Arabidopsis VASCULAR-RELATED NAC-DOMAIN6 Directly Regulates the Genes That Govern Programmed Cell Death and Secondary Wall Formation during Xylem Differentiation  

Abstract

Xylem consists of three types of cells: tracheary elements (TEs), parenchyma cells, and fiber cells. TE differentiation includes two essential processes, programmed cell death (PCD) and secondary cell wall formation. These two processes are tightly coupled. However, little is known about the molecular mechanisms underlying these processes. Here, we show that VASCULAR-RELATED NAC-DOMAIN6 (VND6), a master regulator of TEs, regulates some of the downstream genes involved in these processes in a coordinated manner. We first identified genes that are expressed downstream of VND6 but not downstream of SECONDARY WALL-ASSOCIATED NAC DOMAIN PROTEIN1 (SND1), a master regulator of xylem fiber cells, using transformed suspension culture cells in microarray experiments. We found that VND6 and SND1 governed distinct aspects of xylem formation, whereas they regulated a number of genes in common, specifically those related to secondary cell wall formation. Genes involved in TE-specific PCD were upregulated only by VND6. Moreover, we revealed that VND6 directly regulated genes that harbor a TE-specific cis-element, TERE, in their promoters. Thus, we found that VND6 is a direct regulator of genes related to PCD as well as to secondary wall formation.

RICE SALT SENSITIVE3 binding to bHLH and JAZ factors mediates control of cell wall plasticity in the root apex

“…In Arabidopsis, MYB-type (MYB46, MYB58, and MYB63) and NAC-type (SND1, SND2, VND6, VND7, NST1, and NST2) transcription factors function as positive regulators of secondary cell wall synthesis. [18][19][20][21][22][23][24] Some rice NAC-type transcription factors have also been described to control secondary cell wall metabolism. 25 In rss3, several NAC genes that belong to the subfamily, in which Arabidopsis NST1 and SND2 are classified, were upregulated (Fig.…”

ATL54, a RING-H2 domain protein selected by a gene co-expression network analysis, is associated with secondary cell wall formation in Arabidopsis

“…For example, in Arabidopsis, VASCULAR-RELATED NAC-DOMAIN6 (VND6) and VND7 regulate the development of metaxylem and protoxylem vessel elements, respectively (Kubo et al 2005;Yamaguchi et al 2008), while NAC SECONDARY WALL THICKENING PROMOTING FACTOR1 (NST1) and NST3 [also called SECONDARY WALL-ASSOCIATED NAC DOMAIN PROTEIN1 (SND1) or ARABIDOPSIS NAC DOMAIN CONTAINING PROTEIN012 (ANAC012)] redundantly act as master switches that turn on secondary wall formation in fibers (Mitsuda et al 2007;Zhong et al 2006). MYB46 and MYB83 are direct downstream transcription factors of VND6, VND7, NST1, and NST3/SND1/ANAC012 (McCarthy et al 2009;Ohashi-Ito et al 2010;Yamaguchi et al 2011). MYB46 and MYB83 can activate biosynthetic pathways for cellulose, xylan, and lignin, the three major secondary wall components (Ko et al 2009;McCarthy et al 2009;Nakano et al 2010;Zhong et al 2007).…”

Formation of plant tracheary elements in vitro – a review

“…The functional suppression of VND6 and VND7 causes defects in the formation of vessel elements (Kubo et al 2005;Yamaguchi et al, 2008). Subsequently, Ohashi-Ito et al (2010) found that VND6 is a direct regulator of genes related to programmed cell death as well as to secondary wall formation. These results strongly suggest that VND6 and VND7 act as key regulators of xylem vessel differentiation.…”

“…Three common methods used to transform xylogenic lines are biolistic particle delivery (Ito and Fukuda 2002;Möller et al 2003;Wagner et al 2012), Agrobacterium tumefaciens-mediated transformation (Pyo et al 2007;Pesquet et al 2010;Ohashi-Ito et al 2010) and electroporation (Endo et al 2008).…”