Geoscience Reference
In-Depth Information
turn, regulates lateral root development under drought condi-
tions. Recent studies demonstrate the importance of auxin in
cold-stress-mediated plant gene expression and trafficking
(Shibasaki et al., 2009; Rahman, 2012). An auxin-resistant
mutant,
axr1-24,
shows more resistant salt concentrations, pro-
viding a link between auxin and salt stress (Tiryaki, 2007).
Abscisic acid
ABA, a terpenoid phytohormone, signal transduction pathway
leads to changes in plant gene expression in many ways, which
involves changes in the transcription, transcript processing,
chromatin modification and RNA stability (Guo et al., 2011).
There are many studies showing that ABA is a key regulatory
molecule in the control of gene expression in abiotic and biotic
stress such as drought, dehydration, cold, salinity as well as
pathogen interaction (Wasilewska et al., 2008). ABA has been
essential in transcriptional and post-transcription regulation of
stomata aperture, lateral root growth, seed germination, anti-
oxidant response and pathogen defence. Both biotic and abiotic
stress genes are induced and controlled by ABA-dependent and
ABA-independent pathways. Comparisons of transcriptomes
for
Arabidopsis
and rice exposed to ABA and various abiotic
stresses have shown changes affecting 5-10% of the genome;
more than half of these changes were common to drought, salin-
ity and ABA treatments (Shinozaki et al., 2003; Nakashima
et al., 2009). The ABA-regulated genes in
Arabidopsis
seed-
lings include slightly over 10% of the genome. This is 2-6
times as many genes are regulated by most of the other plant
hormones (Nemhauser et al., 2006; Nakashima et al., 2009).
ABA passes its signalling and controls gene expression using
a different set of receptors, such as, flowering time control
protein A (FCA), ChlH/ABA R (abscisic acid receptor)/CCH
(conditional chlorina)/GUN5 (genome uncoupled 5), GTGs
(GPCR-type G proteins) and PYR/PYL/RCARs (pyrabactin/
PYR-like/regulatory component of ABA receptors) (Guo et al.,
2011). The ABA-induced genes are enriched for those encod-
ing proteins involved in stress tolerance, such as dehydrins and
enzymes that detoxify reactive oxygen species (ROS), enzymes
of compatible solute metabolism, a variety of transporters, reg-
ulatory proteins such as transcription factors, protein kinases
and phosphatases and enzymes involved in phospholipid sig-
nalling. ABA-repressed gene products are enriched for proteins
associated with growth, including cell wall, ribosomal, plasma
membrane and chloroplast proteins.
NFYA5
(nuclear factor Y
A5),
OCP3
(overexpresser of cationic peroxidase 3),
MYB96
(MYB transcription factor 96),
FTA
(α-farnesyltransferase),
