NAC domain function and transcriptional control of a secondary cell wall master switch
Article first published online: 10 OCT 2011
© 2011 The Authors. The Plant Journal © 2011 Blackwell Publishing Ltd
The Plant Journal
Volume 68, Issue 6, pages 1104–1114, December 2011
How to Cite
Wang, H., Zhao, Q., Chen, F., Wang, M. and Dixon, R. A. (2011), NAC domain function and transcriptional control of a secondary cell wall master switch. The Plant Journal, 68: 1104–1114. doi: 10.1111/j.1365-313X.2011.04764.x
- Issue published online: 13 DEC 2011
- Article first published online: 10 OCT 2011
- Accepted manuscript online: 28 AUG 2011 06:20AM EST
- Received 15 August 2011; accepted 23 August 2011; published online 10 October 2011.
- NAC domain;
- transcription factor;
- secondary cell wall;
- transcriptional regulation;
NAC domain transcription factors act as master switches for secondary cell wall thickening, but how they exert their function and how their expression is regulated remains unclear. Here we identify a loss-of-function point mutation in the NST1 gene of Medicago truncatula. The nst1-3 mutant shows no lignification in interfascicular fibers, as previously seen in tnt1 transposon insertion alleles. However, the CA transversion, which causes a T94K mutation in the NST1 protein, leads to increased NST1 expression. Introduction of the same mutation into the Arabidopsis homolog SND1 causes both protein mislocalization and loss of target DNA binding, with a resultant inability to trans-activate downstream secondary wall synthesis genes. Furthermore, trans-activation assays show that the expression of SND1 operates under positive feedback control from itself, and SND1 was shown to bind directly to a conserved motif in its own promoter, located within a recently described 19-bp secondary wall NAC binding element. Three MYB transcription factors downstream of SND1, one of which is directly regulated by SND1, exert negative regulation on SND1 promoter activity. Our results identify a conserved amino acid critical for NST1/SND1 function, and show that the expression of the NAC master switch itself is under both positive (autoregulatory) and negative control.