Nitric oxide is involved in hydrogen gas-induced cell cycle activation during adventitious root formation in cucumber.

Abstract

Using cucumber (Cucumis sativus 'Xinchun 4') explants, this study examined how hydrogen-rich water (HRW) drives adventitious root organogenesis. A dose-dependent response was observed, with 50% HRW eliciting the greatest biological effect. HRW elevated nitric oxide (NO) levels in a time-dependent manner and promoted G1-to-S phase cell cycle transition. Expression of cell cycle regulators—CycA, CycB, CDKA, and CDKB—was upregulated by both HRW and exogenous NO. Application of a NO scavenger, a NOS-like enzyme inhibitor, or nitrate reductase inhibitors (tungstate and NaN3) partially reversed HRW-induced root formation, cell cycle activation, and associated gene expression changes. These findings indicate that NO functions as a downstream signaling component in the H2-mediated pathway governing adventitious root development.

Mechanism

HRW stimulates NO accumulation, which in turn promotes G1-to-S cell cycle transition by upregulating CycA, CycB, CDKA, and CDKB expression, thereby facilitating adventitious root organogenesis in cucumber explants.