| 研究実績の概要 |
VPS13a was previously identified in my research that it is involved in pollen germination step. My recent research progress has shown that only VPS13a but not its close paralog, VPS13b, played major role in pollen germination. Also, a pollen which lack functional copy of VPS13a fertilized an ovule at significantly lower rate than the pollen with functional VPS13a. This finding suggests that Arabidopsis, and likely other flowering plants, has specifically developed a specific form of VPS13 (VPS13a in this case) to rely on its unique function in reproduction process.
Protein domain annotation suggested that VPS13a contained a Ca2+-dependent lipid-binding C2 domain not found in VPS13b. I used CRISPR/Cas9-mediated genome editing to truncate C2 domain from VPS13a gene. The pollen from mutant plant germinate inefficiently suggesting the importance of C2 domain in VPS13a function. I also used biomolecular Ca2+ sensor to show that VPS13a was not required to trigger post-pollination pollen Ca2+ dynamic, thus VPS13a potentially functions downstream of Ca2+ signal.
Yeast and human VPS13s were shown to function as tethering molecule between organelles. I also explore this possibility in Arabidopsis VPS13a by using transmission electron microscopy to observe pollen after pollinated on a pistil. Interestingly, germinating wild-type pollen showed pollen grain-wide lipid body (LB) dissociation from rough endoplasmic reticulum (rER). This was rarely observed in a mutant vps13a pollen, thus suggests that VPS13a may control the dynamic between LB and rER though its tethering activity.
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