Modified expression of ZmMYB167 in Brachypodium distachyon and Zea mays leads to increased cell wall lignin and phenolic content

Abstract

One of the challenges to enable targeted modification of lignocellulosic biomass from grasses for improved biofuel and biochemical production lies within our limited understanding of the transcriptional control of secondary cell wall biosynthesis. Here, we investigated the role of the maize MYB transcription factor ZmMYB167 in secondary cell wall biosynthesis and how modified ZmMYB167 expression in two distinct grass model species affects plant biomass and growth phenotypes. Heterologous expression of ZmMYB167 in the C 3 model system Brachypodium led to mild dwarf phenotypes, increased lignin (~7% to 13%) and S-lignin monomer (~11% to 16%) content, elevated concentrations of cell wall-bound p -coumaric acid (~15% to 24%) and reduced biomass sugar release (~20%) compared to controls. Overexpression of ZmMYB167 in the C 4 model system Zea mays increased lignin (~4% to 13%), p -coumaric acid (~8% to 52%) and ferulic acid (~13% to 38%) content but did not affect plant growth and development nor biomass recalcitrance. Taken together, modifying ZmMYB167 expression represents a target to alter lignin and phenolic content in grasses. The ZmMYB167 expression-induced discrepancies in plant phenotypic and biomass properties between the two grass model systems highlight the challenges and opportunities for MYB transcription factor-based genetic engineering approaches of grass biomass.

MYB Transcription Factors as Regulators of Secondary Metabolism in Plants

“…These TFs contain EgMYB2 from Eucalyptus gunnii [102], PtoMYB216, PtrMYB20, and PtrMYB3 from Populus spp. [104,105], ZmMYB167 from Z. mays [106], PtMYB1 and PtMYB4 from Pinus taeda [107,108], and AtMYB75 and AtMYB61 from A. thaliana [28,109].…”

The GT factor ZmGT-3b mediates growth–defense tradeoff by regulating photosynthesis and defense response1

“…CC-BY 4.0 International license made available under a (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is lignin content to 13% in maize without affecting plant growth or development (Bhatia et al, 2019). Besides MYB TFs, some NAC (Zhong et al, 2007) and WRKY TFs also regulate lignin biosynthesis by modulating the expression of cell wall synthesis-related genes (Gallego- .…”

“…Five maize MYB TFs (ZmMYB2, ZmMYB8, ZmMYB31, ZmMYB39, ZmMYB42) function in lignin biosynthesis by controlling ZmCOMT expression (Fornale et al, 2006). Overexpression of ZmMYB167 increased lignin content to 13% in maize without affecting plant growth or development (Bhatia et al, 2019). Besides MYB TFs, some NAC (Zhong et al, 2007) and WRKY TFs also regulate lignin biosynthesis by modulating the expression of cell wall synthesis-related genes (Gallego- .…”

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

“…However, in sorghum, rice, and switchgrass (Panicum virgatum), ectopic expression of OsMYB58/63, PvMYB58/63, and the sorghum orthologue SbMYB60 results in the activation of cellulose and hemicellulose genes as well as lignin (Noda et al, 2015;Scully et al, 2016;Rao et al, 2019). A potential orthologue to OsMYB42/ 85, ZmMYB167, was overexpressed in maize and heterologously in B. distachyon to similar effect (Bhatia et al, 2019). Similar functions have been resolved for the A. thaliana and rice orthologues AtMYB61 and OsMYB61 as well as AtMYB103 and OsMYB103 (Hirano et al, 2013;Huang et al, 2015;O'Malley et al, 2016;Zhao et al, 2019).…”