Investigation of relative expression of candidate genes related to salinity tolerance at seedling stage of rice using real-time PCR

Rice is a food source for more than half of the world's population and it is important as a model plant for monocots, and also its growth and yield is strongly affected by salinity stress, hence comprehensive research is essential for the development of salt tolerant varieties. In the present study, the expression pattern of several new genes involved in salt tolerance of rice was investigated by Real-Time PCR in sensitive (ARC6578 and Shoemed) and tolerant (Bombilla) rice cultivars.

RNA samples were extracted from 20-day-old seedlings treated with NaCl (100 mM) at three times of 24, 48 and 72 h after salt stress. Gene expression analysis was performed on 7 candidate genes (including SOD, CatA, 14-3-3 like protein GF14, Proxidase BP1 precursor, Zinc ion binding protein and Plasma Membrane H+-ATPase, OsSIPK) using real-time PCR. The Actin gene was used as the reference gene.       

The expression of OsSIPK in tolerant cultivar was increased 24 and 48 h after salt stress and was decreased 72 h after stress, while the expression of Zinc ion binding protein was decreased in all cultivars at all times after stress. The expression of PM H+-ATPase at early times after stress in both tolerant and sensitive cultivars was increased but it decreased after 72 h in sensitive cultivar and increased in tolerant cultivar. The expression of 14-3-3 like protein GF14-6 was highly increased at 48 h after stress but it was decreased after 72 h in sensitive cultivars and increased in tolerant cultivar. The expression of Peroxidase BP1 precursor was increased up to 40 times at 72 h after stress in tolerant cultivar. The expression of CatA was significantly increased at 72 h after stress only in tolerant cultivar. The expression of SOD didn't show a special time pattern, although its expression in tolerant cultivar was higher than that in sensitive cultivar at 72 h after stress.

Some genes in this research did function in general response of the rice plant to salt stress via scavenging the reactive oxygen species (ROS) (such as SOD and CatA). In another hand, a time-cultivar dependent relationship between salt tolerance and expression level of other studied genes (such as OsSIPK, PM H+-ATPase, 14-3-3 like protein GF14-6 and Peroxidase BP1) could be recognized.