Physiology and Molecular Biology of Stress ... - KHAM PHA MOI

Salt Stress
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Figure 5. Determinants of salt tolerance related to the main adaptive strategies (salt tolerance
and salt avoidance) of plants exposed to salinity
A survey of cell responses to salt stress identified a large number of genes
induced by salt. For example, 218 cDNA salt-inducible clones have been detected in
barley roots, of which 133 cDNA clones have homology to known proteins and 24 are
identified as genes for signal transduction (Ueda et al., 2002). A recent salt-treated
cDNA library of the halophyte Suaeda salsa can serve as a useful model for research
in salt-tolerant plants (Zhang et al., 2001). Differential display in mangrove Bruguiera
gymnorrhiza revealed nine transcripts up-regulated or induced by salt stress (Banzai et
al., 2002). The gene for NADP-malic enzyme in Aloe vera (AvME) was identified as a
gene induced by salt stress, whose expression was related to the degree of salt tolerance
(Sun et al., 2003). Five cDNAs isolated from wheat by modified differential display
were named WESR (wheat early salt-stress responding) and described as novel saltstress
responding genes (Nemoto et al., 1999). Mutational analysis of salt-sensitive
Arabidopsis to characterize salt-induced genes has been very useful in identifying as
well as their signaling pathways were determinants of salt tolerance (Zhu, 2000). The
coordinate mRNA accumulation induced in salt stress conditions has been reported in
different plants (Bohnert et al., 1995; Bray, 1997).
Alterations in transcript levels of many gene families in response to cation
stress revealed the existence of putative non-selective cation channels for NaCl treatment,
metal transporters for Ca 2+ starvation conditions, and the changes in mRNA
levels related to primary pumps, antiporters and aquaporins induced by stress (Maathuis
et al., 2003). As per the transcriptome changes in Arabidopsis in response to salt,
osmotic and cold stress, about 30% of the transcriptome is sensitive to regulation of
common stress conditions, and majority of changes were stimulus specific (Kreps et al.,
2002).