enrichment and expression of some carbohydrate related genes in indica rice seedlings under salt stress

Salt-affected soil is one of the most important abiotic stresses, leading to reduce rice productivity in many regions of the world. The objective of this investigation was to determine the Na, soluble sugar and starch contents and expression of some starch-related genes in two genotypes, Pokkali (salt tolerant) and IR29 (salt sensitive), grown under 200 mM NaCl. Three-week-old rice seedlings cvs. Pokkali and IR29 were treated with 0 or 200 mM NaCl subsequently Na, starch content, soluble sugar and growth characters were evaluated. The Na concentration in salt-stressed seedlings cv. IR29 was reached following leaf sheath>leaf blade>root tissues. Na accumulation in leaf blade and leaf sheath was positively related to soluble sugar enrichment (r>0.68). In starch biosynthesis, OsAGPS2b mRNA expression in leaf blade of rice seedlings cv. Pokkali was up-regulated for 66%, when exposed to 200 mM NaCl for 48h, leading to starch accumulation. Soluble starch content in salt-stressed seedlings was peaked to 68.84 g g FW in the leaf blade of cv. Pokkali and 165.83 g g FW in leaf sheath of cv. IR29 which was confirmed by iodine dye staining. In cv. Pokkali, soluble starch in the leaf blade of salt-stressed seedlings was enhanced and correlated with Na gathering CoroNa green emission. Growth performances of indica rice cv. IR29 seedlings were significantly declined when subjected to salt stress for 4 d. Na absorption by root tissue was greater in IR29 than that in Pokkali. The starch concentration in salt-stressed seedlings of cv. Pokkali was the maximum to 68.8 g g FW in the leaf blade, and it related to up-regulated levels of OsAGPS2b mRNA and OsGPL1. The study concludes that the regulation of carbohydrate metabolism in salt tolerant cultivar of rice may play a key role as a major salt defense mechanism when seedlings subjected to 200 mM NaCl.