A MYB/ZML Complex Regulates Wound-Induced Lignin Genes in Maize

Abstract

Lignin is an essential polymer in vascular plants that plays key structural roles in vessels and fibers. Lignification is induced by external inputs such as wounding, but the molecular mechanisms that link this stress to lignification remain largely unknown. In this work, we provide evidence that three maize (Zea mays) lignin repressors, MYB11, MYB31, and MYB42, participate in wound-induced lignification by interacting with ZML2, a protein belonging to the TIFY family. We determined that the three R2R3-MYB factors and ZML2 bind in vivo to AC-rich and GAT(A/C) cis-elements, respectively, present in a set of lignin genes. In particular, we show that MYB11 and ZML2 bind simultaneously to the AC-rich and GAT(A/C) cis-elements present in the promoter of the caffeic acid O-methyl transferase (comt) gene. We show that, like the R2R3-MYB factors, ZML2 also acts as a transcriptional repressor. We found that upon wounding and methyl jasmonate treatments, MYB11 and ZML2 proteins are degraded and comt transcription is induced. Based on these results, we propose a molecular regulatory mechanism involving a MYB/ZML complex in which wound-induced lignification can be achieved by the derepression of a set of lignin genes.

Synthesis and Functions of Jasmonates in Maize

“…Another physical defense is lignification, which strengthens cell walls to increase resistance against insect mastication. Recently, treatment with MeJA resulted in degradation of repressors of the lignin biosynthetic pathway [115]. Direct chemical defense responses include the production of metabolites that intoxicate or repel herbivores or suppress nutrient acquisition (e.g., protease inhibitors).…”

A Key Role for Apoplastic H2O2 in Norway Spruce Phenolic Metabolism

“…The Tify transcription factor family has been connected to a variety of abiotic and biotic stresses and also to development (Zhang et al, 2015). In maize (Zea mays), ZML2, a Tify family member, and MYB11 together repress COMT expression (Vélez-Bermúdez et al, 2015).…”

PtoMYB156 is involved in negative regulation of phenylpropanoid metabolism and secondary cell wall biosynthesis during wood formation in poplar

“…Since PtoMYB156 shares significant similarity with other phenylpropanoid/lignin biosynthesis repressors such as AtMYB422, AmMYB30855, ZmMYB4225, ZmMYB3124 and ZmMYB1119, we investigated whether PtoMYB156 could also negatively regulate the biosynthesis of phenylpropanoid compounds in transgenic plants. Quantification analysis showed a strong reduction in accumulation of total phenolics, flavonols, anthocyanins and soluble PAs in 35S:PtoMYB156 lines compared with the wild type (Fig.…”

“…These transcription factors have been shown to be functional orthologs of Arabidopsis MYB46/83, and overexpression of PtMYB4 and EgMYB2 resulted in ectopic lignification in tobacco and Arabidopsis , respectively1317. There are also many R2R3 MYB transcription factors that directly bind to AC cis -elements (AC-I, ACCTACC; AC-II, ACCAACC, and AC-III, ACCTAAC) in lignin biosynthetic gene promoters to positively and negatively regulate lignin synthesis819. Among of them, AtMYB58 and AtMYB6320, AtMYB856 and AtMYB8321, and PtMYB118 have been identified as transcriptional activators, and AtMYB422, AtMYB3223, ZmMYB3124, ZmMYB4224, PvMYB426, EgMYB127, ZmMYB1119, VvMYBC2-L1/L328 as repressors.…”