Genetic regulation of rice minor vein patterning by the OsIDD14/12/13 protein complex

INDETERMINATE DOMAIN (IDD) transcription factors play important and diverse roles in plant growth, development, and stress responses. For example, OsIDD12 and OsIDD13 associate with SHORT ROOT transcription factors to mediate the expression of the auxin influx transporter gene OsPIN5c in rice (Oryza sativa), thereby regulating minor vein differentiation. However, the underlying mechanism is unclear. In this study, we demonstrate that OsIDD14 associates with OsIDD12 and OsIDD13 to regulate minor vein patterning in rice. In situ hybridization and GUS reporter assays revealed that OsIDD14 expression is restricted to the rice vasculature. The osidd12 osidd13 osidd14 triple mutant exhibited a minor vein pattern similar to that of C₄ grasses. We demonstrate that OsIDD14 forms a heterogeneous protein complex with OsIDD12 and OsIDD13 that suppresses OsPIN5c expression and inhibits minor vein formation. Ectopic expression of OsIDD14 rescued the phenotypes of the osidd12 osidd13 double mutant, revealing the functional redundancy of rice IDD12, 13, and 14. In summary, these study reveals that OsIDD14 plays a pivotal role in minor vein patterning and has pleiotropic functions in rice, and laying the foundation for developing rice with high vein density.