DIFFERENTIAL GENE EXPRESSION ANALYSIS IN Vicia monantha UNDER DROUGHT STRESS CONDITIONS

Abstract

In Egypt and many countries of WANA (West Africa, North Africa), broad bean or faba bean (Vicia faba), is considered the most important food legume; consumed green or dried, fresh or canned, as well as for animal feed (Bond et al., 1985). Furthermore, feeding value of faba bean is high, and is considered in some areas to be superior to field peas or other legumes. It is one of the most important winter crops for human consumption in the Middle East (Duke, 1981). Different wild Vicia species from the Northwest coastal region of Egypt have been identified (Atlas of Legume Plant of the North West of Egypt, 1993). Vicia monantha is a member of the family Fabaceae, belonging to the genus Vicia. It is a wild plant species that is native to the Northern African region, mainly Algeria and Egypt. It is characterized by its obvious withstanding to severe environmental conditions. Such wild plants are considered as an excellent source of stress-related genes awaiting their isolation and identification. Abiotic stresses, such as drought, salinity, extreme temperatures, chemical toxicity and oxidative stress are serious threats to agriculture and result in the deterioration of the environment. Abiotic stress is the primary cause of crop loss worldwide, reducing average yields for most major crop plants by more than 50% (Boyer, 1982). Drought and salinity lead to inability of plants to acquire their water needs, resulting in loss of turgor and/or osmotic stress. At the molecular level, osmotic stress will trigger cascades of signals involving Ca++ and reactive oxygen molecules as primarily signals to activate pathways critical for plant survival under the stress conditions (Knight et al., 1997; Knight and Knight, 2001). At the cellular level, responses include metabolic adjustment to produce compatible solutes (Cherry, 1989), activation of transporters at the plasma and vacuolar membranes for ion sequestration or exclusion (Blumwald and Poole, 1985; Shi et al., 2000) and activation of enzymes involved in detoxification of free radicals (Mittova et al., 2002; Bor et al., 2003; Mittova et al., 2004; Badawi et al., 2004). At the whole plant-level, responses include closure of plant stomatal apparatus coupled with an inhibition of vegetative growth and increase in root growth (Maggio et al., 2003). Cloning and characterization of environmental stress-induced genes offer a chance for understanding the physiological responses of the plant cell to the environmental stresses. Moreover, it produces a source of genes for producing transgenic plants tolerant to abiotic stress. Differential display-polymerase chain reaction (DD-PCR) (Liang and Pardee, 1992) is a simple, powerful and sensitive method for the isolation of differentially expressed genes. It has been useful in characterizing and cloning of expressed sequence tags (EST) preferentially expressed in different tissues and/or under different conditions (Cushman and Bohnert, 2000; Martin-Laurent et al., 1997; Roux and Perrot-Rechenmann, 1997; Visioli et al., 1997; Deleu et al., 1999; Wei et al., 2000; Zhang et al., 2005; Yong et al., 2007; Yu et al., 2006; Perumal Venkatachalam et al., 2009). In this study, Vicia monantha was collected from Marsa Matrouh in the North coast of Egypt. In a previous study, the plant was subjected to salinity stress and a total of fifty three new EST was identified (Abd El-maksoud et al., 2009). In the current study, Vicia monantha was subjected to drought stress to isolate and characterize some of the key expressed sequence tags (ESTs) in response to drought stress using the differential - dis- play technique.