Biology Reference
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inflorescence stem and that integrate the metabolic flux through the lignin,
flavonoid and polysaccharide pathways (
Bhargava et al.,2010
). The excess
production of PAP1 by activation tagging might saturate the recruitment of
such a protein partner leading to opposite effects.
IV. THE NAC-MEDIATED REGULATION OF THE SW
In Arabidopsis, some members of the NAC (NAM, ATAF1/2 and CUC2)
domain TF family are known as master switches of SW development. They
include the NAC SECONDARY WALL THICKENING PROMOTING
FACTORS (NST1, 2, 3) specific for fibres, and the VASCULAR-RELATED
NAC-DOMAIN (VND1, 2, 3, 4, 5, 6, 7) specific for vascular vessels (
Kubo
et al., 2005; Yamaguchi, 2010; Yamaguchi et al., 2008, 2010a
). Both NSTs and
VNDs belong to the same NAC subfamily (
Yamaguchi, 2010
) and function as
transcriptional activators.
The nomenclature of these genes is author-dependent and the same gene can
have several names leading to some confusion. For instance, the gene NST3
(At1g32770) has two other names: SND1 for Secondary wall-associated NAC
Domain Protein1 (
Zhong et al.,2006
) and also ANAC012 (
Ko et al.,2007
). In
this manuscript, we will refer to it as SND1, which is the most commonly used
nomenclature, and in some cases we will refer to it by the double nomenclature
NST3/SND1. A similar situation exists for P. trichocarpa where different
names are also given by different authors: PtrWND (for wood-associated
NAC domain TF) by
Zhong and Ye (2010)
and PtVNS (VND-, NST-/SND-,
SMB-related proteins) by
Ohtani et al. (2011)
.
A. NAC
S
REGULATING SWS IN FIBRES
In Arabidopsis, NST2 is expressed in anther endothecium (
Mitsuda et al.,
2005
), NST3/SND1 in fibre cells of inflorescence stems, in hypocotyls and in
siliques (
Ko et al., 2007; Mitsuda and Ohme-Takagi, 2008; Mitsuda et al.,
2007; Zhong et al., 2006
), and NST1 expression overlaps with both NST2
and NST3/SND1 gene expression patterns (
Mitsuda and Ohme-Takagi,
2008; Mitsuda et al., 2007
). NST1 and NST2 act redundantly to regulate
the SW thickening in anther walls (
Mitsuda et al., 2005
). Indeed, secondary
wall thickening and lignification are known to play important roles in the
dehiscence of anthers and the shattering of silique pods. Both NST1 and
NST2 induce ectopic secondary wall thickenings in various tissues when
expressed ectopically (
Mitsuda et al., 2005
). NST1 and NST3/SND1 redun-
dantly regulate SW thickening in interfascicular fibres of inflorescence stems
