ISOLATION AND CHARACTERIZATION OF Cab8 GENE FROM WILD Vicia cinera SPECIES

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