Expression of Genes Involved in Fructan Metabolism in wheat Stem under Water Deficit Stress

Water deficient stress is one of the major limiting factors of wheat production in arid and semiarid areas of the world such as Iran. Under water deficient stress photosynthesis is limited and remobilization of assimilates stored in stems is more important to grain filling. In order to molecular analysis of fructan remobilization in wheat stem (penultimate) under terminal water deficit stress, T-65-7-1 mutant line (M7, the results of gamma irradiation) along with its wild type (cv. Tabasi), in terms of relative gene expression involved in biosynthesis and hydrolysis of fructan and transport of sucrose were studied. Water deficit treatment (30-40% field capacity) initiated at full heading stage (Zadoks 60) and sampling was conducted at two stages (7 and 21 days post anthesis). In the T-65-7-1 mutant line, a significant increase was observed in expression levels of genes involved in fructan biosynthesis (1-SST and 6-SFT), fructan biosynthesis (6-FEH) as well as sucrose transport (SUT1 and SUT2) compared to the wild type (cv. Tabasi). This event is due to more remobilization in T-65-7-1 mutant compared to the wild type. In T-65-7-1 mutant, during early grain filling period, 1-SST and 6-SFT produces more storage of fructan in the stem. Also, during rapid grain filling stage, 6-FEH produces more sucrose and finally, SUT1 and SUT2 transports more sucrose from stem to grain. In wheat breeding programs, 1-SST, 6-SFT, 6-FEH, SUT1 and SUT2 can be used as indicators for selecting genotypes with high fructan content and more remobilization.