Physiological response and expression of genes involved in drought tolerance in tolerant and susceptible bread wheat cultivars

Water stress is one of the most important environmental factors that regulate plant growth and development, and limit production. Plants can respond and adapt to water stress by altering their cellular metabolism and invoking various defense mechanism. Manipulating the levels of antioxidative defence system may affect yield. Therefore, the aim of this study was to find out the relationship between gene expression of antioxidant enzymes and proline as an osmotic regulator in wheat cultivars under drought stress. For this purpose, a factorial experiment based on randomized complete block design was carried out with three replications. Treatments were two Iranian wheat cultivars (Pishtaz and Niknejad) and three levels of drought stress. Drought stress resulted in a reduction of Chl a, Chl b, total Chl and yield in both cultivars. This reduction was lower in tolerant cultivar Niknejad. Drought stress led to an enhancement in proline content, the activity of CAT (Catalase), APX (Ascorbate Peroxidase) and SOD (Superoxide Dismutase) enzymes. The tolerance of Niknejad cultivar under drought stress is associated with high chlorophyll (Chlorophyll), proline contents which is closely related to its enzymatic antioxidants activity (including CAT, APX and SOD). Our results showed that drought stress resulted in an increase in the gene expression of CAT, APX and SOD enzymes as well as enhanced the expression of gene for enzymes involved in the biosynthesis of proline (P5C5). Therefore, antioxidant enzymes and compatible osmolytes regulate plant yield mainly by modulating ROS with different mechanism.