Characterization of O-methyltransferases in the biosynthesis of phenylphenalenone phytoalexins based on the telomere-to-telomere gapless genome of Musella lasiocarpa

Abstract

Phenylphenalenones (PhPNs), phytoalexins in wild bananas (Musaceae), are known to act against various pathogens. However, the abundance of PhPNs in many Musaceae plants of economic importance is low. Knowledge of the biosynthesis of PhPNs and the application of biosynthetic approaches to improve their yield is vital for fighting banana diseases. However, the processes of PhPN biosynthesis, especially those involved in methylation modification, remain unclear. Musella lasiocarpa is a herbaceous plant belonging to Musaceae, and due to the abundant PhPNs, their biosynthesis in M. lasiocarpa has been the subject of much attention. In this study, we assembled a telomere-to-telomere gapless genome of M. lasiocarpa as the reference, and further integrated transcriptomic and metabolomic data to mine the candidate genes involved in PhPN biosynthesis. To elucidate the diversity of PhPNs in M. lasiocarpa, three screened O-methyltransferases (Ml01G0494, Ml04G2958, and Ml08G0855) by phylogenetic and expressional clues were subjected to in vitro enzymatic assays. The results show that the three were all novel O-methyltransferases involved in the biosynthesis of PhPN phytoalexins, among which Ml08G0855 was proved to function as a multifunctional enzyme targeting multiple hydroxyl groups in PhPN structure. Moreover, we tested the antifungal activity of PhPNs against Fusarium oxysporum and found that the methylated modification of PhPNs enhanced their antifungal activity. These findings provide valuable genetic resources in banana breeding and lay a foundation for improving disease resistance through molecular breeding.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (grants 32070360, 32200326, and 22207047), the Natural Science Foundation of Jiangsu Province (BK20220752 and BK20220749), and the Jiangsu Institute of Botany Talent Fund (JIBTF202304). We thank Professor Zefu Wang (Nanjing Forestry University) for critical reading of the manuscript and Emily Wheeler for editorial assistance.

Author contributions

Y.C. and P.R.L. designed the experiments. W.L.Z. and J.Z.W. performed the experiments. M.T., S.Y.H., Z.Y.W., and G.Y.L. performed genomic analysis. S.X. and B.W. carried out antibacterial assays. L.T., R.Y.W., and B.Y.F. isolated and characterized the compounds. W.L.Z., J.Y.X., and Y.C. wrote the paper. C.P., H.L., and X.F. reviewed and revised the paper. All authors contributed to discussion of the manuscript.

Data availability

Reference genome data and transcriptome sequence reads are available in GenBank under project number PRJNA1009687.

Conflict of interest

The authors declare that there are no conflicts of interest.

Supplementary data

Supplementary data are available at Horticulture Research online.

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