Nuclear Architecture Related 1-Dependent H₂ Reshapes Root Plasticity Through Targeting Root Meristem Cell Division...

Root system architecture plasticity is critical for optimizing anchorage and nutrient and water uptake. However, whether and how biogenic molecular hydrogen (H₂) influences root plasticity remains further explored. Here, using ABA-inhibited plant root growth as a research model, we show that Arabidopsis hydrogenase Nuclear Architecture Related 1 (NAR1)-dependent H₂ reshapes root plasticity. First, we observed that NAR1 overexpression promotes primary root elongation and meristem cell division, whereas RNAi-NAR1 lines show impaired root growth, particularly upon ABA administration. Consistently, ABA-inhibited CYCB1;1 expression, a G2/M marker, was substantially recovered or aggravated in OE-NAR1 or RNAi-NAR1 lines. Further analysis revealed that NAR1 preserves DR5 activity, and AUX1, PIN1, and PIN2 signals under ABA. In parallel, NAR1 sustains cellular homeostasis by limiting ABA-triggered oxidative stress, as evidenced by upregulation of antioxidant defense and reduced ROS and lipid peroxidation. The functional requirement for NAR1-derived H₂ was further corroborated by H₂ supplementation, which effectively rescued the inhibited phenotypes of RNAi-NAR1 lines. Together, our findings reveal a convergence of meristem cell division activity, auxin signaling and ROS homeostasis governed by NAR1-dependent H₂, which reshapes root plasticity under ABA treatment. These observations provide new molecular insights into endogenous H₂ signaling for shaping plant plasticity in complex environments.