Molecular analysis of hypersensitive reaction and senescence process in wheat leaves

In this study the expression of genes encoding some antioxidant enzymes in leaf senescence process and hypersensitive response in two wheat genotypes (Tajan and 10# line) was evaluated. Leaf samples were collected at 4 senescence stages: s1: starting yellowish of bottom leaves، 2:20% of average leaf yellowish، s3:40% of average leaf yellowish and s4:60% of average leaf yellowish and green leaf as well as leaf sampling in hypersensitivity (HR) followed by inoculation of septoria tritici blotch pathogen (Mycosharella graminicola). Gene expression analysis (CAT: catalase، MT: metallothioneine، GC: glothamine cyntatase) carried out by using real time PCR technique. The results showed TBARM amount (cellular oxidative level) was at the highest level at HR and s4 senescence stage. In contrast، chlorophyll content declined at HR and during senescence stages from s1 to 4 in compare with green leaf. The gene expression ratio of CAT and MT increased steadily during senescence and it was at the highest level at s4 for both genes. Whether، the expression levels for these genes were different at HR. Indeed CAT and MT showed same activity as s2 and s4 respectively. GC transcript levels increased up to s3 and then dropped sharply. At HR، GC activity was same as s2 stage.