereby permit overexpression or modified expression of the gene product of that DNA. In some aspects, said recombinant genes are encoded by cDNA. In other embodiments, recombinant genes are synthetic and/or codon-optimized for expression in S. cerevisiae.

As used herein, the term “engineered biosynthetic pathway” refers to a biosynthetic pathway that occurs in a recombinant host, as described herein. In some aspects, one or more steps of the biosynthetic pathway do not naturally occur in an unmodified host. In some embodiments, a heterologous version of a gene is introduced into a host that comprises an endogenous version of the gene.

As used herein, the term “endogenous” gene refers to a gene that originates from and is produced or synthesized within a particular organism, tissue, or cell. In some embodiments, the endogenous gene is a yeast gene. In some embodiments, the gene is endogenous to S. cerevisiae, including, but not limited to S. cerevisiae strains. In some embodiments, an endogenous yeast gene is overexpressed. As used herein, the term “overexpress” is used to refer to the expression of a gene in an organism at levels higher than the level of gene expression in a wild type organism. See, e.g., Prelich, 2012, Genetics 190:841-54. In some embodiments, an endogenous yeast gene is deleted. See, e.g., Giaever & Nislow, 2014, Genetics 197(2):451-65. As used herein, the terms “deletion,” “deleted,” “knockout,” and “knocked out” can be used interchangeably to refer to an endogenous gene that has been manipulated to no longer be expressed in an organism, including, but not limited to, S. cerevisiae.

As used herein, the terms “heterologous sequence” and “heterologous coding sequence” are used to describe a sequence derived from a species other than the recombinant host. In some embodiments, the recombinant host is an S. cerevisiae cell, and a heterologous sequence is derived from an organism other than S. cerevisiae. A heterologous coding sequence, for example, can be from a prokaryotic microorganism, a eukaryotic microorganism, a plant, an animal, an insect, or a fungus different than the recombinant host expressing the heterologous sequence. In some embodiments, a coding sequence is a sequence that is native to the host.

A “selectable marker” can be one of any number of genes that complement host cell auxotrophy, provide antibiotic resistance, or result in a color change. Linearized DNA fragments of the gene replacement vector then are introduced into the cells using methods well known in the art (see below). Integration of the linear fragments into the genome and the disruption of the gene can be determined based on the selection marker and can be verified by, for example, PCR or Southern blot analysis. Subsequent to its use in selection, a selectable marker can be removed from the genome of the host cell by, e.g., Cre-LoxP systems (see, e.g., Gossen et al., 2002, Ann. Rev. Genetics 36:153-173 and U.S. 2006/0014264). Alternatively, a gene replacement vector can be constructed in such a way as to include a portion of the gene to be disrupted, where the portion is devoid of any endogenous gene promoter sequence and encodes none, or an inactive fragment of, the coding sequence of the gene.

As used herein, the terms “variant” and “mutant” are used to describe a protein sequence that has been modified at one or more amino acids, compared to the wild-type sequence of a particular protein.

The structures of manoyl oxide and (13R) manoyl oxide (13R-MO) are shown in FIG. 1. As used herein, the term “terpenoid” refers any terpenoid that can be produced using manoyl oxide as a precursor or an intermediate during synthesis. In some embodiments, the terpenoid is a diterpenoid. Non-limiting examples of terpenoids include forskolin and ambrox, the structures of which are also shown in FIG. 1. As described herein, manoyl oxide can be produced in vivo, in vitro, or by bioconversion.

As used herein, the term “substituted manoyl oxide” refers to a manoyl oxide molecule, wherein one or more hydrogens have been substituted with another moiety, also referred to as a “substituent.” Non-limiting examples of substituents include hydroxyl, oxo, carboxyl, carbonyl, or acyl groups. In some embodiments, the substituted manoyl oxide is forskolin.

In some embodiments, manoyl oxide is produced in vivo through expression of one or more enzymes involved in the manoyl oxide biosynthetic pathway in a recombinant host. For example, a geranylgeranyl diphosphate (GGPP)-producing recombinant host expressing a gene encoding a polypeptide capable of catalyzing conversion of GGPP to copal-8-ol diphosphate and a gene encoding a polypeptide capable of catalyzing conversion of copal-8-ol diphosphate to manoyl oxide can produce manoyl oxide in vivo.

In some embodiments, a host comprises i) a heterologous nucleic acid encoding a geranylgeranyl diphosphate synthase (GGPPS), ii) a heterologous nucleic acid encoding an enzyme capable of catalyzing formation of copal-8-ol diphosphate from geranylgeranyl diphosphate (GGPP), and iii) a heterologous nucleic acid encoding an enzyme capable of catalyzing formation of manoyl oxide from copal-8-ol diphosphate.

The GGPPS is capable of catalyzing conversion of farnesyl diphosphate (FPP) and isopentenyl diphosphate (IPP) to GGPP. In particular, the GGPPS can be any enzyme classified under EC 2.5.1.29. A host may comprise an endogenous GGPPS. In some embodiments, a manoyl oxide-producing host comprising a heterologous GGPPS produces higher amounts of manoyl oxide than a manoyl oxide-producing host comprising an endogenous GGPPS.

In some embodiments, the GGPPS is derived from Synechococcus sp., such as GGPPS7 of SEQ ID NO:2 or a GGPPS having at least 70% identity to SEQ ID NO:2. The GGPPS7 having an amino acid sequence set forth in SEQ ID NO:2 can be encoded by a nucleotide sequence set forth in SEQ ID NO:1. In other embodiments, the GGPPS is derived from Aspergillus nidulans, such as GGPPS10 of SEQ ID NO:4 or a GGPPS having at least 70% identity to SEQ ID NO:4. The GGPPS10 having an amino acid sequence set forth in SEQ ID NO:4 can be encoded by a nucleotide sequence set forth in SEQ ID NO:3. In some embodiments, a GGPPS polypeptide is encoded by a nucleotide sequence having at least 70% identity to SEQ ID NO:1 or SEQ ID NO:3.

In some embodiments, the enzyme capable of catalyzing formation of copal-8-ol diphosphate from GGPP comprises a terpene synthase 2 (TPS2) enzyme. The reaction catalysed by TPS2 is shown in FIG. 2A. In some embodiments, the TPS2 is TPS2 from C. forskohlii. In particular, the TPS2 can be the TPS2 of SEQ ID NO:6 or a TPS2 having at least 70% identity to SEQ ID NO:6. The TPS2 having an amino acid sequence set forth in SEQ ID NO:6 can be encoded by a nucleotide sequence set forth in SEQ ID NO:5 or SEQ ID NO:7. In some embodiments, a TPS2 polypeptide is encoded by a nucleotide sequence having at least 70% identity to SEQ ID NO:5 or SEQ ID NO:7.

In some embodiments, the enzyme capable of catalyzing formation of manoyl oxide from copal-8-ol diphosphate comprises a terpene synthase 3 (TPS3) or terpene synthase 4 (TPS4) enzymes. The reaction catalyzed by TPS3 or TPS4 is shown in FIG. 2B. In some embodiments, the TPS3 is a TPS3 from C. forskohlii. In particular, the TPS3 can be a TPS3 of SEQ ID NO:9 or a TPS3 having at least 70% identity to SEQ ID NO:9. The TPS3 having an amino acid sequence set forth in SEQ ID NO:9 can be encoded by a nucleotide sequence set forth in SEQ ID NO:8 or SEQ ID NO:10. In some embodiments, a TPS3 polypeptide is encoded by a nucleotide sequence having at least 70% identity to SEQ ID NO:8 or SEQ ID NO:10.

In some embodiments, the TPS4 is a TPS4 from C. forskohlii. In particular, the TPS4 can be a TPS4 of SEQ ID NO:11 or a TPS4 having at least 70% identity to SEQ ID NO:11. The TPS4 having an amino acid sequence can be encoded by a nucleotide sequence set forth in SEQ ID NO:12. In some embodiments, a TPS4 polypeptide is encoded by a nucleotide sequence having at least 70% identity to SEQ ID NO:12.

The recombinant hosts described herein are particularly useful for producing manoyl oxide. In some embodiments, the recombinant microorganisms according to the invention are capable of producing at least 2×, preferably at least 10×, more preferably at least 20×, such as at least 50×, for example at least 100× more manoyl oxide, compared to a manoyl oxide-producing organism that does not comprises a heterologous GGPPS, a heterologous TPS2, and/or a heterologous TPS3 or TPS4.

In some embodiments, the recombinant host described herein is capable of producing at least 3 g/L, such as at least 5 g/L, for example at least 7 g/L manoyl oxide after cultivation for approximately 120 h.

In some embodiments, a recombinant host described herein can further comprise i) a heterologous nucleic acid encoding enzymes involved in the biosynthesis of GGPP and/or of farnesyl diphosphate (FPP) and/or ii) a heterologous nucleic acid encoding enzymes involved in the biosynthesis of terpenoids. In some embodiments, a recombinant host is modified to reduce the activity of reactions consuming GGPP for other purposes. Thus, the recombinant host may further contain a construct to silence the expression of non-manoyl oxide pathways consuming GGPP or FPP, thereby providing increased flux towards manoyl oxide or manoyl oxide-derived products. For example, flux to sterol production pathways such as ergosterol may be reduced by downregulation of the ERG9 gene. In a non-limiting example, the native promoter of the ERG9 gene can be substituted for a weaker promoter, which results in lowered expression of ERG9. See, e.g., Asadollahi et al., 2010, Biotechnol Bioeng. 106(1):86-96 and Kennedy & Bard, 2001, Biochim Biophys Acta. 1517(2):177-89.

In another embodiment, a recombinant host described herein can comprise one or more genes encoding one or more enzymes in the MEP pathway or the mevalonate pathway. Such genes can increase the flux of carbon into the diterpene biosynthesis pathway, producing GGPP from IPP and dimethylallyl diphosphate (DMAPP) generated by the pathway.

In addition, expression of a truncated form of the enzyme 3-hydroxy-3-methylglutaryl-CoA reductase (tHMG1) can also increase levels of GGPP. A useful truncated form of yeast HMG reductase (tHMG1) is described in Donald et al., 1997, Appl. Environ. Microbiol. 63, 3341-3344.

In some embodiments, manoyl oxide is produced through contact of a manoyl oxide precursor with one or more enzymes involved in the manoyl oxide pathway in vitro. For example, contacting copal-8-ol diphosphate with a TPS3 or TPS4 polypeptide can result in production of a manoyl oxide in vitro.

In some embodiments, manoyl oxide is produced by whole cell bioconversion. For whole cell bioconversion to occur, a host cell expressing one or more enzymes involved in the manoyl oxide pathway takes up and modifies a manoyl oxide precursor in the cell; following modification in vivo, manoyl oxide remains in the cell and/or is excreted into the culture medium. For example, a host cell expressing a gene encoding a TPS3 or TPS4 polypeptide can take up copal-8-ol diphosphate and modify copal-8-ol diphosphate in the cell; following modification in vivo, manoyl oxide can be excreted into the culture medium. In some embodiments, the cell is permeabilized to take up a substrate to be modified or to excrete a modified product.

In some aspects, manoyl oxide produced herein can be converted to ambrox using a method described by Cambie et al., 1971, Australian Journal of Chemistry 24(3):583-91. In other aspects, manoyl oxide produced herein can be converted to forskolin. See, e.g., Nielsen et al., 2014, Appl Environ Microbiol. 80(23):7258-65 and Pateraki et al., 2014, Plant Physiol. 164(3):1222-6.

Functional homologs of the polypeptides described above are also suitable for use in producing manoyl oxide in a recombinant host. A functional homolog is a polypeptide that has sequence similarity to a reference polypeptide, and that carries out one or more of the biochemical or physiological function(s) of the reference polypeptide. A functional homolog and the reference polypeptide can be a natural occurring polypeptide, and the sequence similarity can be due to convergent or divergent evolutionary events. As such, functional homologs are sometimes designated in the literature as homologs, or orthologs, or paralogs. Variants of a naturally occurring functional homolog, such as polypeptides encoded by mutants of a wild type coding sequence, can themselves be functional homologs. Functional homologs can also be created via site-directed mutagenesis of the coding sequence for a polypeptide, or by combining domains from the coding sequences for different naturally-occurring polypeptides (“domain swapping”). Techniques for modifying genes encoding functional polypeptides described herein are known and include, inter alia, directed evolution techniques, site-directed mutagenesis techniques and random mutagenesis techniques, and can be useful to increase specific activity of a polypeptide, alter substrate specificity, alter expression levels, alter subcellular location, or modify polypeptide-polypeptide interactions in a desired manner. Such modified polypeptides are considered functional homologs. The term “functional homolog” is sometimes applied to the nucleic acid that encodes a functionally homologous polypeptide.

Functional homologs can be identified by analysis of nucleotide and polypeptide sequence alignments. For example, performing a query on a database of nucleotide or polypeptide sequences can identify homologs of manoyl oxide biosynthesis polypeptides. Sequence analysis can involve BLAST, Reciprocal BLAST, or PSI-BLAST analysis of non-redundant databases using a GGPPS, TPS2, TPS3, or TPS4 amino acid sequence as the reference sequence. Amino acid sequence is, in some instances, deduced from the nucleotide sequence. Those polypeptides in the database that have greater than 40% sequence identity are candidates for further evaluation for suitability as a manoyl oxide biosynthesis polypeptide. Amino acid sequence similarity allows for conservative amino acid substitutions, such as substitution of one hydrophobic residue for another or substitution of one polar residue for another. If desired, manual inspection of such candidates can be carried out in order to narrow the number of candidates to be further evaluated. Manual inspection can be performed by selecting those candidates that appear to have domains present in manoyl oxide biosynthesis polypeptides, e.g., conserved functional domains. In some embodiments, nucleic acids and polypeptides are identified from transcriptome data based on expression levels rather than by using BLAST analysis.

Conserved regions can be identified by locating a region within the primary amino acid sequence of a manoyl oxide biosynthesis polypeptide that is a repeated sequence, forms some secondary structure (e.g., helices and beta sheets), establishes positively or negatively charged domains, or represents a protein motif or domain. See, e.g., the Pfam web site describing consensus sequences for a variety of protein motifs and domains on the World Wide Web at sanger.ac.uk/Software/Pfam/ and pfam.janelia.org/. The information included at the Pfam database is described in Sonnhammer et al., Nucl. Acids Res., 26:320-322 (1998); Sonnhammer et al., Proteins, 28:405-420 (1997); and Bateman et al., Nucl. Acids Res., 27:260-262 (1999). Conserved regions also can be determined by aligning sequences of the same or related polypeptides from closely related species. Closely related species preferably are from the same family. In some embodiments, alignment of sequences from two different species is adequate to identify such homologs.

Typically, polypeptides that exhibit at least about 40% amino acid sequence identity are useful to identify conserved regions. Conserved regions of related polypeptides exhibit at least 45% amino acid sequence identity (e.g., at least 50%, at least 60%, at least 70%, at least 80%, or at least 90% amino acid sequence identity). In some embodiments, a conserved region exhibits at least 92%, 94%, 96%, 98%, or 99% amino acid sequence identity.

For example, polypeptides suitable for producing manoyl oxide in a recombinant host include functional homologs of GGPPS, TPS2, TPS3, or TPS4. Methods to modify the substrate specificity of, for example, GGPPS, TPS2, TPS3, or TPS4, are known to those skilled in the art, and include without limitation site-directed/rational mutagenesis approaches, random directed evolution approaches and combinations in which random mutagenesis/saturation techniques are performed near the active site of the enzyme. For example see Osmani et al., 2009, Phytochemistry 70: 325-347.

A candidate sequence typically has a length that is from 80% to 200% of the length of the reference sequence, e.g., 82, 85, 87, 89, 90, 93, 95, 97, 99, 100, 105, 110, 115, 120, 130, 140, 150, 160, 170, 180, 190, or 200% of the length of the reference sequence. A functional homolog polypeptide typically has a length that is from 95% to 105% of the length of the reference sequence, e.g., 90, 93, 95, 97, 99, 100, 105, 110, 115, or 120% of the length of the reference sequence, or any range between. A % identity for any candidate nucleic acid or polypeptide relative to a reference nucleic acid or polypeptide can be determined as follows. A reference sequence (e.g., a nucleic acid sequence or an amino acid sequence described herein) is aligned to one or more candidate sequences using the computer program ClustalW (version 1.83, default parameters), which allows alignments of nucleic acid or polypeptide sequences to be carried out across their entire length (global alignment). Chenna et al., 2003, Nucleic Acids Res. 31(13):3497-500.

ClustalW calculates the best match between a reference and one or more candidate sequences, and aligns them so that identities, similarities and differences can be determined. Gaps of one or more residues can be inserted into a reference sequence, a candidate sequence, or both, to maximize sequence alignments. For fast pairwise alignment of nucleic acid sequences, the following default parameters are used: word size: 2; window size: 4; scoring method: % age; number of top diagonals: 4; and gap penalty: 5. For multiple alignment of nucleic acid sequences, the following parameters are used: gap opening penalty: 10.0; gap extension penalty: 5.0; and weight transitions: yes. For fast pairwise alignment of protein sequences, the following parameters are used: word size: 1; window size: 5; scoring method: % age; number of top diagonals: 5; gap penalty: 3. For multiple alignment of protein sequences, the following parameters are used: weight matrix: blosum; gap opening penalty: 10.0; gap extension penalty: 0.05; hydrophilic gaps: on; hydrophilic residues: Gly, Pro, Ser, Asn, Asp, Gln, Glu, Arg, and Lys; residue-specific gap penalties: on. The ClustalW output is a sequence alignment that reflects the relationship between sequences. ClustalW can be run, for example, at the Baylor College of Medicine Search Launcher site on the World Wide Web (searchlauncher.bcm.tmc.edu/multi-align/multi-align.html) and at the European Bioinformatics Institute site on the World Wide Web (ebi.ac.uk/clustalw).

To determine % identity of a candidate nucleic acid or amino acid sequence to a reference sequence, the sequences are aligned using ClustalW, the number of identical matches in the alignment is divided by the length of the reference sequence, and the result is multiplied by 100. It is noted that the % identity value can be rounded to the nearest tenth. For example, 78.11, 78.12, 78.13, and 78.14 are rounded down to 78.1, while 78.15, 78.16, 78.17, 78.18, and 78.19 are rounded up to 78.2.

It will be appreciated that functional GGPPS, TPS2, TPS3, or TPS4 proteins can include additional amino acids that are not involved in the enzymatic activities carried out by the enzymes. In some embodiments, GGPPS, TPS2, TPS3, or TPS4 are fusion proteins. The terms “chimera,” “fusion polypeptide,” “fusion protein,” “fusion enzyme,” “fusion construct,” “chimeric protein,” “chimeric polypeptide,” “chimeric construct,” and “chimeric enzyme” can be used interchangeably herein to refer to proteins engineered through the joining of two or more genes that code for different proteins. In some embodiments, a nucleic acid sequence encoding a GGPPS, TPS2, TPS3, or TPS4 polypeptide can include a tag sequence that encodes a “tag” designed to facilitate subsequent manipulation (e.g., to facilitate purification or detection), secretion, or localization of the encoded polypeptide. Tag sequences can be inserted in the nucleic acid sequence encoding the polypeptide such that the encoded tag is located at either the carboxyl or amino terminus of the polypeptide. Non-limiting examples of encoded tags include green fluorescent protein (GFP), human influenza hemagglutinin (HA), glutathione S transferase (GST), polyhistidine-tag (HIS tag), and FIag™ tag (Kodak, New Haven, Conn.). Other examples of tags include a chloroplast transit peptide, a mitochondrial transit peptide, an amyloplast peptide, signal peptide, or a secretion tag.

In some embodiments, a fusion protein is a protein altered by domain swapping. As used herein, the term “domain swapping” is used to describe the process of replacing a domain of a first protein with a domain of a second protein. In some embodiments, the domain of the first protein and the domain of the second protein are functionally identical or functionally similar. In some embodiments, the structure and/or sequence of the domain of the second protein differs from the structure and/or sequence of the domain of the first protein. In some embodiments, a GGPPS, TPS2, TPS3, or TPS4 polypeptide is altered by domain swapping.

A recombinant gene encoding a polypeptide described herein comprises the coding sequence for that polypeptide, operably linked in sense orientation to one or more regulatory regions suitable for expressing the polypeptide. Because many microorganisms are capable of expressing multiple gene products from a polycistronic mRNA, multiple polypeptides can be expressed under the control of a single regulatory region for those microorganisms, if desired. A coding sequence and a regulatory region are considered to be operably linked when the regulatory region and coding sequence are positioned so that the regulatory region is effective for regulating transcription or translation of the sequence. Typically, the translation initiation site of the translational reading frame of the coding sequence is positioned between one and about fifty nucleotides downstream of the regulatory region for a monocistronic gene.

In many cases, the coding sequence for a polypeptide described herein is identified in a species other than the recombinant host, i.e., is a heterologous nucleic acid. Thus, if the recombinant host is a microorganism, the coding sequence can be from other prokaryotic or eukaryotic microorganisms, from plants or from animals. In some case, however, the coding sequence is a sequence that is native to the host and is being reintroduced into that organism. A native sequence can often be distinguished from the naturally occurring sequence by the presence of non-natural sequences linked to the exogenous nucleic acid, e.g., non-native regulatory sequences flanking a native sequence in a recombinant nucleic acid construct. In addition, stably transformed exogenous nucleic acids typically are integrated at positions other than the position where the native sequence is found. “Regulatory region” refers to a nucleic acid having nucleotide sequences that influence transcription or translation initiation and rate, and stability and/or mobility of a transcription or translation product. Regulatory regions include, without limitation, promoter sequences, enhancer sequences, response elements, protein recognition sites, inducible elements, protein binding sequences, 5′ and 3′ untranslated regions (UTRs), transcriptional start sites, termination sequences, polyadenylation sequences, introns, and combinations thereof. A regulatory region typically comprises at least a core (basal) promoter. A regulatory region also may include at least one control element, such as an enhancer sequence, an upstream element or an upstream activation region (UAR). A regulatory region is operably linked to a coding sequence by positioning the regulatory region and the coding sequence so that the regulatory region is effective for regulating transcription or translation of the sequence. For example, to operably link a coding sequence and a promoter sequence, the translation initiation site of the translational reading frame of the coding sequence is typically positioned between one and about fifty nucleotides downstream of the promoter. A regulatory region can, however, be positioned as much as about 5,000 nucleotides upstream of the translation initiation site, or about 2,000 nucleotides upstream of the transcription start site.

The choice of regulatory regions to be included depends upon several factors, including, but not limited to, efficiency, selectability, inducibility, desired expression level, and preferential expression during certain culture stages. It is a routine matter for one of skill in the art to modulate the expression of a coding sequence by appropriately selecting and positioning regulatory regions relative to the coding sequence. It will be understood that more than one regulatory region may be present, e.g., introns, enhancers, upstream activation regions, transcription terminators, and inducible elements.

One or more genes can be combined in a recombinant nucleic acid construct in “modules” useful for a discrete aspect of manoyl oxide production. Combining a plurality of genes in a module, particularly a polycistronic module, facilitates the use of the module in a variety of species. For example, a manoyl oxide biosynthesis gene cluster can be combined in a polycistronic module such that, after insertion of a suitable regulatory region, the module can be introduced into a wide variety of species. As another example, a manoyl oxide biosynthesis gene cluster can be combined such that each manoyl oxide pathway coding sequence is operably linked to a separate regulatory region, to form a manoyl oxide pathway module. Such a module can be used in those species for which monocistronic expression is necessary or desirable. In addition to genes useful for manoyl oxide production, a recombinant construct typically also contains an origin of replication, and one or more selectable markers for maintenance of the construct in appropriate species.

It will be appreciated that because of the degeneracy of the genetic code, a number of nucleic acids can encode a particular polypeptide; i.e., for many amino acids, there is more than one nucleotide triplet that serves as the codon for the amino acid. Thus, codons in the coding sequence for a given polypeptide can be modified such that optimal expression in a particular host is obtained, using appropriate codon bias tables for that host (e.g., microorganism). As isolated nucleic acids, these modified sequences can exist as purified molecules and can be incorporated into a vector or a virus for use in constructing modules for recombinant nucleic acid constructs.

Recombinant hosts can be used to express polypeptides for the producing manoyl oxide, including mammalian, insect, plant, and algal cells. A number of prokaryotes and eukaryotes are also suitable for use in constructing the recombinant microorganisms described herein, e.g., gram-negative bacteria, yeast, and fungi. A species and strain selected for use as a manoyl oxide production strain is first analyzed to determine which production genes are endogenous to the strain and which genes are not present. Genes for which an endogenous counterpart is not present in the strain are advantageously assembled in one or more recombinant constructs, which are then transformed into the strain in order to supply the missing function(s).

Typically, the recombinant microorganism is grown in a fermenter at a defined temperature(s) for a desired period of time. The constructed and genetically engineered microorganisms provided by the invention can be cultivated using conventional fermentation processes, including, inter alia, chemostat, batch, fed-batch cultivations, semi-continuous fermentations such as draw and fill, continuous perfusion fermentation, and continuous perfusion cell culture. Depending on the particular microorganism used in the method, other recombinant genes such as isopentenyl biosynthesis genes and terpene synthase and cyclase genes may also be present and expressed. Levels of substrates and intermediates, e.g., isopentenyl diphosphate, dimethylallyl diphosphate, GGPP, ent-kaurene and ent-kaurenoic acid, can be determined by extracting samples from culture media for analysis according to published methods.

Carbon sources of use in the instant method include any molecule that can be metabolized by the recombinant host cell to facilitate growth and/or production of the manoyl oxide. Examples of suitable carbon sources include, but are not limited to, sucrose (e.g., as found in molasses), fructose, xylose, ethanol, glycerol, glucose, cellulose, starch, cellobiose or other glucose-comprising polymer. In embodiments employing yeast as a host, for example, carbons sources such as sucrose, fructose, xylose, ethanol, glycerol, and glucose are suitable. The carbon source can be provided to the host organism throughout the cultivation period or alternatively, the organism can be grown for a period of time in the presence of another energy source, e.g., protein, and then provided with a source of carbon only during the fed-batch phase.

After the recombinant microorganism has been grown in culture for the desired period of time, manoyl oxide can then be recovered from the culture using various techniques known in the art. In some embodiments, a permeabilizing agent can be added to aid the feedstock entering into the host and product getting out. For example, a crude lysate of the cultured microorganism can be centrifuged to obtain a supernatant. The resulting supernatant can then be applied to a chromatography column, e.g., a C-18 column, and washed with water to remove hydrophilic compounds, followed by elution of the compound(s) of interest with a solvent such as methanol. The compound(s) can then be further purified by preparative HPLC. See also, WO 2009/140394.

It will be appreciated that the various genes and modules discussed herein can be present in two or more recombinant hosts rather than a single host. When a plurality of recombinant hosts is used, they can be grown in a mixed culture to accumulate manoyl oxide.

Alternatively, the two or more hosts each can be grown in a separate culture medium and the product of the first culture medium, e.g., copal-8-ol diphosphate, can be introduced into second culture medium to be converted into manoyl oxide. In another example, the product of the first culture medium, e.g., manoyl oxide, can be introduced into second culture medium to be converted into a subsequent intermediate, or into an end product such as, for example, forskolin or ambrox. The product produced by the second, or final host is then recovered. It will also be appreciated that in some embodiments, a recombinant host is grown using nutrient sources other than a culture medium and utilizing a system other than a fermenter.

Exemplary prokaryotic and eukaryotic species are described in more detail below. However, it will be appreciated that other species can be suitable. For example, suitable species can be in a genus such as Agaricus, Aspergillus, Bacillus, Candida, Corynebacterium, Eremothecium, Escherichia, Fusarium/Gibberella, Kluyveromyces, Laetiporus, Lentinus, Phaffia, Phanerochaete, Pichia, Physcomitrella, Rhodoturula, Saccharomyces, Schizosaccharomyces, Sphaceloma, Xanthophyllomyces or Yarrowia. Exemplary species from such genera include Lentinus tigrinus, Laetiporus sulphureus, Phanerochaete chrysosporium, Pichia pastoris, Cyberlindnera jadinii, Physcomitrella patens, Rhodoturula glutinis, Rhodoturula mucilaginosa, Phaffia rhodozyma, Xanthophyllomyces dendrorhous, Fusarium fujikuroi/Gibberella fujikuroi, Candida utilis, Candida glabrata, Candida albicans, and Yarrowia lipolytica.

In some embodiments, a microorganism can be a prokaryote such as Escherichia bacteria cells, for example, Escherichia coli cells; Lactobacillus bacteria cells; Lactococcus bacteria cells; Cornebacterium bacteria cells; Acetobacter bacteria cells; Acinetobacter bacteria cells; or Pseudomonas bacterial cells.

In some embodiments, a microorganism can be an Ascomycete such as Gibberella fujikuroi, Kluyveromyces lactis, Schizosaccharomyces pombe, Aspergillus niger, Yarrowia lipolytica, Ashbya gossypii, or S. cerevisiae.

In some embodiments, a microorganism can be an algal cell such as Blakeslea trispora, Dunaliella salina, Haematococcus pluvialis, Chlorella sp., Undaria pinnatifida, Sargassum, Laminaria japonica, Scenedesmus almeriensis species.

In some embodiments, a microorganism can be a cyanobacterial cell such as Blakeslea trispora, Dunaliella salina, Haematococcus pluvialis, Chlorella sp., Undaria pinnatifida, Sargassum, Laminaria japonica, Scenedesmus almeriensis.

Saccharomyces is a widely used chassis organism in synthetic biology, and can be used as the recombinant microorganism platform. For example, there are libraries of mutants, plasmids, detailed computer models of metabolism and other information available for S. cerevisiae, allowing for rational design of various modules to enhance product yield. Methods are known for making recombinant S. cerevisiae microorganisms. As shown in Example 1, manoyl oxide can be produced in S. cerevisiae strains.

Aspergillus species such as A. oryzae, A. niger and A. sojae are widely used microorganisms in food production and can also be used as the recombinant microorganism platform. Nucleotide sequences are available for genomes of A. nidulans, A. fumigatus, A. oryzae, A. clavatus, A. flavus, A. niger, and A. terreus, allowing rational design and modification of endogenous pathways to enhance flux and increase product yield. Metabolic models have been developed for Aspergillus, as well as transcriptomic studies and proteomics studies. A. niger is cultured for the industrial production of a number of food ingredients such as citric acid and gluconic acid, and thus species such as A. niger are generally suitable for producing manoyl oxide.

E. coli

E. coli, another widely used platform organism in synthetic biology, can also be used as the recombinant microorganism platform. Similar to Saccharomyces, there are libraries of mutants, plasmids, detailed computer models of metabolism and other information available for E. coli, allowing for rational design of various modules to enhance product yield. Methods similar to those described above for Saccharomyces can be used to make recombinant E. coli microorganisms.

Agaricus, Gibberella, and Phanerochaete spp. can be useful because they are known to produce large amounts of isoprenoids in culture. Thus, the terpene precursors for producing large amounts of manoyl oxide are already produced by endogenous genes. Thus, modules comprising recombinant genes for manoyl oxide biosynthesis polypeptides can be introduced into species from such genera without the necessity of introducing mevalonate or MEP pathway genes.

Arxula adeninivorans (Blastobotrys adeninivorans)

Arxula adeninivorans is dimorphic yeast (it grows as budding yeast like the baker's yeast up to a temperature of 42° C., above this threshold it grows in a filamentous form) with unusual biochemical characteristics. It can grow on a wide range of substrates and can assimilate nitrate. It has successfully been applied to the generation of strains that can produce natural plastics or the development of a biosensor for estrogens in environmental samples.

Yarrowia lipolytica

Yarrowia lipolytica is dimorphic yeast (see Arxula adeninivorans) and belongs to the family Hemiascomycetes. The entire genome of Yarrowia lipolytica is known. Yarrowia species is aerobic and considered to be non-pathogenic. Yarrowia is efficient in using hydrophobic substrates (e.g. alkanes, fatty acids, oils) and can grow on sugars. It has a high potential for industrial applications and is an oleaginous microorgamism. Yarrowia lipolyptica can accumulate lipid content to approximately 40% of its dry cell weight and is a model organism for lipid accumulation and remobilization. See e.g., Nicaud, 2012, Yeast 29(10):409-18; Beopoulos et al., 2009, Biochimie 91(6):692-6; Bankar et al., 2009, Appl Microbiol Biotechnol. 84(5):847-65.

Rhodotorula is unicellular, pigmented yeast. The oleaginous red yeast, Rhodotorula glutinis, has been shown to produce lipids and carotenoids from crude glycerol (Saenge et al., 2011, Process Biochemistry 46(1):210-8). Rhodotorula toruloides strains have been shown to be an efficient fed-batch fermentation system for improved biomass and lipid productivity (Li et al., 2007, Enzyme and Microbial Technology 41:312-7).

Rhodosporidium toruloides

Rhodosporidium toruloides is oleaginous yeast and useful for engineering lipid-production pathways (See e.g. Zhu et al., 2013, Nature Commun. 3:1112; Ageitos et al., 2011, Applied Microbiology and Biotechnology 90(4):1219-27).

Candida boidinii

Candida boidinii is methylotrophic yeast (it can grow on methanol). Like other methylotrophic species such as Hansenula polymorpha and Pichia pastoris, it provides an excellent platform for producing heterologous proteins. Yields in a multigram range of a secreted foreign protein have been reported. A computational method, IPRO, recently predicted mutations that experimentally switched the cofactor specificity of Candida boidinii xylose reductase from NADPH to NADH. See, e.g., Mattanovich et al., 2012, Methods Mol Biol. 824:329-58; Khoury et al., 2009, Protein Sci. 18(10):2125-38.

Hansenula polymorpha (Pichia angusta)

Hansenula polymorpha is methylotrophic yeast (see Candida boidinii). It can furthermore grow on a wide range of other substrates; it is thermo-tolerant and can assimilate nitrate (see also Kluyveromyces lactis). It has been applied to producing hepatitis B vaccines, insulin and interferon alpha-2a for the treatment of hepatitis C, furthermore to a range of technical enzymes. See, e.g., Xu et al., 2014, Virol Sin. 29(6):403-9.

Kluyveromyces lactis

Kluyveromyces lactis is yeast regularly applied to the production of kefir. It can grow on several sugars, most importantly on lactose which is present in milk and whey. It has successfully been applied among others for producing chymosin (an enzyme that is usually present in the stomach of calves) for producing cheese. Production takes place in fermenters on a 40,000 L scale. See, e.g., van Ooyen et al., 2006, FEMS Yeast Res. 6(3):381-92.

Pichia pastoris

Pichia pastoris is methylotrophic yeast (see Candida boidinii and Hansenula polymorpha). It provides an efficient platform for producing foreign proteins. Platform elements are available as a kit and it is worldwide used in academia for producing proteins. Strains have been engineered that can produce complex human N-glycan (yeast glycans are similar but not identical to those found in humans). See, e.g., Piirainen et al., 2014, N Biotechnol. 31(6):532-7.

Physcomitrella mosses, when grown in suspension culture, have characteristics similar to yeast or other fungal cultures. This genera can be used for producing plant secondary metabolites, which can be difficult to produce in other types of cells.

Table 1 indicates the identities of the sequences utilized herein.

The invention will be further described in the following examples, which do not limit the scope of the invention described in the claims.

The Examples that follow are illustrative of specific embodiments of the invention, and various uses thereof. They are set forth for explanatory purposes only and are not to be taken as limiting the invention.

TPS2 (SEQ ID NO:6), TPS3 (SEQ ID NO:9), Synechococcus sp. GGPPS7 (SEQ ID NO:2), and A. nidulans GGPPS10 (SEQ ID NO:4) were codon-optimized for expression in S. cerevisiae. The strains produced are shown in Table 2.

A single colony of each strain was inoculated into 500 μL SC-Ura in a 2.2 mL well of a 96 deep well plate. Colonies were grown overnight at 30° C., 400 RPM shaking. 50 μL of each culture were then used to inoculate 500 μL DELFT media, and the cultures were grown for an additional 72 h at 30° C., 400 RPM shaking.

Metabolites were extracted from the culture broth by adding 500 μL 96% ethanol and incubating at 78° C. for 10 min before transferring the samples to fresh tubes and centrifuging at 15,000 g for min. 500 μL of the supernatant was then transferred to a GC vial and was two-phase extracted with 500 mL hexane. Following extraction, each solvent was transferred into new 1.5-mL glass vials and stored at −20° C. For GC-MS analysis, 1 μL of each hexane extract was injected into a Shimadzu GC-MS-QP2010 Ultra. Separation was carried out using an Agilent HP-5MS column (20 m×0.180 mm i.d., 0.18 μm film thickness) with purge flow of 4 mL/min for 1 min, using H₂ as carrier gas. The GC temperature program was as follows: 60° C. for 1 min, ramp at 30° C./min to 180° C., ramp at 10° C./min to 250° C., ramp at 30° C./min to 320° C., and hold for 3 min. Injection temperature was set at 250° C. in splitless mode. Column flow and pressure were set to 5 mL/min and 66.7 kPa, respectively, yielding a linear velocity of 66.5 cm/s. The ion source and MS transfer line were set to 300° C. and 280° C., respectively. MS was set in scan mode from m/z 50 to m/z 350 with a scan width of 0.5 s; solvent cut-off was 4 min.

A representative GC-MS trace of 13R-manoyl oxide produced in an S. cerevisiae strain comprising GGPPS7 (SEQ ID NO:1, SEQ ID NO:2), codon-optimized CfTPS2 (SEQ ID NO:6, SEQ ID NO:7), and codon-optimized CfTPS3 (SEQ ID NO:9, SEQ ID NO:10) is shown in FIG. 3. Manoyl oxide was produced in each of the strains tested. It was also shown that manoyl oxide was produced in all the different background yeast strains 1-12, with highest levels found in background strains 9-12 (FIG. 4). The manoyl oxide levels in strains 9-12 were found to be up to 6- and 3.5-fold higher than in strains 1-4 and strains 5-8, respectively (FIG. 4). Strains comprising GGPPS7 (SEQ ID NO:1, SEQ ID NO:2) produced up to 150-fold more manoyl oxide, compared to strains comprising GGPPS10 (SEQ ID NO:3, SEQ ID NO:4). See strains 10 and 12 in FIG. 4.

Having described the invention in detail and by reference to specific embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims. More specifically, although some aspects of the present invention are identified herein as particularly advantageous, it is contemplated that the present invention is not necessarily limited to these particular aspects of the invention.