Involvement of Dehydrins in the Response to Drought
The accumulation of dehydrins in plants is a common feature
of the response to drought (Close, 1997). Earlier studies indicated that the accumulation of certain dehydrin proteins in
seedlings was associated with drought tolerance in adult plants (Lopez et al.,
2003). Overproduction of a wheat dehydrin (DHN5) in Arabidopsis enhanced
the tolerance to osmotic stress. When compared to wild type plants, the
dehydrin-5 transgenic plants exhibited stronger growth under water deprivation
and more rapid recovery (Brini et al.,
2007).
Some genes coding for mainly low-molecular weight and some
alkaline YnSK-type dehydrins tend to be induced only by drought (Close et al.,
2000). Recent results have confirmed that, under water deprivation, white
clover synthesized an alternatively spliced Y2SK transcript, which
was absent after recovery of plant upon rehydration (Vaseva et al. 2011).
Two isoforms of YSK type dehydrin gene have been reported in
expression studies of Vitis riparia and Vitis vinifera (Xiao and
Nassuth 2006), and of winter wheat (Vaseva et al. 2010). Wheat WZY1-2 gene encodes a 262 amino acid
alkaline YSK2-type dehydrin with a predicted molecular weight of 28
kDa. It contains a serine-rich segment that can be phosphorylated and is
thought to participate in nuclear localisation (Close, 1997). Quantitative
differences in accumulation of WZY2 transcripts have been observed soon after
withholding water, in winter wheat cultivars with different drought tolerance
(Vaseva et al., 2010). The drought-tolerant variety showed a considerable
increase in WZY2 transcript levels, accompanied by the presence of a second,
high-density band, absent in the control samples. This alternatively spliced
WZY2 transcript occurred only in drought-stressed plants and its expression
levels were related to the drought-tolerance of the cultivars. The tolerant
variety tends to accumulate WZY2 alternatively spliced transcripts earlier than
the less tolerant ones. This makes WZY2 dehydrin a suitable candidate
for a molecular marker of drought tolerance.
Post Comment
No comments