Abstract
A mature tracheary element (TE), a component of vessels and tracheids, is a hollow dead cell and its differentiation process includes a unique cell death program in which vacuole rupture triggers the execution of cell death. To clarify the mechanism of vacuole rupture during TE differentiation, we have analyzed vacuolar membrane dynamics using Arabidopsis cultured cell line expressing GFP-AtRab75 during cell death. Time-lapse imaging revealed that (1) the vacuolar membrane continues to move and fuse dynamically until cell death, (2) at the final stage it ceases moving once, and (3) it dramatically shrinks to disappear. In order to elucidate its molecular mechanisms, we focused on several Rab GTPases and analyzed their function in the vacuolar membrane dynamics during TE differentiation. We also carried out genetic analysis of Arabidopsis mutants defective in the endocytic pathway. Based on our recent results, we will discuss the mechanism of vacuole rupture during TE differentiation.
