Salt-tolerance in Brassica juncea L. II. Salt-stress induced changes in polypeptide pattern of in vitro selected NaCl-tolerant plants

Summary

The effect of salt-stress was studied on SDS-PAGE pattern of polypeptides in seedling, leaf and siliqua tissues of four genetically stable lines (SR2P1-2, SR3P2-1, SR3P6-1 and SR3P6-2) of in vitro selected NaCl-tolerant plants, a non-selected somaclone (CP5-2) and parent variety Prakash of Brassica juncea L. Seedlings were raised in 0, 50, 100 and 150 meq/l NaCl solutions and plants were irrigated with nutrient solution with 0, 30, 60 & 90 meq/l NaCl. Salinity induced distinct genotype specific changes in polypeptide pattern of leaf and siliqua tissues, while it had no effect on the polypeptide pattern of seedlings, radicle or hypocotyl tissues in any of the lines. In leaves, at vegetative stage, a high molecular weight protein of 53.2 kD while disappered at 60 mM and higher NaCl level in cv. Prakash and SR3P2-1, it appeared in SR2P1-2 and CP5-2 only at these higher salt levels and in SR3P6 lines it was present irrespective of stress conditions. Differences were also observed for a 93.8 kD protein which appeared anew under stress in cv. Prakash, CP5-2 and SR2P1-2, while it was absent in SR-3 lines. Intensity of the 57.3 kD protein decreased in cv. Prakash, increased in SR-2 and CP-5 lines whereas remained unchanged in SR-3 lines under salt-stress. In siliquae, salt stress induced the expression of four new polypeptides (56.1–70.8 kD) at 60 mM NaCl in cv. Prakash, and at 30 mM in SR2P1-2, SR3P2-1 and SR3P6-1 lines, while these were present in CP5-2 and SR3P6-2 even in the absence of NaCl stress.