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 24h following 200mmol 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.