Hydrogen Peroxide Is a Second Messenger in the Salicylic Acid-Triggered Adventitious Rooting Process in Mung Bean Seedlings

Wei Yang,Xiaoling Ma,Changhua Zhu,Lijun Gan,Guijun Li,Kai Xia,Denny Ng,Keqiang Wu

doi:10.1371/journal.pone.0084580

Abstract

In plants, salicylic acid (SA) is a signaling molecule that regulates disease resistance responses, such as systemic acquired resistance (SAR) and hypertensive response (HR). SA has been implicated as participating in various biotic and abiotic stresses. This study was conducted to investigate the role of SA in adventitious root formation (ARF) in mung bean (Phaseolus radiatus L) hypocotyl cuttings. We observed that hypocotyl treatment with SA could significantly promote the adventitious root formation, and its effects were dose and time dependent. Explants treated with SA displayed a 130% increase in adventitious root number compared with control seedlings. The role of SA in mung bean hypocotyl ARF as well as its interaction with hydrogen peroxide (H2O2) were also elucidated. Pretreatment of mung bean explants with N, N’-dimethylthiourea (DMTU), a scavenger for H2O2, resulted in a significant reduction of SA-induced ARF. Diphenyleneiodonium (DPI), a specific inhibitor of membrane-linked NADPH oxidase, also inhibited the effect of adventitious rooting triggered by SA treatment. The determination of the endogenous H2O2 level indicated that the seedlings treated with SA could induce H2O2 accumulation compared with the control treatment. Our results revealed a distinctive role of SA in the promotion of adventitious rooting via the process of H2O2 accumulation. This conclusion was further supported by antioxidant enzyme activity assays. Based on these results, we conclude that the accumulation of free H2O2 might be a downstream event in response to SA-triggered adventitious root formation in mung bean seedlings.

Highlights

Roots function as the interface between plants and the terrestrial environment
The results indicated that exogenous salicylic acid (SA) could promote adventitious root formation, and its effects were dose and time dependent (Figure 1)
An inhibitory effect on ARF was observed when the SA concentration was 0.8 mM. These results indicate that exogenous SA at particular concentrations promotes adventitious root formation in mung bean hypocotyl cuttings

Summary

Introduction

Roots function as the interface between plants and the terrestrial environment. The root system is composed of primary roots, lateral roots and adventitious roots. Primary roots are initiated during embryogenesis and elongate after germination. Lateral roots and adventitious roots are ‘post-embryonic’ roots, as they initiate from non-pericycle tissues. Lateral roots initiate from primary roots or axes, and adventitious roots initiate from stem and leaf-derived cells. Together, these plant roots form the root system, the architecture of which can be altered in response to environmental changes and stimuli [1]

Methods

Results

Conclusion