XND1, a member of the NAC domain family in Arabidopsis thaliana, negatively regulates lignocellulose synthesis and programmed cell death in xylem

Abstract

SummaryMembers of the large Arabidopsis NAC domain transcription factor family are regulators of meristem development, organ elongation and separation, and deposition of patterned secondary cell walls. XYLEM NAC DOMAIN 1 (XND1) is highly expressed in xylem. Changes observed for XND1 knockout plants compared with wild-type Arabidopsis thaliana included a reduction in both plant height and tracheary element length and an increase in metaxylem relative to protoxylem in roots of plants treated with the proteasome inhibitor MG132. Overexpression of XND1 resulted in extreme dwarfism associated with the absence of xylem vessels and little or no expression of tracheary element marker genes. In contrast, phloem marker-gene expression was not altered and phloem-type cells still formed. Transmission electron microscopy showed that parenchyma-like cells in the incipient xylem zone in hypocotyls of XND1 overexpressors lacked secondary wall thickenings and retained their cytoplasmic content. Considered together, these findings suggest that XND1 affects tracheary element growth through regulation of secondary wall synthesis and programmed cell death.

Natural Hypolignification Is Associated with Extensive Oligolignol Accumulation in Flax Stems

“…In this latter study, different MYB TF genes were expressed in flax stem tissues and seeds, although six MYB TF genes were also expressed in both tissues. We also observed that the flax orthologs of several genes encoding NAC factors, such as SND1, SND2, XND1, VNI2, and KNAT7, previously shown to be involved in the control of secondary cell wall formation and/or xylem vessel differentiation and forming part of a transcriptional control network, were also differentially regulated between inner and outer stem tissues (Zhao et al, 2008;Yamaguchi et al, 2010;Zhang et al, 2011;Zhao and Dixon, 2011).…”

Role of Plant Transcription Factors in Abiotic Stress Tolerance

“…ERD1 promoter analysis showed that TFs belonging to the NAC family and ZF-HD are important for the activation of the ERD1 (early responsive to dehydration stress 1) gene . XND1 is expressed in xylem and associated with stress, ABA response and leaf senescence in Arabidopsis (Zhao et al, 2008). In soybean 101 NAC domain containing proteins, identified as functionally nonredundant were involved in response to abiotic stresses and in cell death events whereas GmNAC2, GmNAC3 and GmNAC4 were strongly induced by osmotic stress (Pinheiro et al, 2009).…”

“…ONAC045 overexpressing rice plants showed enhanced tolerance to drought and salt treatments (Zheng et al, 2009). XND1overexpressing showed severe stunting, premature death, and repression of TE differentiation (Zhao et al, 2008). Hence NAC TFs play an indispensable role in physiological adaptation for successful plant propagation under abiotic stress conditions.…”

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]. …”