Salt-induced hydrogen peroxide is involved in modulation of antioxidant enzymes in cotton

Salt severely restricts cotton (Gossypium hirsutum) growth and production. The present study was undertaken to study the effect of salt-induced hydrogen peroxide (H2O2) on antioxidant enzymes in cotton. NaCl treatment or exogenous H2O2 was used to investigate the relationship between H2O2 content and levels of antioxidant enzymes including superoxide dismutase (SOD), ascorbate peroxidase (APX), peroxidase (POD), and catalase (CAT), as well as the transcriptional levels of corresponding genes. H2O2 content increased within 24 h following 200 mmol L-1 NaCl treatment. Both NaCl-induced and exogenous H2O2 increased the activity of antioxidant enzymes including APX and SOD and upregulated the transcriptional levels of GhcAPX1, GhFeSOD, and GhchlCSD. These increased activities and upregulated transcriptional levels were inhibited when the salt-induced H2O2 was scavenged by NAC. These results indicate that salt-induced H2O2 as a second signaling messenger modulates APX and SOD activities by regulating the transcription levels of corresponding genes, alleviating oxidative stress, and increasing salt tolerance in cotton.