Transcriptional regulation of secondary wall formation controlled by NAC domain proteins

Abstract

The plant vascular tissue consists of phloem and xylem. Phloem transports nutrients such as amino acids and sucrose. Xylem functions in the conduction of water and minerals throughout the plant and also supports the plant body. One of the characteristic features of xylem cells is a secondary wall structure between plasma membrane and (primary) cell wall. Studies on differentiation of xylem cells have been considered a good model system for the analysis of cell differentiation in higher plants because there are several well-established in vitro induction systems, in which isolated cells or suspension cultured cells from various plants transdifferentiate into xylem cells (reviewed in Fukuda 1996(reviewed in Fukuda , 2004 Turner et al. 2007). Recent interest in biofuels has raised the possibility that a better understanding of xylem development can be utilized for the improvement of plant biomass, since major portions of wood, which represents one of important sources of woody biomass, is mainly composed of two types of xylem cells, xylem vessels and fiber cells. Moreover, main components of the secondary wall are polysaccharides, cellulose, and hemicellulose, which are expected to be good starting materials for the production of bioethanol and bioplastics.Transcription factors are proteins that have function in controlling the expression of target genes quantitatively, temporally, and spatially. To date, genetic analyses have revealed a number of transcription factors regulating vascular development (reviewed in Ariel et al. 2007;Carlsbecker and Helariutta 2005;Demura and Fukuda 2007). Moreover, reverse genetic approaches have been successful in isolating several NAC (which stands for NAM, ATAF1/2 and CUC2) domain transcription factors that control the specification of xylem cells accompanied by secondary wall formation. In this review, we summarize the function and regulation of the NAC domain proteins controlling secondary wall formation.VND/NST/SND1 subfamily of NAC domain proteins regulate secondary wall formation Previously, we established in vitro transdifferentiation systems, in which zinnia mesophyll cells and Arabidopsis suspension cells could synchronously transdifferentiate into tracheary elements at a high frequency. By using microarray analysis we identified a number of genes whose expression is elevated during the transdifferentiation processes (Demura et al. 2002;Kubo et al. 2005), including the following genes belonging to a subfamily of the NAC transcription factor family: zinnia Ze567 and Arabidopsis VND1 to VND7 (Figure 1). Abstract Woody cells develop secondary wall structure that mainly consists of polysaccharides (cellulose and hemicellulose) and lignin. These components are expected to be new sources of biofuels and biomaterials. Therefore, it is important to understand the molecular mechanism underlying secondary wall formation and how it contributes to plant biomass. Plant-specific NAC domain transcription factor family has been shown to be involved in diverse biological functions. Recen...

Proteomic analysis of xylem vessel cell differentiation in VND7-inducible tobacco BY-2 cells by two-dimensional gel electrophoresis

“…In vitro inducible systems involving Arabidopsis thaliana suspension cells have become an increasingly powerful tool when combined with molecular genetics. This approach has led to the discovery of VASCULAR-RELATED NAC-DOMAIN (VND) proteins; these plant-specific NAC domain transcription factor are key regulators of xylem vessel cell differentiation (Kubo et al 2005;Yamaguchi et al 2008;Yamaguchi and Demura 2010). Overexpression analysis of VND genes revealed that VND7 and VND6 initiate the differentiation of protoxylem-type and metaxylem-type vessel cells, respectively (Kubo et al 2005;.…”

“…Transcriptomic analyses of Arabidopsis VND6 and VND7 overexpressors have uncovered a set of direct target genes of VND6 and VND7, including genes required for deposition of the SCW and progression of PCD (Ohashi-Ito et al 2010;Yamaguchi et al , 2011Zhong et al 2010). Based on the results of transcriptomic analysis, the evolutionarily conserved VND-based transcriptional network is currently thought to form the basis of xylem vessel cell differentiation Kubo et al 2005;Nakano et al 2015;Yamaguchi and Demura 2010;Zhong et al 2010).…”

A Missense Mutation in the Glucosamine-6-Phosphate N-Acetyltransferase–Encoding Gene Causes Temperature-Dependent Growth Defects and Ectopic Lignin Deposition in Arabidopsis

“…Expression of these genes is activated directly by a specific kind of MYB transcription factor (Patzlaff et al, 2003;Zhou et al, 2009;Zhao and Dixon, 2011). NAC domain proteins, such as VASCULAR-RELATED NAC-DOMAIN6 (VND6) and VND7 in Arabidopsis thaliana, which can direct the whole program of cell differentiation (Kubo et al, 2005;Yamaguchi and Demura, 2010), are key regulators that act upstream of the MYB factors.…”

An NAC Transcription Factor Controls Ethylene-Regulated Cell Expansion in Flower Petals

“…The NAC superfamily can be divided into at least seven subfamilies (Rushton et al, 2008), and the function of NAC genes is typically subfamily specific. In Arabidopsis, members of the NAM subfamily CUC1/CUC2/CUC3 are well known as regulators involved in shoot apical meristem formation and cotyledon separation during embryogenesis (Aida et al, 1997;Olsen et al, 2005), whereas members of the Vascular-related NACDomain protein/NAC Secondary wall Thickening promoting factor/Secondary wall-associated NACDomain protein (VND/NST/SND1) subfamily are typically involved in regulating secondary wall formation (Yamaguchi and Demura, 2010). Previous reports have indicated that several NAC genes may be regulated by ethylene.…”