Protein electrophoretic profiles and physiochemical indicators of salinity tolerance in sorghum (<i>Sorghum bicolor</i> L.)

Abstract

The present study was conducted to quantify the response of chlorophyll, protein concentration and electrophoretic patterns of leaf and root soluble proteins to increasing salinity in the rooting medium of three varieties (Payam, Kimia and Jambo) of sorghum (Sorghum bicolor L.) and to evaluate the usefulness of these parameters in identifying salt-resistant varieties. This work was carried out with five concentrations of salinity (0, 50, 100, 150 and 200 mM NaCl) and two sampling time points (sampling after 15 and 30 days salt treatment) using a split split plot design with randomized complete block layout. With increasing salinity, the K+ concentration was found to decrease and the amount of Na+ and Na+/K+ increase significantly (P≤0.05) in roots and shoots. Chlorophyll a, b, total chlorophyll concentration and leaf and root soluble protein contents decreased with increasing salinity. The electrophoretic pattern of soluble proteins of cv. Jambo showed that after 15 days NaCl (200 mM) and 30 days NaCl (100 and 150 mM) treatment, a new polypeptide of molecular weight 50 kDa was expressed. The expression of this polypeptide might have been due to the plant adapting to NaCl via expression of a stress-resistant gene. This polypeptide was synthesized under salt stress and is suggested as a marker protein for salt adaptation.

Keywords: Chlorophyll, electrophoretic patterns, soluble proteins, salinity, sorghum