Chemistry Reference
In-Depth Information
cells, it has been shown that the strong induction of Stress Responsive-NAC1 (SNAC1) gene
expression by drought also affect stomatal closure (Hu et al. 2006).
2.5.2. Flooding stress
Flooding and submergence are two stresses lead to anoxic conditions in the root system.
Under this stress condition, both anoxia and hypoxia are defined by O
2
shortage. But diverse
plants have their own way to adjust to it. Some lowland rice cultivars, such as FR13A, can
survive submergence by suppressing shoot elongation. At the molecular level,
Submergence-1 (Sub1), which is derived from FR13A, is a major quantitative trait locus
contributing to great submergence tolerance (Xu et al. 2006). And three sequentially arrayed
genes (designated
Sub1A
,
Sub1B
, and
Sub1C
) has been identified.
Sub1A
has been proved to
encode an ERF domain-containing TF associated with the induction of low oxygen escape
syndrome (LOES) (Bailey-Serres and Voesenek, 2008 ).
In plants, different cell types exhibit a conserved response to low oxygen levels at the
molecular level (Mustroph et al. 2010). This response includes the induction of genes after 30
min under hypoxia, whose expression is maintained for several hours (Klok et al. 2002; van
Dongen et al. 2009). The increased transcript levels of these genes are further accompanied
by active combination between mRNAs and polysomes reflecting promoted translation
process (Branco-Price et al. 2008). Unfortunately, in plants the mechanism by which oxygen
is perceived has not been clarified. But researches on hypoxia-responsive TFs can help us a
lot to investigate the regulation of the hypoxic response. Usually these TFs are detected in
families like MYB, NACs [Arabidopsis Transcription Activation Factor (ATAF) and Cup-
shaped Cotyledons (CUC)], Plant Homeodomain (PHD) and ERF families (Hoeren et al.
1998; Christianson et al. 2009; Licausi et al. 2010b). And on the other hand, Microarray data
in Arabidopsis and rice research find us several transcription factors whose expression
increases induced by oxygen deprivation, such as heat shock factors, MADS-box proteins,
and WRKY factors (Lasanthi-Kudahettige et al., 2007). Recently Licausi et al. (2010a) have
identified TFs that are differentially expressed under hypoxic conditions. The results
indicate members of the AP2 ⁄ ERF-type family are the most common upregulated TFs,
followed by Zinc-finger and basic helix-loop-helix (bHLH-type) TFs. TFs belonging to the
bHLH family also appear in the downregulated part, together with members from the bZIP
and MYB families.
On the other hand, by
silico
experiments and trans-activation assays it has been confirmed
that five hypoxia-induced TFs (At4g29190; LBD41, At3g02550; HRE1, At1g72360; At1g69570;
At5g66980) from different TF families [Zinc Finger, Ligand Binding Domain (LBD)/Lateral
Organ Boundary Domain, ERF, DNA binding with one finger (DOF), ARF] respectively
showed the ability to regulate the expression of hypoxia responsive genes (Licausi et al.
2010b). Other evidence relating to TFs and adaptive response to low oxygen will refer to
redox-sensitive TFs. ZAT12, a putative zinc finger-containing TF, is identified as an
important link in the oxidative stress response signalling network in Arabidopsis (Rizhsky
et al. 2004), for its transcript levels were remarkably mounted up in response to hypoxia and
anoxia in several independent analyses (Branco-Price et al. 2005).
