Role of reactive oxygen species and ethylene as signaling molecules for the wound-induced biosynthesis of glucosinolates in broccoli ( Brassica oleracea L. Italica)
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2018 International Society for Horticultural Science. All rights reserved. Broccoli is an excellent source of glucosinolates (GS), which are bioactive compounds with chemopreventive properties. Therefore, it is relevant to find postharvest treatments that allow their accumulation. Broccoli under wounding stress accumulates GS. Stress signaling molecules such as reactive oxygen species (ROS) and ethylene (ET) are involved on the activation of defense genes. However, their specific role in GS synthesis as a response to wounding stress has not been elucidated. In the present project, diphenyleneiodonium (DPI, inhibitor of ROS biosynthesis) and 1-methylciclopropane (1-MCP, blocker of ethylene action) were added to wounded broccoli (florets cut into four even pieces), in order to determine the role and interaction of ROS and ET signaling molecules in the wound-induced biosynthesis of GS. Wounded broccoli florets with and without ROS and ET inhibitors were incubated for 24 h at 20C, and their GS profiles were determined by HPLC-DAD-ESI-MSn. Results indicated that wounding stress induced an increase of ~490% in total GS. ROS and ET showed to have a different role in the biosynthesis of individual GS. For instance, wounding stress induced the synthesis of 4-hidroxyglucobrassicin and neoglucobrassicin about ~4200 and ~1300%, respectively. However, blocking ET reduced neoglucobrassicin increment to ~280%. Meanwhile ROS inhibition resulted on the complete repression of 4-hidroxyglucobrassicin, glucobrassicin and neoglucobrassicin biosynthesis. In conclusion, results showed that ROS play a crucial role in the wound-induced biosynthesis of indole GS, whereas ET is specially involved on inducing neoglucobrassicin and 4-hidroxy-glucobrassin accumulation.
