SbCOMT (Bmr12) is involved in the biosynthesis of tricin-lignin in sorghum

Authors

Aymerick Eudes, Lawrence Berkeley National LaboratoryFollow
Tanmoy Dutta, Sandia National Laboratories
Kai Deng, Sandia National Laboratories
Nicolas Jacquet, University of Liege
Anagh Sinha, University of California - Berkeley
Veronica T. Benites, Lawrence Berkeley National Laboratory
Edward E.K. Baidoo, Lawrence Berkeley National Laboratory
Aurore Richel, University of Liege
Scott E. Sattler, USDAFollow
Trent R. Northen, Joint Genome Institute
Seema Singh, Sandia National Laboratories
Blake A. Simmons, Lawrence Berkeley National LaboratoryFollow
Dominique Loque, Universite LyonFollow

Document Type

Article

Date of this Version

2017

Citation

Eudes A, Dutta T, Deng K, Jacquet N, Sinha A, Benites VT, et al. (2017) SbCOMT (Bmr12) is involved in the biosynthesis of tricin- lignin in sorghum. PLoS ONE 12(6): e0178160. https://doi.org/10.1371/journal.pone.0178160

Comments

This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.

Abstract

Lignin in plant biomass represents a target for engineering strategies towards the development of a sustainable bioeconomy. In addition to the conventional lignin monomers, namely p-coumaryl, coniferyl and sinapyl alcohols, tricin has been shown to be part of the native lignin polymer in certain monocot species. Because tricin is considered to initiate the polymerization of lignin chains, elucidating its biosynthesis and mechanism of export to the cell wall constitute novel challenges for the engineering of bioenergy crops. Late steps of tricin biosynthesis require two methylation reactions involving the pathway intermediate selgin. It has recently been demonstrated in rice and maize that caffeate O-methyltransferase (COMT) involved in the synthesis syringyl (S) lignin units derived from sinapyl alcohol also participates in the synthesis of tricin in planta. In this work, we validate in sorghum (Sorghum bicolor L.) that the O-methyltransferase responsible for the production of S lignin units (SbCOMT / Bmr12) is also involved in the synthesis of lignin-linked tricin. In particular, we show that biomass from the sorghum bmr12 mutant contains lower level of tricin incorporated into lignin, and that SbCOMT can methylate the tricin precursors luteolin and selgin. Our genetic and biochemical data point toward a general mechanism whereby COMT is involved in the synthesis of both tricin and S lignin units.