الفهرس 
Isolation, characterization and evaluation of physiological roles of genes related to abiotic stress
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Abstract
Salt stress is one of the major environmental stresses in agriculture and affects crop productivity and quality worldwide. In the present study, two genes encoding Na + / H + antiporters in addition to one gene from the HKT family were isolated from cyanobacterial strain synechocystis sp. PCC 6803, cloned and sequenced. These genes, namely ktrB, nhaS2 and nhaS4 were further cloned into the pYES2 vector for expression in saccharomyces cerevisiae. Transgenic yeast cells were examined for their ability to survive under salt - stress conditions and their growth response to increasing levels of NaCl (0, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2 and 2.3M) for 7days, was measured at OD600nm. The results revealed significant differences in growth between the transgenic yeast and control. The salt concentration of 1.8M NaCl was critical in determining the ability of yeast to tolerate salt stress. At this concentration, the mean growth values for the transgenic yeast harboring the genes ktr B , nhaS2 or nhaS4 were 1.2170cA, 1.2250cA and 1.2180cA, respectively, compared to 0.2620cB for the control. Moreover, increasing the salt concentration to 1.9 M NaCl, inhibited the growth of the control cells significantly