Overexpression of an expansin-like gene, GhEXLB2 enhanced drought tolerance in cotton.

Expansins are nonenzymatic cell wall proteins that play significant role in plant development as well as stress responses. Hereby, an expansin-like gene, GhEXLB2 was isolated from a cotton (Gossypium hirsutum L.) protoplast with suppression subtractive hybridization to characterize and study its responses against abiotic stresses. GhEXLB2 is the cell-wall localized protein. The expression of GhEXLB2 level was significantly high under polyethylene glycol and salt treatments. GhEXLB2 was further characterized in vitro by cloning and transformation into cotton. Cotton plants overexpressing GhEXLB2 showed enhanced drought tolerance at germination, seedling and flowering stages. After polyethylene glycol (PEG) treatment at germination stage, the length of main root and hypocotyl of overexpressing lines was significantly longer than YZ1 (wild type) and RNAi lines. In addition, H2O2 and malondialdehyde (MDA) contents were lower, while superoxide dismutase (SOD) and peroxidase (POD) activity was detected higher in overexpressing seedlings. On the other hand, higher SOD and POD activity was detected in overexpressing lines than WT plants in soil. In addition, water use efficiency (WUE), soluble sugar, and chlorophyll contents were also significantly greater in overexpressing plants. The present study revealed that GhEXLB2 play crucial role in enhancing drought resistivity in cotton.