Effect of nitric oxide treatment on antioxidant responses and psbA gene expression in two wheat cultivars during grain filling stage under drought stress and rewatering

The effect of sodium nitroprusside (SNP; nitric oxide donor) treatment on wheat plant (Triticum aestivum L.) under drought stress during grain filling stage was investigated. When two cultivars wheat plants, Yumai No. 949 and Shanmai No. 5, were drought stressed by PEG for 72 h and rewatered for 48 h, the affections of osmotic dehydration and rehydration on the antioxidant enzymes activities and psbA gene transcriptional abundance were compared. Relative water contents (RWC) decreased markedly after 72 h of PEG stress, along with an obvious decrease in chlorophyll content, increase in SOD, CAT and APX activities, and MDA content as well. Real-time quantitative polymerase chain amplification indicated that drought stress also remarkably inhibited the transcription of psbA gene in photosystem II (PSII). All of these responses could be restored by removing of stress and applying another 48 h of rewatering. The exogenous 0.2 mmol l(-1) SNP treatment could significantly alleviate the stress injury and accelerate the progress of recovery. Compared to Yumai No. 949, Shanmai No. 5 had less destroyed plasma membranes, higher RWC and chlorophyll contents, more psbA gene transcriptional abundance during water stress, and rapider recovery to control after rewatering, suggesting not only a better drought resistance but also a better recovery capability after a severe drought stress. The present results also suggested that the application of exogenous SNP could enhance the stress resistance of wheat plant during grain filling stage by increasing antioxidant enzymes activities, as well as protecting important gene transcription in PSII, which were to the benefit of functional recovery from drought stress.