Abstract:
Drought stress is a limiting factor to
the agricultural productivity in tropical, semi-arid and arid regions. More than
95% of Egypt’s land is desert, while less
than 3% is confined to farming and agriculture. Drought stress causes cellular
water deficits, which results in the loss of
turgor, change in cell volume, change in
membrane integrity, concentration of solutes, denaturation of proteins and several
physiological and molecular components
(Bartels and Souer, 2003; Griffiths and
Parry, 2002; Lawlor and Cornic, 2002;
Parry et al., 2002; Raymond and Smirnoff,
2002). Under such severe conditions, cells
need to induce gene(s) producing some
products that may act to sustain the cellular functions through osmotic adjustments
and cellular structure protection (Bray,
2002).
High drought conditions and high
light intensity from the sun is very damaging to plants subjected to these conditions.
The morphology, molecular and biochemical characteristics of the plant structure contribute to maximizing the photon
capture and their use in CO2 fixation
(Larcher, 1995).
Photooxidative stress was known
to be the cause of the oxidative stress, but
it has been proven that it also results from
drought and salinity stresses. Oxidative
stress is characterized by the accumulation
of harmful reactive oxygen species (ROS)
in plant tissues, and it is one of the most
deleterious stresses. Most of the environmental stresses result in the overproduction of ROS, which consequently causes
an oxidative stress. The reaction of ROS
with lipids and proteins results in the fast
accumulation of toxic products, which
brings severe damage to the plants. One of
these toxic products is lipid peroxide
which causes cellular damage (Chia et al.,
1984; Dhindsa et al., 1981).
Cab gene family is a Light Harvesting Complex II type I (LHCI), which
is responsible for capturing, transporting
and distributing the excitation energy to
photosystems that are closely related, organizing the photosynthetic system by
keeping the tight compensation of the thylakoid membranes and protecting the plant
against any damage resulting from high
light intensity- photooxidative stress.
Cab6A, B (LHCI type I); Cab7, LHCZ-15
(LHCI type II); Cab8 (LHCI type III) and
