Truncated OsVHA-c promotes drought stress tolerance in rice

Rice is extremely sensitive to drought, a major abiotic stress that critically affects crop yield. Vacuolar-type H⁺-ATPases (v-ATPases) are ATP-dependent proton pumps responsible for energizing secondary transport processes. Genes encoding different v-ATPases subunits have been implicated in responses to abiotic stresses. Nevertheless, there are no reports on the role of OsVHA-c in drought tolerance in rice. In this study, we generated truncated OsVHA-c lines (ΔOsVHA-c) using CRIPSR-Cas9 technology and overexpression lines in Nipponbare (Oryza sativa) background to investigate the physiological and molecular involvement of OsVHA-c under drought stress. Compared to wildtype, the ΔOsVHA-c lines demonstrated enhanced drought stress tolerance, exhibiting no senescence in younger leaves, higher CO₂ assimilation rates and water use efficiency, and lower oxidative stress, without developmental penalties. Furthermore, changes in ionomic composition indicated altered ion homeostasis in the ΔOsVHA-c lines. These lines also exhibited a higher stomatal density, although the stomata were smaller. This characteristic could potentially enable more efficient stomatal movement and a faster response to drought stress. A gene involved in the synthesis of phosphatidylinositol 3,5-bisphosphate, a molecule that is essential for vacuolar convolution, was identified as down-regulated in ΔOsVHA-c lines, possibly impairing the fragmentation of a few large vacuoles into multiple small vesicles. Our findings showed that truncated OsVHA-c enhanced the drought stress tolerance in rice plants, likely due to a combined effect of the morphological, physiological, and metabolic alterations. These results provide a promising avenue in adaptive breeding to global climate change.