The interaction of reactive oxygen species and antioxidants at the metabolic interface in salicylic acid-induced adventitious root formation in mung bean [Vigna radiata (L.) R. Wilczek]

Implications of the role of antioxidant buffering in reactive oxygen species (ROS)-antioxidant interactions and associated redox regulation during adventitious root formation (ARF) were assessed in redox-manipulated salicylic acid (SA)-treated hypocotyl explants of mung bean [Vigna radiata (L.) R. Wilczek]. Application of pro-oxidant H2O2 (500 μM) followed by SA (600 μM) was shown to stimulate ARF, whereas treatments combining 600 μM SA and 10 × 10-4 M DPI (diphenyleneiodonium, an inhibitor of NADPH-oxidase) and 600 μM and SA 10 × 10-4 M (dimethylthiourea, a free radical scavenger) were found to prevent ARF. The redox status of the experimental explants monitored under such treatment conditions (in terms of accumulation of pro-oxidants, in situ localization of O2- and H2O2, radical scavenging property and total thiol content) revealed significant changes in ROS-antioxidant interactions at the metabolic interface, causing alterations in the pattern of ARF. Further, the assessment of activities and transcript abundance of the enzymes of the H2O2 turnover pathway (mainly the ascorbate-glutathione system) supported the transcriptional regulation of genes such as vrrboh, vrAPX, vrGR, vrSOD, and vrCAT and the activities of the relevant enzymes necessary for the generation of endogenous redox cues during ARF. The present work provides an inventory in support of the importance of antioxidant buffering associated with redox regulation for the origin of the metabolic redox cue (redox signal) necessary for SA-induced ARF in mung bean.