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Zhang W, Forester NT, Chettri P, Heilijgers M, Mace WJ, Maes E, Morozova Y, Applegate ER, Johnson RD, Johnson LJ. Characterization of the Biosynthetic Gene Cluster for the Ribosomally Synthesized Cyclic Peptide Epichloëcyclins in Epichloë festucae. J Agric Food Chem 2023; 71:13965-13978. [PMID: 37704203 PMCID: PMC10540207 DOI: 10.1021/acs.jafc.3c03073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 08/14/2023] [Accepted: 08/16/2023] [Indexed: 09/15/2023]
Abstract
The various grass-induced epichloëcyclins of the Epichloë spp. are ribosomally synthesized and post-translationally modified peptides (RiPPs), produced as small, secreted cyclopeptides from a single gene, gigA. Here, four clustered and coregulated genes (gigA, gigB, gigC, and kexB) with predicted roles in epichloëcyclin production in Epichloë festucae were evaluated through gene disruption. Subsequent chemical analysis indicates that GigB is a DUF3328 domain-containing protein associated with cyclization of epichloëcyclins; GigC is a methyltransferase enzyme responsible for N-methylation of desmethylepichloëcyclins; and KexB is a subtilisin-like enzyme, partly responsible for the propeptide cleavage of epichloëcyclin intermediates. Symbiotic effects on the host phenotype were not observed for gigA, gigC, or kexB mutants, although ΔgigB infection correlated with increased host tiller height and biomass, while only ΔkexB exhibited an effect on endophyte morphology. Disrupting epichloëcyclin biosynthesis showed negligible influence on the biosynthesis of E. festucae-associated alkaloids. Epichloëcyclins may perform other secondary metabolism functions in Epichloë and other fungi.
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Affiliation(s)
- Wei Zhang
- Grasslands
Research Centre, AgResearch Limited, Palmerston North 4442, New Zealand
| | - Natasha T. Forester
- Grasslands
Research Centre, AgResearch Limited, Palmerston North 4442, New Zealand
| | - Pranav Chettri
- Grasslands
Research Centre, AgResearch Limited, Palmerston North 4442, New Zealand
| | - Maurice Heilijgers
- Grasslands
Research Centre, AgResearch Limited, Palmerston North 4442, New Zealand
| | - Wade J. Mace
- Grasslands
Research Centre, AgResearch Limited, Palmerston North 4442, New Zealand
| | - Evelyne Maes
- Lincoln
Research Centre, AgResearch Limited, Lincoln 7608, New Zealand
| | - Yulia Morozova
- Grasslands
Research Centre, AgResearch Limited, Palmerston North 4442, New Zealand
| | - Emma R. Applegate
- Grasslands
Research Centre, AgResearch Limited, Palmerston North 4442, New Zealand
| | - Richard D. Johnson
- Grasslands
Research Centre, AgResearch Limited, Palmerston North 4442, New Zealand
| | - Linda J. Johnson
- Grasslands
Research Centre, AgResearch Limited, Palmerston North 4442, New Zealand
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Kortbeek RWJ, Galland MD, Muras A, van der Kloet FM, André B, Heilijgers M, van Hijum SAFT, Haring MA, Schuurink RC, Bleeker PM. Natural variation in wild tomato trichomes; selecting metabolites that contribute to insect resistance using a random forest approach. BMC Plant Biol 2021; 21:315. [PMID: 34215189 PMCID: PMC8252294 DOI: 10.1186/s12870-021-03070-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 05/20/2021] [Indexed: 05/13/2023]
Abstract
BACKGROUND Plant-produced specialised metabolites are a powerful part of a plant's first line of defence against herbivorous insects, bacteria and fungi. Wild ancestors of present-day cultivated tomato produce a plethora of acylsugars in their type-I/IV trichomes and volatiles in their type-VI trichomes that have a potential role in plant resistance against insects. However, metabolic profiles are often complex mixtures making identification of the functionally interesting metabolites challenging. Here, we aimed to identify specialised metabolites from a wide range of wild tomato genotypes that could explain resistance to vector insects whitefly (Bemisia tabaci) and Western flower thrips (Frankliniella occidentalis). We evaluated plant resistance, determined trichome density and obtained metabolite profiles of the glandular trichomes by LC-MS (acylsugars) and GC-MS (volatiles). Using a customised Random Forest learning algorithm, we determined the contribution of specific specialised metabolites to the resistance phenotypes observed. RESULTS The selected wild tomato accessions showed different levels of resistance to both whiteflies and thrips. Accessions resistant to one insect can be susceptible to another. Glandular trichome density is not necessarily a good predictor for plant resistance although the density of type-I/IV trichomes, related to the production of acylsugars, appears to correlate with whitefly resistance. For type VI-trichomes, however, it seems resistance is determined by the specific content of the glands. There is a strong qualitative and quantitative variation in the metabolite profiles between different accessions, even when they are from the same species. Out of 76 acylsugars found, the random forest algorithm linked two acylsugars (S3:15 and S3:21) to whitefly resistance, but none to thrips resistance. Out of 86 volatiles detected, the sesquiterpene α-humulene was linked to whitefly susceptible accessions instead. The algorithm did not link any specific metabolite to resistance against thrips, but monoterpenes α-phellandrene, α-terpinene and β-phellandrene/D-limonene were significantly associated with susceptible tomato accessions. CONCLUSIONS Whiteflies and thrips are distinctly targeted by certain specialised metabolites found in wild tomatoes. The machine learning approach presented helped to identify features with efficacy toward the insect species studied. These acylsugar metabolites can be targets for breeding efforts towards the selection of insect-resistant cultivars.
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Affiliation(s)
- Ruy W J Kortbeek
- Green Life Science Research Cluster, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 XH, Amsterdam, The Netherlands
| | - Marc D Galland
- Green Life Science Research Cluster, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 XH, Amsterdam, The Netherlands
| | - Aleksandra Muras
- Green Life Science Research Cluster, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 XH, Amsterdam, The Netherlands
| | - Frans M van der Kloet
- Data Analysis Group, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 XH, Amsterdam, The Netherlands
| | - Bart André
- Enza Zaden Research & Development B.V, Haling 1E, 1602 DB, Enkhuizen, The Netherlands
| | - Maurice Heilijgers
- Green Life Science Research Cluster, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 XH, Amsterdam, The Netherlands
| | - Sacha A F T van Hijum
- Radboud University Medical Center, Bacterial Genomics Group, Geert Grooteplein Zuid 26-28, 6525 GA, Nijmegen, The Netherlands
| | - Michel A Haring
- Green Life Science Research Cluster, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 XH, Amsterdam, The Netherlands
| | - Robert C Schuurink
- Green Life Science Research Cluster, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 XH, Amsterdam, The Netherlands
| | - Petra M Bleeker
- Green Life Science Research Cluster, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 XH, Amsterdam, The Netherlands.
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