Genetic Dissection of Rice Plant-Specific Non-ε Group 14-3-3 Proteins in Response to Phosphate Starvation

The 14-3-3 proteins are highly conserved and widely distributed across eukaryotes. Some 14-3-3 proteins have been identified as regulators of phosphorus (Pi) deficiency tolerance in rice, but their diverse functions remain largely unexplored. In this study, we characterized the role of rice plant-specific non-ε group 14-3-3 proteins (OsGF14a-f) in response to Pi starvation by mutating these genes. We found that the expression of OsGF14a decreased in response to Pi starvation, while the expression of other non-ε group genes was induced. Subcellular localization studies transiently expressing them in tobacco leaves showed that OsGF14a was present in both the cytoplasm and nucleus, whereas the other proteins were predominantly localized in the cytoplasm. By developing single and multiple mutants, we demonstrated that OsGF14a plays a negative role in Pi homeostasis and root growth, while OsGF14b, OsGF14c and OsGF14f may act as positive regulators of Pi homeostasis and root growth in rice. However, all non-ε group 14-3-3 genes positively regulated rhizosphere acidification. Furthermore, the mutation of OsGF14a enhanced Pi accumulation and plant growth under various Pi supply conditions, likely due to the induction of OsPHR3, OsPT2 and OsPHO1;2 in the roots. Overall, this study highlights the diverse functions of plant-specific non-ε group 14-3-3 proteins in response to Pi starvation in rice and identifies the mutation of OsGF14a as a potential strategy to improve rice tolerance to Pi deficiency.