messenger RNA (mRNA) 降解的調節對基因表現控制至關重要，其中 CCR4-associated factor 1 (CAF1)蛋白在脫腺苷酸化過程中(deadenylation)發揮著關鍵作用。然而，水稻 CAF1（OsCAF1）蛋白在逆境下於細胞內位置及其功能意義仍未明確。在本研究中，我們探討了高溫逆境下 OsCAF1 蛋白於細胞內位置的改變及其在耐熱逆境中的作用。在正常條件下，OsCAF1A、OsCAF1G 與 OsCAF1H 分散於細胞質中，而 OsCAF1B 則定位於processing bodies (PBs)。高溫逆境促使 OsCAF1A、OsCAF1G 與 OsCAF1H 位移至PBs及stress granules，顯示其在逆境反應中調控 mRNA 穩定性及降解的作用。基因表現量(absolute RT-qPCR)結果顯示，OsCAF1A 在水稻幼苗中表現量最為豐富，且在高溫逆境下會被進一步誘導表現。功能性分析結果表明，在高溫逆境下，OsCAF1A 的大量表現可以減少細胞電解質洩漏以提高幼苗存活率，來增強植株耐熱性。相對地， 當OsCAF1A 發生突變時，則使得植株對高溫更為敏感。然而，在正常生長條件下，OsCAF1A 的過度表現會導致植株矮化及穀物產量減少。交互作用(BiFC)實驗結果證實，兩種 DEAD-box RNA 解旋酶-OseIF4AIIb 與 OsRH8-均為與 OsCAF1A 具有交互作用的蛋白質因子，對OsCAF1A於細胞內位置分佈具有截然相反的影響：在高溫逆境下，OseIF4AIIb 會限制 OsCAF1A 聚集於 PB，而 OsRH8 則促進OsCAF1A 聚集於 PB。這些發現強調了 OsCAF1 蛋白在水稻耐熱性中的重要作用，並展示了其在提高作物對氣候變遷適應能力方面的潛力;The dynamic regulation of messenger RNA (mRNA) decay is crucial for gene expression control, with CCR4-associated factor 1 (CAF1) proteins playing a key role in deadenylation. However, the subcellular localization and functional sig-nificance of rice CAF1 (OsCAF1) protein under stress conditions remain largely uncharacterized. In this study, we investigated the re-localization of OsCAF1 proteins under high-temperature stress and their role in heat stress tolerance. Under normal conditions, OsCAF1A, OsCAF1G, and OsCAF1H were dispersed in the cytoplasm, whereas OsCAF1B localized to processing bodies (PBs). Heat stress triggered the re-localization of OsCAF1A, OsCAF1G, and OsCAF1H to PBs and stress granules, suggesting a role in stress-responsive mRNA regulation. Expression analysis revealed that OsCAF1A was the most abundantly expressed among OsCAF1 genes in rice seedlings, with its expression further induced by heat stress. Functional analysis demonstrated that OsCAF1A overexpression en-hanced heat tolerance by reducing electrolyte leakage and improving seedling survival, whereas OsCAF1A mutants exhibited increased sensitivity to heat stress. However, OsCAF1A overexpression lines also exhibited shorter plant height and reduced grain yield than wild type under normal growth conditions. Interaction studies identified OseIF4AIIb and OsRH8, two DEAD-box RNA helicases, as OsCAF1A-associated proteins with opposing effects on its re-localization: OseIF4AIIb restricted, whereas OsRH8 promoted OsCAF1A recruitment to PBs under heat stress. These findings highlight the crucial role of OsCAF1 proteins in rice thermotolerance and their potential for improving crop resilience to climate change.
