The 14-3-3 Protein OsGF14h Coordinates Brassinosteroid and Gibberellin Signaling to Regulate Plant Growth and Grain Yield in Rice.

Brassinosteroids (BRs) and gibberellins (GAs) are two important phytohormones that regulate plant growth and development. Crosstalk between BR and GA has been unveiled in Arabidopsis but the molecular mechanism by which the concurrence of these two signaling pathways regulates plant growth and development in rice remains elusive. The14-3-3 proteins are a family of conserved molecules that interact with a number of protein clients to regulate fundamental cellular processes including different aspects of plant hormone physiology. Here, we report that the rice 14-3-3 protein OsGF14h (G-box factor 14-3-3 homolog h) negatively modulates BR response and positively regulates GA signaling in rice. Overexpressing OsGF14h in rice increased plant height and grain yield, whereas knocking out OsGF14h increased lamina joint angle and reduced plant height and grain yield. OsGF14h interacted with both OsOFP8, a positive regulator in BR signaling, and SLR1, a negative key regulator in GA signaling. Interaction with OsGF14h led to nuclear export and cytoplasmic retention of OsOFP8, whereas OsGF14h interaction resulted in SLR1 shuttling from the nucleus to the cytoplasm and consequently inducing degradation of SLR1. Our results indicate that OsGF14h functions in both BR and GA signaling pathways and acts as a crosstalk point for BR and GA signaling, which offers new insights into the role of 14-3-3 proteins in regulating plant growth and development by modulating BR and GA signaling crosstalk.