OsMYB108 loss‐of‐function enriches p‐coumaroylated and tricin lignin units in rice cell walls

Abstract

Breeding approaches to enrich lignins in biomass could be beneficial to improving the biorefinery process because lignins increase biomass heating value and represent a potent source of valuable aromatic chemicals. However, despite the fact that grasses are promising lignocellulose feedstocks, limited information is yet available for molecular-breeding approaches to upregulate lignin biosynthesis in grass species. In this study, we generated lignin-enriched transgenic rice (Oryza sativa), a model grass species, via targeted mutagenesis of the transcriptional repressor OsMYB108 using CRISPR/Cas9-mediated genome editing. The OsMYB108-knockout rice mutants displayed increased expressions of lignin biosynthetic genes and enhanced lignin deposition in culm cell walls. Chemical and two-dimensional nuclear magnetic resonance (NMR) analyses revealed that the mutant cell walls were preferentially enriched in c-p-coumaroylated and tricin lignin units, both of which are typical and unique components in grass lignins. NMR analysis also showed that the relative abundances of major lignin linkage types were altered in the OsMYB108 mutants.

Improving Lodging Resistance: Using Wheat and Rice as Classical Examples

“…To comprehensively understand the molecular and biological cellular pathway, recent progress in CRISPR/Cas9-mediated genome editing could be a vital tool, as lignin-enriched transgenic rice by using CRISPR/Cas9-targeted mutagenesis of the transcriptional repressor OsMYB108 was achieved. Rice mutants of OsMYB108 -knockout revealed a considerable rise in the expression levels of lignin biosynthetic genes by enhancing lignin deposition in culm cell walls [113]. Hence, this study suggested that scientists should have to further investigate the regulation and complexity of biochemical pathways that counter lodging problem.…”

Differentiation of Tracheary Elements in Sugarcane Suspension Cells Involves Changes in Secondary Wall Deposition and Extensive Transcriptional Reprogramming

“…Blastx searches showed that several of them ( Supplementary Table S7) share high similarity with phenylpropanoid-related MYBs in Arabidopsis, including AtMYB112 (17 genes), a regulator of anthocyanin biosynthesis (Lotkowska et al, 2015), and AtMYB36 (11 genes) that directly and positively regulates the expression of genes involved in the formation of Casparian strips (Kamiya et al, 2015), a root diffusion barrier made of exclusively of lignin (Naseer et al, 2012). In addition, we also found putative orthologs of repressors of phenylpropanoid biosynthesis ( Supplementary Table S7), including the Arabidopsis AtMYB4 and AtMYB7 (eight and three genes, respectively) (Wang et al, 2020) and their corresponding orthologs OsMYB108 in rice (Miyamoto et al, 2019), ZmMYB31/42 in maize (Agarwal et al, 2016), and PvMYB4 in switchgrass (Shen et al, 2012). These MYBs are members of subfamily 4 of the R2R3-MYB family that function as transcriptional repressors of monolignol and flavonoid biosynthesis (Agarwal et al, 2016;Wang et al, 2020).…”

Grass secondary cell walls, Brachypodium distachyon as a model for discovery

“…Repression is also supplied by the MYB G4 clade and are the best characterised in grasses. These include ZmMYB11/31/ 42, PvMYB4/32, and OsMYB108, which are orthologous to AtMYB4/32 (Zhao & Bartley, 2014;Rao & Dixon, 2018;Miyamoto et al, 2019). These were first described in a grass as direct repressors of lignin gene expression (Fornal e et al, 2006;Sonbol et al, 2009).…”