Ultrastructural, metabolic and proteomic changes in leaves of upland cotton in response to cadmium stress

Present study explores physiological, biochemical and proteomic changes in leaves of upland cotton (ZMS-49) using 500 μM cadmium (Cd) along with control. Leaves' biomass and chlorophyll pigments decreased at 500 μM Cd. Cd contents in roots were higher than leaves. Levels of ROS (O2 and H2O2) both in vivo and in vitro and MDA contents were significantly increased. Chlorophyll parameters (F0, Fm, Fm′ and Fv/Fm), total soluble protein contents and APX showed a decline at 500 μM Cd. SOD, CAT and POD and GR activities significantly enhanced. Less ultrastructural alterations in leaves under Cd stress could be observed. Scanning micrographs at 500 μM Cd possessed less number of stomata as well as near absence of closed stomata. Cd could be located in cell wall, vacuoles and intracellular spaces. Important upregulated proteins were methionine synthase, ribulose 1,5-bisphosphate carboxylase, apoplastic anionic guaiacol peroxidase, glyceraldehydes-3-phosphate dehydrogenase (chloroplastic isoform) and ATP synthase D chain, (mitochondrial). Important downregulated proteins were seed storage proteins (vicilin and legumin), molecular chaperones (hsp70, chaperonin-60 alpha subunit; putative protein disulfide isomerase), ATP-dependent Clp protease, ribulose-1,5-bisphophate carboxylase/oxygenase large subunit. Increase in the activities of ROS-scavenging enzymes, less ultrastructural modification, Cd-deposition in dead parts of cells as well as active regulation of different proteins showed Cd-resistant nature of ZMS-49.