Evaluating expression of genes involved in proline synthesis pathway in mutant wheat T65-58-8 under drought stress

Drought stress is an important yield-restricting factor in arid and semi-arid areas. Drought tolerance is a multigenic character and it occurs in various stages of growth. Since the mutagenesis is a fast and safe method, it can be used to diversify genetic contents of plant with the purpose of enhancing quantitative and qualitative traits. In this research, expression pattern of some genes involved in ABA-independent pathway in Tabasi Cultivar (drought sensitive) and mutant line T65-58-8 (drought tolerant, treated with 250 gray gamma radiation) were evaluated under drought stress conditions at maturity stage. In order to study the expression of genes involved in production of proline (P5CS, P5CR and P5CDH) and measuring its amount under drought stress and re-irrigation condition, seeds of two genotypes mentioned above were cultured in 24 cm pots. At the anthesis stage, irrigation was stopped until wilting symptoms appeared, then sampling from flag leaf was done at appropriate intervals (two, three, four, five and six days after irrigation stoppage) and also 12 hours, three, four and five days after re-watering. The control treatment underwent sampling simultaneously. The study was conducted as a factorial experiment based on completely randomized design with two biological replicates. The results demonstrated that the increment of drought stress led to higher expression of P5CS gene in Tabasi cultivar compared to the mutant line, while P5CR gene was more expressed in the latter. The expression of P5CDH in mutant line decreased, while Tabasi cultivar showed an increase in this regard. After re-irrigation, the expression of P5CS and P5CR in both genotypes decreased compared to the control, whereas P5CDH gene was expressed less and more in mutant line and Tabasi cultivar, respectively. Also, the results indicated that proline concentration in the mutant line increases more than Tabasi cultivar under drought stress, while it decreases in both genotypes as a result of re-irrigation. In general, mutant line T-65-58-8 adopts better remedial responses for expression of genes involved in proline production compared to Tabasi cultivar so as to remain undamaged, and it is probable that the osmolyte pathway underwent some changes as result of exposure to gamma rays.