Proline Accumulation and Related Genes in Wheat Leaves under Salinity Stress

This study was carried out to evaluate the effects of salinity stress (16 dS m1) on proline accumulation and expression pattern of three genes involved in the proline synthesis (P5CS, P5CR) and degradation (PDH) in the fourth and the flag leaves. The experimental treatments consisted of two levels of salinity stress including 1.6 (control) and 16 dS m1 and three wheat cultivars, namely, Hirmand and Chamran (as tolerant cultivars) and Atrak (as sensitive). These were arranged as factorial based on a Completely Randomized Design with three replications. There was an increase in Na^+ concentration and decrease in K^+ concentration in salinity stress compared to the control condition in the fourth and the flag leaves of all cultivars. However, the tolerant cultivars showed lower level of Na+ concentration and higher level of K^+ concentration and K^+/ Na^+ ratio. Seemingly, the increase in proline accumulation was due to P5CS, P5CR upregulation and PDH downregulation. On the other hand, the higher proline degradation in the fourth leaf of the tolerant cultivars was probably due to the provision of a source for energy or nitrogen, which helped to enhance the yield of these cultivars under salinity stress.