EgMYB2, a new transcriptional activator from Eucalyptus xylem, regulates secondary cell wall formation and lignin biosynthesis

Abstract

SummaryEgMYB2, a member of a new subgroup of the R2R3 MYB family of transcription factors, was cloned from a library consisting of RNA from differentiating Eucalyptus xylem. EgMYB2 maps to a unique locus on the Eucalyptus grandis linkage map and co-localizes with a quantitative trait locus (QTL) for lignin content. Recombinant EgMYB2 protein was able to bind specifically the cis-regulatory regions of the promoters of two lignin biosynthetic genes, cinnamoyl-coenzyme A reductase (CCR) and cinnamyl alcohol dehydrogenase (CAD), which contain MYB consensus binding sites. EgMYB2 was also able to regulate their transcription in both transient and stable expression assays. Transgenic tobacco plants over-expressing EgMYB2 displayed phenotypic changes relative to wild-type plants, among which were a dramatic increase in secondary cell wall thickness, and an alteration of the lignin profiles. Transcript abundance of genes encoding enzymes specific to lignin biosynthesis was increased to varying extents according to the position of individual genes in the pathway, whereas core phenylpropanoid genes were not significantly affected. Together these results suggest a role for EgMYB2 in the co-ordinated control of genes belonging to the monolignol-specific pathway, and therefore in the biosynthesis of lignin and the regulation of secondary cell wall formation.

Small-interfering RNAs from natural antisense transcripts derived from a cellulose synthase gene modulate cell wall biosynthesis in barley

“…Transcriptional switches for programs involving different cell wall gene networks involving a switch from primary to secondary wall include both NAC-domain (10) and Myb transcription factors (11). The lack of secondary wall formation but not cellular specification when these and other NAC-domain containing proteins are repressed and the induction of ectopic secondary walls in overexpressing lines provide strong evidence for control of cell wall gene networks (10).…”

Progress in Myrtaceae genetics and genomics: Eucalyptus as the pivotal genus

“…Even though array-based studies are useful for discovering candidate genes, functional studies can confirm the role of a gene in controlling a trait. Goicoechea et al (2005) characterized the role of EgMYB2, a transcriptional activator identified from differentiating xylem from Eucalyptus. Using proteinbinding analyses, they showed that EgMYB2 specifically binds to the promoters of CCR and CAD, the two terminal genes in the lignin biosynthetic pathway, and regulates their expression.…”

An R2R3-type transcription factor gene AtMYB59 regulates root growth and cell cycle progression in Arabidopsis

“…Several MYB proteins may be involved in secondary metabolism [7][8][9]. AtMYB0/GL1 is required for leaf trichome differentiation [10].…”