Wound-induced signals regulate root organogenesis in Arabidopsis explants.

Background: Reactive oxygen species (ROS) and calcium ions (Ca) are representative signals of plant wound responses. Wounding triggers cell fate transition in detached plant tissues and induces de novo root organogenesis. While the hormonal regulation of root organogenesis has been widely studied, the role of early wound signals including ROS and Ca remains largely unknown.

Results: We identified that ROS and Ca are required for de novo root organogenesis, but have different functions in Arabidopsis explants. The inhibition of the ROS and Ca signals delayed root development in detached leaves. Examination of the auxin signaling pathways indicated that ROS and Ca did not affect auxin biosynthesis and transport in explants. Additionally, the expression of key genes related to auxin signals during root organogenesis was not significantly affected by the inhibition of ROS and Ca signals. The addition of auxin partially restored the suppression of root development by the ROS inhibitor; however, auxin supplementation did not affect root organogenesis in Ca-depleted explants.

Conclusions: Our results indicate that, while both ROS and Ca are key molecules, at least in part of the auxin signals acts downstream of ROS signaling, and Ca acts downstream of auxin during de novo root organogenesis in leaf explants.