Armadillo-repeat kinesin1 interacts with Arabidopsis atlastin RHD3 to move ER with plus-end of microtubules

Jiaqi Sun,Xingyun Qi,Mi Zhang,Caitlin Doyle,Huanquan Zheng

doi:10.1038/s41467-020-19343-2

Abstract

In living cells, dynamics of the endoplasmic reticulum (ER) are driven by the cytoskeleton motor machinery as well as the action of ER-shaping proteins such as atlastin GTPases including RHD3 in Arabidopsis. It is not known if the two systems interplay, and, if so, how they do. Here we report the identification of ARK1 (Armadillo-Repeat Kinesin1) via a genetic screen for enhancers of the rhd3 mutant phenotype. In addition to defects in microtubule dynamics, ER organization is also defective in mutants lacking a functional ARK1. In growing root hair cells, ARK1 comets predominantly localize on the growing-end of microtubules and partially overlap with RHD3 in the cortex of the subapical region. ARK1 co-moves with RHD3 during tip growth of root hair cells. We show that there is a functional interdependence between ARK1 and RHD3. ARK1 physically interacts with RHD3 via its armadillo domain (ARM). In leaf epidermal cells where a polygonal ER network can be resolved, ARK1, but not ARK1ΔARM, moves together with RHD3 to pull an ER tubule toward another and stays with the newly formed 3-way junction of the ER for a while. We conclude that ARK1 acts together with RHD3 to move the ER on microtubules to generate a fine ER network.

Highlights

In living cells, dynamics of the endoplasmic reticulum (ER) are driven by the cytoskeleton motor machinery as well as the action of ER-shaping proteins such as atlastin GTPases including ROOT HAIR DEFECTIVE3 (RHD3) in Arabidopsis
Chemical and protein–protein interaction analyses, we show that armadillo-repeat kinesin 1 (ARK1) interacts with RHD3 via its armadillo domain to lead the growth of the ER tubule together with the growing tip of microtubules for the generation of a fine ER network in plant cells
It is generally believed that in plant cells, dynamics of the ER is largely driven by the actin–myosin system[8,9,10,11], limited evidence suggested that microtubules play a role, in particular, in rapid growing cells[12,13]

Summary

Introduction

Dynamics of the endoplasmic reticulum (ER) are driven by the cytoskeleton motor machinery as well as the action of ER-shaping proteins such as atlastin GTPases including RHD3 in Arabidopsis. It is not known if the two systems interplay, and, if so, how they do. The network of the ER is highly dynamic and undergoes continuous reorganization, including tubule formation, extension, fusion, and sliding for ring closure[1,2]. No MT–ER connecting molecules have been identified in plant cells

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