Transcriptional Regulation of Wood Formation in Tree Species

Abstract

Wood formation is mediated by a complex developmental program consisting of a number of sequentially occurred processes, including vascular cambial cell division, differentiation of xylem mother cells, cell elongation, secondary wall deposition, programmed cell death, and heartwood formation, all of which are proposed to be coordinated by transcriptional networks. Recent molecular and genetic studies have uncovered a transcriptional network regulating secondary wall biosynthesis during wood formation in tree species. This network encompasses a multileveled feed-forward loop regulatory structure in which the top master transcriptional switches, wood-associated NAC transcription factors (WNDs), together with WND-regulated transcription factors, regulate an array of downstream genes thereby activating the wood biosynthetic program. Genome-wide transcriptome analysis has revealed a number of wood-associated transcription factors, some of which have been proposed to be involved in vascular cambial cell division and secondary xylem differentiation. With the availability of the genome sequence data and the wood-associated gene expression data from tree species, it is expected that we will soon be able to reveal the transcriptional networks regulating various processes of wood formation, the knowledge of which could be applied to genetically engineer wood biomass composition tailored for diverse end uses such as biofuel production.