Nitric oxide-associated protein 1-like (SlNOA1) suppresses dark-induced leaf senescence in tomato, a process...

Leaf senescence is a critical physiological process in plant growth and development, significantly impacting crop yield and quality. While the regulatory mechanisms of senescence involve multiple metabolic pathways and signaling cascades, the intricate network remains incompletely understood. In this study, we identified NO-associated protein 1-like (SlNOA1), a chloroplast-localized protein in tomato (Solanum lycopersicum), which contains a GTP-binding domain (G-CP domain) and belongs to the circularly permuted GTPase superfamily. Using CRISPR-Cas9 technology, we generated SlNOA1 knockout mutants (slnoa1) and demonstrated its role in leaf senescence. Loss of SlNOA1 results in a pale-green phenotype, reduces chlorophyll content and accelerates senescence, indicating its function as a negative regulator of senescence. Notably, we further discovered that SlNAP2 (NAC-like, activated by Apetala3/Pistillata 2), a positive regulator of senescence, binds to the SlNOA1 promoter and suppresses its expression. Additionally, SlNOA1 is functionally linked to ABA-induced senescence. Although the ABA receptor SlPYL4 does not directly interact with SlNOA1, it physically associates with SlNAP2. This interaction attenuates SlNAP2's suppression of SlNOA1, but ABA restores and enhances this inhibitory effect. These findings reveal that SlNOA1 and SlNAP2 form a negative feedback loop to fine-tune leaf senescence, dynamically regulated by the ABA-PYLs signaling pathway. Collectively, our study not only establishes the pivotal role of SlNOA1 in senescence but also provides novel insights into the ABA-mediated regulatory network governing this process.