Stress-associated protein OsSAP5 regulates rice heading date through interacting with OsGF14c in rice

Xiaobo Zhu^1,2Min Chen¹Zhang Dong^1,3Yihan Liu^1,2Qingshan Mou^1,3Farwa Basit⁴Jiaxin Liu^1,2Jin Hu²Yajing Guan^1,2*

• ¹Institute of Crop Science, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, China, Hangzhou, China
• ²Hainan Institute, Zhejiang University, Sanya, Hainan Province, China
• ³Hainan Yazhou Bay Seed Laboratory, Hainan Institute, Zhejiang University, Hainan, China
• ⁴Department of Biology, College of Science and Technology, Wenzhou-Kean University, Wenzhou 325060, China, Wenzhou, Zhejiang Province, China

Heading date, a critical agronomic trait determining rice regional adaptation and yield potential, is regulated by complex genetic networks. Although stress-associated proteins (SAPs) are well-documented mediators of abiotic stress responses, their roles in reproductive development remain poorly characterized. Here, we demonstrate that stress-associated protein 5 (OsSAP5) functions as a positive regulator of heading date in rice. Loss-of-function ossap5 mutants exhibited significant heading delay under natural short day conditions, accompanied by marked downregulation of florigen genes Hd3a and RFT1, and subsequent suppression of MADS-box genes in the shoot apical meristem (SAM). The similar decrease in expression of florigen genes was observed in OsGF14c overexpression lines under short day condition. The molecular and biochemical assays confirmed that OsSAP5 interacts with OsGF14c. Notably, OsSAP5 had the E3 ubiquitin ligase activity, and might promote the ubiquitination of OsGF14c.Therefore, OsSAP5 regulates heading date by interacting with OsGF14c under short day condition.