Advances in Regulation of Xylem Secondary Cell Wall Thickening in Plants

The xylem is a compound tissue in vascular plants, responsible for transportation of soil moisture and soluble substances. It is composed of 3 parts: tracheary element, xylem parenchyma and xylon. Tracheary element and xylon cell can undergo secondary wall thickening and provide the necessary support for plant growth and development. The secondary cell wall thickening is a complex and orderly process, which is jointly regulated by multiple transcription factors, and the NAC−MYB based transcription regulatory network plays the key role in this process. The NAC transcription factor family can be divided into VND gene family, NST1/NST3 transcription factor and NST1/NST2 transcription factor according to their regulatory positions, and directly regulate the expression of downstream MYB transcription factor family, affecting the thickening of secondary cell walls. Recent studies have accumulated more evidences to support this regulatory network. This paper aims to reorganize and sort out the recent relevant results through integrating the studies in Arabidopsis thaliana, Oryza sativa, Populus sp. and other model plants, in order to better understand the transcriptional regulation during the thickening of the xylem secondary wall.