ANAC012, a member of the plant‐specific NAC transcription factor family, negatively regulates xylary fiber development in Arabidopsis thaliana

Abstract

SummaryVascular plants evolved to have xylem that provides physical support for their growing body and serves as a conduit for water and nutrient transport. In a previous study, we used comparative-transcriptome analyses to select a group of genes that were upregulated in xylem of Arabidopsis plants undergoing secondary growth. Subsequent analyses identified a plant-specific NAC-domain transcription factor gene (ANAC012) as a candidate for genetic regulation of xylem formation. Promoter-GUS analyses showed that ANAC012 expression was preferentially localized in the (pro)cambium region of inflorescence stem and root. Using yeast transactivation analyses, we confirmed the function of ANAC012 as a transcriptional activator, and identified an activation domain in the C terminus. Ectopic overexpression of ANAC012 in Arabidopsis (35S::ANAC012 plants) dramatically suppressed secondary wall deposition in the xylary fiber and slightly increased cell-wall thickness in the xylem vessels. Cellulose compositions of the cell wall were decreased in the inflorescent stems and roots of 35S::ANAC012 plants, probably resulting from defects in xylary fiber formation. Our data suggest that ANAC012 may act as a negative regulator of secondary wall thickening in xylary fibers.

Comprehensive Analysis of NAC Domain Transcription Factor Gene Family in Populus trichocarpa

“…Particularly, numerous NAC domain proteins have also been implicated in plant abiotic stresses and defense responses such as drought, salinity, cold shock, mechanical wounding and viral infection [18,20,28,36,39-47]. Recently, accumulating evidences indicated that a considerable portion of NAC domain proteins also play crucial roles in the processes of xylogenesis, fiber development, and wood formation in vascular plants [17,19,21,48-55]. …”

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

“…Recently, it was reported that transcription factors that belong to two similar subclasses of the NAC (NAM, ATAF1/2, and CUC2) domain proteins act as master switches of xylem cell differentiation (Kubo et al, 2005;Zhong et al, 2006;Mitsuda et al, 2005Mitsuda et al, , 2007Ko et al, 2007). VASCULAR-RELATED NAC-DOMAIN6 (VND6) and VND7, which form a subclade with VND1 to VND5, are expressed preferentially in potential metaxylem vessels and protoxylem vessels, respectively, and initiate their differentiation (Kubo et al, 2005).…”

“…VASCULAR-RELATED NAC-DOMAIN6 (VND6) and VND7, which form a subclade with VND1 to VND5, are expressed preferentially in potential metaxylem vessels and protoxylem vessels, respectively, and initiate their differentiation (Kubo et al, 2005). By contrast, NAC SECONDARY WALL THICKENING PROMOTING FACTOR (NST1) and SECONDARY WALL-ASSOCIATED NAC DOMAIN PROTEIN1 (SND1), also known as ARABIDOPSIS NAC DOMAIN CONTAINING PRO-TEIN12 or NST3, which belong to the subclade closest to the VND family, are involved in xylem fiber cell differentiation (Zhong et al, 2006;Mitsuda et al, 2005Mitsuda et al, , 2007Ko et al, 2007). Indeed, nst1 snd1 double knockout plants show suppressed xylem fiber development (Mitsuda et al, 2007).…”

A structural view of the conserved domain of rice stress-responsive NAC1

“…NAC1 was found to act downstream of TIR1 and activate the expression of two auxinresponsive genes DBP and AIR3, therefore promoting lateral root development (Xie et al, 2000). VND6 and VND7 are involved in xylem formation (Kubo et al, 2005;Demura and Fukuda, 2007;Du and Groover, 2010), while ANAC012 functions in xylary fiber development (Ko et al, 2007). Several NAC members including SND1, NST1 and NST3 were found to regulate secondary wall synthesis (Zhong et al, 2006;Mitsuda et al, 2007;Zhong et al, 2007a, b;McCarthy et al, 2009).…”