Plant-specific armadillo repeat kinesin directs organelle transport and microtubule convergence to promote tip growth

Tip growth is essential for plant growth and reproduction. However, it remains elusive how highly polarized tip-growing cells coordinate the organization of intracellular components. Here, we show that plant-specific armadillo-repeat containing kinesin, MpARK, mediates organelle transport and microtubule convergence in tip growing rhizoids in the early diverging land plant Marchantia polymorpha . MpARK is required for anterograde transport of organelles to maintain their position. Furthermore, MpARK participates in the formation of microtubule foci at the rhizoid apex to stabilize growth direction. MpARK-dependent rhizoid growth is essential for plant anchorage and soil holding capacity. Thus, ARK might be a principal organelle transporter and intracellular organizer in the primitive rooting cells for the adaptation to terrestrial environments. Our findings suggest that ARK is functionally comparable to canonical anterograde kinesins in animals and fungi.