Abstract:
Throughout their life cycle, plants are
subjected to many adverse environmental stresses such as drought, high
temperatures, etc. that dramatically affect
plant survival and reduce productivity. To
cope with such stresses, plants produce
several stress-induced proteins that play a
definite role in protecting plants during
such severe conditions (Muthalif and
Rowland, 1994).
The late embryonic stage represents one of the abiotic stress conditions
where the seed starts to lose water content
during desiccation. Several molecules
have been found to play vital roles in seed
development and are thought to help in
saving the embryos during desiccation.
These include sugars (Koster and Leopold, 1988; Chen and Burris, 1990) and
proteins, among which are the lateembryogenesis abundant proteins (LEA)
(Blackman et al., 1995; Dure, 1993;
Close, 1996; Ingram and Bartels, 1996).
LEA proteins were found in the seeds of
several plants and in vegetative organs,
especially under abiotic stress conditions
(Thomashow, 1999; Hundertmark and
Hincha, 2008). According to amino acid
sequence homology, LEA proteins have
been separated into different groups
(Hundertmark and Hincha, 2008). From
these groups the LEA D11 family (LEA
type 2 proteins), also known as Dehydrins
(Close, 1997), have been estimated to
comprise up to 4% of the total seed protein. (Wise and Tunnacliffe, 2004).
Expression of the Dehydrin proteins have been found to be associated
with the protection of various types of
plant cells from osmotic stresses, such as
those caused by desiccation, salt, and low
temperatures (Skriver and Mundy, 1990;
Close, 1996; Ingram and Bartels, 1996;
Allagulova et al., 2006). Hyper-osmotic
conditions and low temperatures cause
cellular dehydration, resulting in the reduction of cytosolic volumes and the alteration of cellular mechanisms. Toward
survival, plants accumulate Dehydrin proteins during these conditions in the dehydrating plant tissue, (Abba et al., 2006).
Several studies revealed that Dehydrins are widely distributed in the plant
kingdom (Abba et al., 2006), in brown
algae (Li et al., 1998), in lichen Selaginella lepidophylla (Close, 1997) and
in cyanobacterium (Close et al., 1993).
A number of Dehydrin proteins
have been isolated and studied; the
physiochemical and/or structural mecha
