Dual Localization and Functional Divergence of V-ATPase Subunit A: Nuclear Shuttling Mediates Distinct Roles in Dark- and MeJA-Induced Leaf Senescence

Retrograde signaling regulates plant senescence, but the role of vacuoles in this process remains unclear. Here, we demonstrate that rice vacuolar H⁺-ATPase subunit A (OsVHA-A) localizes to both the cytoplasm and nucleus. Sucrose treatment increased OsVHA-A expression and nuclear accumulation, while darkness reduced it. Methyl jasmonate (MeJA) initially promoted OsVHA-A nuclear translocation but decreased it upon prolonged exposure. Downregulation of OsVHA-A expression accelerated MeJA-induced rice leaf senescence but delayed darkness-induced senescence. MeJA treatment also significantly upregulated the expression of OsMYC2 and OsMAPK6 in OsVHA-A-RNAi plants compared to wild-type plants. Moreover, OsVHA-A downregulation notably increased the level of expression of genes associated with sugar signaling and transport under dark conditions. Immunoprecipitation–mass spectrometry and molecular docking analyses identified interactions between OsVHA-A and OsTPR1, OsMed14, sucrose transporters, and enzymes involved in sucrose metabolism. The binding of OsVHA-A with OsTPR1 and OsSUS1 was confirmed by BiFC. These findings highlight the multifunctional role of OsVHA-A in coordinating organelles and nuclear signaling, providing new insights and potential strategies for manipulating senescence to improve rice yield and quality.