OsDRP1C mediates root development by modulating OsPIN1 cycling in rice.

Root length plays a crucial role in plants' ability to absorb water and nutrients from the soil. However, the molecular mechanisms underlying root elongation in rice (Oryza sativa) remain unclear. Here, we identified a short root mutant, short root-31 (sr31), and cloned the causal gene by map-based cloning, which carries a point mutation in the coding sequence of DYNAMIN-RELATED PROTEIN 1C (OsDRP1C). Genetic complementation analyses demonstrated that OsDRP1C is responsible for the phenotypic defect of sr31. OsDRP1C is widely expressed in roots, with higher expression in root meristem, epidermal cells and vascular bundles. Colocalization analysis revealed that OsDRP1C is present in the plasma membrane (PM) and endomembrane system. FM4-64 internalization assay showed that endocytosis is inhibited in sr31. Further study indicated that OsDRP1D and OsDRP1E are also involved in root elongation; OsDRP1C interacts directly with OsDRP1D/E, and they function additively on root elongation. Furthermore, we showed that the trafficking and recycling of OsPIN1b between endomembrane and PM localization are attenuated in sr31, which affects auxin polar transport. These results provided the first insights into the molecular mechanism of OsDRP1C modulating OsPIN1b cycling in regulating root elongation, expanded our understanding of OsDRP1s' association with membrane protein trafficking in rice.