Hydrogen peroxide acts as a signal molecule in the adventitious root formation of mung bean seedlings

Hydrogen peroxide (H2O2), an active oxygen species, is widely generated in many biological systems and mediates various physiological and biochemical processes in plants. in this study we demonstrated that the exogenous H2O2 was able to promote the formation and development of adventitious roots in mung bean seedlings. Treatments with 1-100 mM H2O2 for 8-18 h significantly induced the formation and development of adventitious roots. Catalase (CAT) and ascorbic acid, which are H2O2 scavengers or inhibitors, eliminated the adventitious root-promoting effects of exogenous H2O2 center dot H2O2 may have a downstream signaling function in the auxin signaling pathway and be involved in auxin-induced adventitious root formation. 2,3,5-Triiodobenzoic acid (TIBA), an inhibitor of auxin polar transport, strongly inhibited adventitious rooting of mung bean seedlings: however, the inhibiting effects of TIBA on adventitious rooting can be partially reversed by the exogenous IBA or H2O2. Diphenylene iodonium (DPI) strongly inhibits the activity of NADPH oxidase, which is one of the main sources of H2O2 formation in plant cells. DPI treatment strongly inhibited the formation of adventitious roots in mung bean, but the inhibitory effects of DPI on rooting can be partially reversed by the exogenous H2O2 or IBA. This indicates that the formation of adventitious roots was blocked once the generation of H2O2 through NADPH oxidase was inhibited, and H2O2 mediated the IBA-induced adventitious root formation. Furthermore, a rapid increase in the endogenous level of H2O2 was detected during incubation with water 12-36 h after the primary root removal in mung bean seedlings. Three hours after the primary root removal, the generation of endogenous H2O2 was markedly induced in IBA-treated seedlings in comparison with water-treated seedlings. This implies that IBA induced overproduction of H2O2 in mung bean seedlings, and that IBA promoted adventitious root formation via a pathway involving H2O2. Results obtained suggest that H2O2 may function as a signaling molecule involved in the formation and development of adventitious roots in mung bean seedlings. (C) 2008 Elsevier B.V. All rights reserved.