Recruitment of SH3P2-DRP1A by HYCCIN2 Drives Membrane Tubulation in Arabidopsis Embryonic Cell Plate Formation

Cytokinesis marks the culmination of cell division when the cytoplasm undergoes division to yield two daughter cells. This intricate process encompasses various biological phenomena, including the organization of the cytoskeleton and the dynamics of vesicles. The development of the cell plate aligns with alterations in the cytoskeleton structure and vesicles derived from the trans-Golgi, ultimately resulting in the formation of the planar cell plate. Nevertheless, the coordination of these processes in plants remains to be determined. Here, we introduce HYCCIN-CONTAINING2 (HYC2) as a pivotal cytoskeleton cross-linking protein that accumulates at phragmoplasts and plays a crucial role in cell plate formation. A genetic study involving the depletion of HYC2 post-anaphase in Arabidopsis revealed HYC2s function in cell plate formation. HYC2 interacted with dynamin-related protein 1A (DRP1A) and SH3 domain-containing protein 2 (SH3P2), essential for membrane tubulation during cell plate formation. The recruitment of SH3P2 and DRP1A to the cell plate and phragmoplast organization was compromised in homozygous hyc2-2 mutant globular embryos. Our results shed light on the cytoskeletal function of HYC2 in assembling the cell plate, potentially by guiding vesicles containing SH3P2-DRP1A to the planar cell plate. Significance statementDuring plant cell division, a new membrane is constructed at the division plane, and vesicles fuse to form a transient compartment known as the cell plate. This structure undergoes stabilization via membrane remodeling events, including tubulation, to generate robust membrane intermediates. Apart from DRP1A and SH3P2, our understanding of other protein components involved in membrane remodeling still needs to be completed. HYC2 is a plant counterpart to the human Hyccin protein involved in neuronal myelination and displaying bundling capabilities for microtubules and microfilaments. Our study demonstrates that HYC2 is crucial in recruiting proteins during membrane tubulation in the cell plate formation in developing Arabidopsis embryos. These findings underscore the molecular function and vital role of the Hyccin protein in cell plate formation. One Sentence SummaryPlant HYC2 displays bundling capabilities for microtubules and microfilaments to recruit DRP1A and SH3P2 during membrane tubulation in the cell plate formation in developing Arabidopsis embryos.