Distinct and overlapping functions ofMiscanthus sinensisMYB transcription factors SCM1 and MYB103 in lignin biosynthesis

Abstract

38 Cell wall recalcitrance is a major constraint for the exploitation of lignocellulosic biomass as 39 renewable resource for energy and bio-based products. Transcriptional regulators of the lignin 40 biosynthetic pathway represent promising targets for tailoring lignin content and composition in 41 plant secondary cell walls. A wealth of research in model organisms has revealed that 42 transcriptional regulation of secondary cell wall formation is orchestrated by a hierarchical 43 transcription factor (TF) network with NAC TFs as master regulators and MYB factors in the lower 44 tier regulators. However, knowledge about the transcriptional regulation of lignin biosynthesis in 45 lignocellulosic feedstocks, such as Miscanthus, is limited. Here, we characterized two Miscanthus 46 MYB TFs, MsSCM1 and MsMYB103, and compared their transcriptional impact with that of the 47 master regulator MsSND1. In Miscanthus leaves MsSCM1 and MsMYB103 are expressed at 48 growth stages associated with lignification. Ectopic expression of MsSCM1 and MsMYB103 in 49 tobacco leaves was sufficient to trigger secondary cell wall deposition with distinct sugar and lignin 50 composition. Moreover, RNA-seq analysis revealed that the transcriptional responses to MsSCM1 51 and MsMYB103 overexpression showed extensive overlap with the response to MsSND1, but 52 were distinct from each other, underscoring the inherent complexity of secondary cell wall 53 formation. Together, MsSCM1 and MsMYB103 represent interesting targets for manipulations of 54 lignin content and composition in Miscanthus towards tailored biomass. 55 56 157 158 Tissue Staining and Microscopy 159

Targeted plant improvement through genome editing: from laboratory to field

“…Glucose generated from the hydrolysis of cellulose is the main fermentable sugar for bioethanol production and thus the cellulose content of Miscanthus is a major agronomic characteristic in using this grass as an energy crop. The transcription factors MsSCM1 and MsMYB103, which were found to act as regulators of lignin biosynthesis leading to specific lignin qualities, represent interesting targets for lignin content manipulation and composition towards tailored biomass (Golfier et al 2019). GE approaches are not documented yet for this species.…”