Some Biological Aspects and Proline Metabolism Genes as Influenced by Polyethylene Glycol and Salicylic Aacid in Two Wheat Cultivars

The aim of this work was to study the response of two wheat cultivars with different drought tolerance to PEG (-0.4 Mpa) and SA (0.5 mM). Data of seed germination and seedling growth indicated that Misr-2 cultivar was more drought tolerant than Gemmeiza-12. Under non- stress conditions, Misr-2 had higher values of pigments, soluble sugars (Glu, Fru and Suc) and activities of antioxidant enzymes (CAT, APOX, GPOX and SOD) but lower values of proline than those of Gemmeiza-12. The cultivar with a higher proline content (Gemmeiza-12) compared to the other cultivar had a higher expression of proline synthesizing gene (P5CS) but lower expression of proline degrading genes (PDH and P5CDH). Under drought conditions, the drought-sensitive (Gemmeiza-12) needed more osmoregulators and antioxidants than drought-tolerant cultivar (Misr-2) to minimize the negative effects of water and associated oxidative stresses. Therefore, soluble sugars, proline content and anti-oxidation enzymes were higher in Gemmeiza-12 than Misr-2. Also, under drought stress, up-regulation of P5CS and down-regulation of PDH and P5CDH in Gemmeiza-12 were higher than Misr-2. While treatment of the stressed plants with SA up-regulated P5CS gene in both cultivars, down-regulation of PDH and P5CDH in Gemmeiza-12 was clearer than Misr-2.