The 30th International Conference on Arabidopsis Research (ICAR 2019)

566 / 2019-03-21 11:00:08

SYP73 Is a Novel Membrane-Associated Actin-Binding Protein that Anchors ER Membrane to Actin Cytoskeleton

endoplasmic reticulum (ER),actin cytoskeleton,actin-binding protein

Plenary track > Cell Biology

In plant cells, the endoplasmic reticulum (ER) is the gateway to the secretory pathway and is a network that functionally connects nearly all the other membrane-bound organelles. The essential functions of the ER are fulfilled by its complex membrane architecture which constantly undergoes remodeling and moving mainly on actin and to a minor extent on microtubules. Although the actomyosin system has been suggested functional for ER movement, the mechanisms underlying stable interactions between the ER and the actin cytoskeleton are unclear. We demonstrate that SYP73, a member of the plant SNARE family, is a novel ER membrane-associated actin-binding protein. We show that overexpression of SYP73 causes a striking rearrangement of the ER over actin and that loss of SYP73 reduces ER streaming and affects overall ER network morphology and plant growth. A potential mechanism that regulates SYP73 functions has been investigated. Although conserved domain prediction tools did not detect any actin-binding domain in SYP73, we identified a fragment that is mainly responsible for SYP73 actin binding. Furthermore, the role of SYP73 in regulating actin reorganization has also been examined. We propose a model for plant ER remodeling whereby the dynamic rearrangement and streaming of the ER network depend on the propelling action of myosin‐XI over actin coupled with a SYP73-mediated bridging, which dynamically anchors the ER membrane with actin filaments.