The Auxin Response Factor <i>OsARF25</i> Negatively Regulates Grain Size and Weight in Rice (<i>Oryza sativa</i> L.) by Activating the Expression of <i>SG1</i> and <i>OsOFP04</i>

Abstract

Grain size and grain weight are critical factors influencing crop yield. In rice (Oryza sativa L.), the auxin response factor (OsARF) family proteins, key components of the auxin signaling pathway, function as transcription factors and play essential roles in regulating various plant growth and development processes, including seed development. Here, we identified that Oryza sativa AUXIN RESPONSE FACTOR 25 (OsARF25) plays an essential role in regulating grain size and grain weight by activating the expression of SHORT GRAIN 1 (SG1) and Oryza sativa OVATE FAMILY PROTEIN 04 (OsOFP04). The osarf25 mutants showed larger grains with increased grain length, grain width, and 1000-grain weight. Furthermore, molecular evidence demonstrated that OsARF25 functions as a transcriptional activator. RNA-seq analysis further identified its target genes SG1 and OsOFP04. In addition, OsARF25 directly binds to the promoters of SG1 and OsOFP04 and activates their expression. Further, the osarf25 mutant exhibited enhanced sensitivity to brassinolide treatment, confirming that the targeting of SG1 and OsOFP04 by OsARF25 mediates BR signaling. Taken together, our study revealed that OsARF25 functions as a regulator of grain length, grain width, and grain weight by participating in the BR signaling pathway, and it has potential value for molecular breeding in rice.

Keywords

• OsARF25
• grain size
• grain weight
• BR signaling pathway
• rice