OsOSCA2.4 regulates post-Golgi trafficking of storage proteins by modulating Ca2+ homeostasis in rice endosperm

  • Plant Cell. 2026 Jun 27:koag193. doi: 10.1093/plcell/koag193.
Yu Zhang  1 ,  Yun Zhu  2 ,  Pengcheng Zhang  1 ,  Wang Tian  3 ,  Hui Dong  1 ,  Zebin Liu  4 ,  Yu Chen  2 ,  Xiuhao Bao  1 ,  Tian Pan  1 ,  Yehui Xiong  2 ,  Xin Wang  2 ,  Zhijie Ren  3 ,  Xiaokang Jiang  1 ,  Xiaohang Han  2 ,  Ruonan Jing  1 ,  Hongming Wu  1 ,  Chuanwei Gu  1 ,  Rongbo Chen  1 ,  Xiaoli Chen  1 ,  Jie Lei  1 ,  Erchao Duan  1 ,  Cailin Lei  2 ,  Zhijun Cheng  2 ,  Jiachang Wang  2 ,  Yiqun Bao  5 ,  Chuanyin Wu  2 ,  Haiyang Wang  2 ,  Yihua Wang  1 ,  Yulong Ren  2 ,  Jianmin Wan  1  2
Affiliations
  • 1. State Key Laboratory for Crop Genetics & Germplasm Enhancement and Utilization, Zhongshan Biological Breeding Laboratory, Jiangsu Nanjing Rice Germplasm Resources National Field Observation and Research Station, Nanjing Agricultural University, Nanjing 210095, China.
  • 2. State Key Laboratory of Crop Gene Resources and Breeding, National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
  • 3. State Key Laboratory of Protein and Plant Gene Research, School of Advanced Agricultural Sciences, Peking University, Beijing 100871, China.
  • 4. College of Life Science, Capital Normal University, Beijing 100048, China.
  • 5. College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China.
PMID: 42364252 DOI: 10.1093/plcell/koag193
Abstract

Seed storage proteins (SSPs), which accumulate specifically during seed development, constitute a major source of plant-derived protein in the human diet. Despite their critical role in determining crop quality, the molecular mechanisms underlying the intracellular trafficking of SSPs remain poorly understood. Here, we characterize the rice glutelin precursor accumulation16 (gpa16) mutant, which exhibits defective dense vesicle (DV)-mediated post-Golgi trafficking of proglutelins, resulting in their overaccumulation in the apoplast. GPA16 encodes OsOSCA2.4, a member of the reduced hyperosmolality-induced Ca2+ increase channel (OSCA) family. OsOSCA2.4 localizes to post-Golgi compartments including the trans-Golgi network (TGN) and prevacuolar compartment (PVC) in vegetative tissue, and DVs in the endosperm. The OsOSCA2.4(P397L) variant disrupts the formation of the Rab5a molecular module, a process influenced by intracellular Ca2+ homeostasis. Ca2+ imaging assays indicate that OsOSCA2.4 functions as a regulator of Ca2+ homeostasis of PVCs/DVs, the primary sites of Rab5a module activity. Genetic analyses reveal functional redundancy between OsOSCA2.4 and OsOSCA4.1 in modulating post-Golgi trafficking of proglutelins. Collectively, our findings identify OSCA-mediated Ca2+ homeostasis as a previously unrecognized regulatory layer governing post-Golgi trafficking of SSPs and uncover an unexpected role for OSCA proteins in vesicular trafficking in eukaryotes.

Keywords
Ca2+ homeostasis; Post-Golgi trafficking; Seed storage proteins.
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