SND1, a NAC domain transcription factor, is a key regulator of secondary wall synthesis in fibers of Arabidopsis.
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.
Zhong
Ruiqin
R
Department of Plant Biology, University of Georgia, Athens, Georgia 30602, USA.
Demura
Taku
T
Ye
Zheng-Hua
ZH
D017360:Arabidopsis / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism*; D002482:Cellulose / Q000378:metabolism; D035264:Flowers / Q000166:cytology; D015870:Gene Expression; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D005799:Genes, Dominant; D008969:Molecular Sequence Data; D010802:Phylogeny; D019441:Plant Epidermis / Q000166:cytology; D018515:Plant Leaves / Q000166:cytology; D018547:Plant Stems / Q000166:cytology; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014934:Wood / Q000166:cytology / Q000378:metabolism*; D014990:Xylans / Q000378:metabolism
D029681:Arabidopsis Proteins; D012333:RNA, Messenger; C517318:SND1 protein, Arabidopsis; D014157:Transcription Factors; D014990:Xylans; D002482:Cellulose