RGA1-Mediated Crosstalk of Hormonal, Metabolic, and Redox Networks Sustains Anther Fertility Under Drought Stress in Rice.

Abstract

The Gα subunit RGA1, a crucial component of heterotrimeric G proteins, has been well-documented to enhance drought resistance in rice seedlings. However, its role during the reproductive stages has remained unexplored. This study aimed to investigate the function of RGA1 in mitigating drought-induced defects in anther and pollen development during pollen mother cell meiosis with Zhonghua 11 (WT), a Gα-deficient mutant (d1), and an RGA1-overexpressing line (OE-1). Under severe drought stress, the three genotypes exhibited significantly decreased spikelet fertility, kernel weight, and grain yield. Concurrently, decreased pollen viability, photosynthetic efficiency, and plant water content were observed, while levels of hydrogen peroxide and malondialdehyde were elevated. Notably, the d1 mutants showed the strongest drought resistance by exhibiting the least physiological disturbances, outperforming both the WT and OE-1 lines. Compared with the d1 mutant, the anthers of drought-stressed WT and OE-1 lines showed significantly more pronounced decreases in carbohydrate contents, ATP levels, ATPase activity, energy charge, and indole acetic acid (IAA) levels. These results demonstrate that the deficiency of RGA1 enhances carbohydrate and energy metabolism, as well as the IAA levels, in anther tissues under drought stress. This enhancement leads to an improvement in the antioxidant capacity of rice plants to suppress the accumulation of peroxides, which ultimately alleviates drought-induced pollen sterility. Findings of this study indicate that RGA1 modulates drought resilience by coordinating hormones, sugars, and energy metabolism.