ZmMYB31 directly represses maize lignin genes and redirects the phenylpropanoid metabolic flux

Abstract

SUMMARYFew regulators of phenylpropanoids have been identified in monocots having potential as biofuel crops. Here we demonstrate the role of the maize (Zea mays) R2R3-MYB factor ZmMYB31 in the control of the phenylpropanoid pathway. We determined its in vitro consensus DNA-binding sequence as ACC T / A ACC, and chromatin immunoprecipitation (ChIP) established that it interacts with two lignin gene promoters in vivo. To explore the potential of ZmMYB31 as a regulator of phenylpropanoids in other plants, its role in the regulation of the phenylpropanoid pathway was further investigated in Arabidopsis thaliana. ZmMYB31 downregulates several genes involved in the synthesis of monolignols and transgenic plants are dwarf and show a significantly reduced lignin content with unaltered polymer composition. We demonstrate that these changes increase cell wall degradability of the transgenic plants. In addition, ZmMYB31 represses the synthesis of sinapoylmalate, resulting in plants that are more sensitive to UV irradiation, and induces several stress-related proteins. Our results suggest that, as an indirect effect of repression of lignin biosynthesis, transgenic plants redirect carbon flux towards the biosynthesis of anthocyanins. Thus, ZmMYB31 can be considered a good candidate for the manipulation of lignin biosynthesis in biotechnological applications.

The MYB182 Protein Down-Regulates Proanthocyanidin and Anthocyanin Biosynthesis in Poplar by Repressing Both Structural and Regulatory Flavonoid Genes

“…This would suggest that DNA binding is also essential for its repressor function (Jin et al, 2000). Other subgroup 4 MYB factors are reported to directly bind target gene promoters (Jin et al, 2000;Fornalé et al, 2010;Shen et al, 2012;Bomal et al, 2014). We cannot rule out that mutation of the MYB182 bHLH-binding site also might have affected its DNA-binding ability, since Baudry et al (2004) had shown that the Arabidopsis MYB TT2 can only bind to its target gene promoter in yeast (Saccharomyces cerevisiae) in the presence of a bHLH or WDR factor.…”

MYB transcription factor genes as regulators for plant responses: an overview

“…ZmMYB31 downregulated several genes involved in the synthesis of monolignols and transgenic plants were dwarf and showed a significantly reduced lignin content with unaltered polymer composition. In addition, ZmMYB31 repressed the synthesis of sinapoylmalate and phenylpropanoid resulting in plants that were more sensitive to UV irradiation, and induced several stress-related proteins (Fornale et al 2010). …”

A Kelch domain-containing F-box coding gene negatively regulates flavonoid accumulation in Cucumis melo L.

“…Zea mays R2R3-MYB transcription factor (ZmMYB31), a direct repressor of caffeic acid 3-O-methyltransferase and Arabidopsis ferulate-5-hydroxylase genes, overexpression in Arabidopsis results in reduction in sinaopylmalate and lignin accumulation while enhancing accumulation of ferulic acid, coumaric acid, and anthocyanins (Fornalé et al, 2010). In addition, the colorless fruit peel y mutant in tomato was found to be a mutation causing down-regulation of SlMYB12, a transcription factor that acts as a positive regulator of an array of phenylpropanoid structural genes.…”