SND1, a NAC Domain Transcription Factor, Is a Key Regulator of Secondary Wall Synthesis in Fibers ofArabidopsis

Abstract

Secondary walls in fibers and tracheary elements constitute the most abundant biomass produced by plants. Although a number of genes involved in the biosynthesis of secondary wall components have been characterized, little is known about the molecular mechanisms underlying the coordinated expression of these genes. Here, we demonstrate that the Arabidopsis thaliana NAC (for NAM, ATAF1/2, and CUC2) domain transcription factor, SND1 (for secondary wall-associated NAC domain protein), is a key transcriptional switch regulating secondary wall synthesis in fibers. We show that SND1 is expressed specifically in interfascicular fibers and xylary fibers in stems and that dominant repression of SND1 causes a drastic reduction in the secondary wall thickening of fibers. Ectopic overexpression of SND1 results in activation of the expression of secondary wall biosynthetic genes, leading to massive deposition of secondary walls in cells that are normally nonsclerenchymatous. In addition, we have found that SND1 upregulates the expression of several transcription factors that are highly expressed in fibers during secondary wall synthesis. Together, our results reveal that SND1 is a key transcriptional activator involved in secondary wall biosynthesis in fibers.

SND1 Transcription Factor-Directed Quantitative Functional Hierarchical Genetic Regulatory Network in Wood Formation in Populus trichocarpa

“…Of these 138 genes, only seven (two TF and five enzyme coding genes; i.e., homologs of Ptr-MYB002 and Integrase-type DNA binding superfamily protein; see Supplemental Table 3 online) were found in our 76 direct targets of Ptr-SND1-B1 in P. trichocarpa differentiating xylem, demonstrating that leaf and xylem cells behave quite differently in the transcriptome response to SND regulation. In fact, the biological function of At-SND1 in regulating the 138 genes in leaf cells is unclear because, in the leaf tissue, At-SND1 was not detected (Zhong et al, 2006). By contrast, Ptr-SND1-B1 is abundantly and specifically expressed in P. trichocarpa differentiating xylem (Li et al, 2012).…”

Genetic architecture of wood properties based on association analysis and co‐expression networks in white spruce

“…PgNAC‐7 and these three MYBs were proposed by Duval et al . (2014) to form a regulatory network similar to the SND1 network defined in Arabidopsis (Zhong et al ., 2006) that is conserved in poplar (Lin et al ., 2013; Wang et al ., 2014). The regulation of lignin biosynthesis by members of the conserved SND1 transcriptional network has been well documented in conifer trees (Patzlaff et al ., 2003a,b; Bomal et al ., 2008, 2014).…”

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

“…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). Notably, a few members have been reported to participate in multiple processes, which might be a general rule for most NAC proteins.…”