Browsing by Author "M. K. NADA, A."

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CLONING OF TWO DEHYDRIN GENES FROM THE HALOPHYTES OF THE EGYPTIAN NORTHWEST COASTAL REGION
(Egyptian Journal of Genetics And Cytology, 2009) M. K. NADA, A.; M. ABDELHALIM, H.; FAHHAD, A.
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
ISOLATION AND CHARACTERIZATION OF Cab8 GENE FROM WILD Vicia cinera SPECIES
(Egypt. J. Genet. Cytol, 2009) M ABOU ALI, RANIA; M. EL-HEFNAWY, MENNATALLAH; M. K. NADA, A.
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