Studying the effect of salinity and osmotic stresses on the biochemical reaction of sesame (Sesamum indicum L.) and bioinformatics evaluation of the SOD gene family

Sesame (Sesamum indicum L.) is one of the most important oil seed crops used by humans and accounts for a remarkable portion of global high-quality oil production. In this study, the effect of the same osmotic pressure provided by NaCl (salt stress) and by PEG600 (osmotic stress) on the biochemical reaction of sesame was evaluated. Results showed that the activity patterns of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and peroxidase (POD) enzymes were similarly affected by these stresses. Means comparison results indicated that the activity of POD was similar in both root and shoot tissues under both conditions. Also, the activity of SOD and APX enzymes was higher under salinity than under osmotic stress in both sesame tissues. The CAT activity was higher under salinity as compared with the osmotic stress in sesame roots, while in shoots, its activity was higher under osmotic stress compared with salinity. No significant difference was observed in Malondialdehyde accumulation in roots, while it reached its maximum under salinity in shoots. The bioinformatics analysis of the SiSOD gene family revealed that it can be classified into three clusters and into two major groups. Genes belonging to the first cluster have the CU/ZN-SOD domain, while genes belonging to the second cluster have the Mn/Fe-SOD domain. In conclusion, our findings indicated that sesame was more affected by salinity than osmotic stress, which could be due to both osmotic and ionic pressure created by NaCl. Therefore, the response of sesame defense systems to both studied stresses can be relatively different.