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

Abstract

AbstractTip growth is a highly polarized growth process essential for plant growth and reproduction. However, its molecular mechanism and evolutional significance still remain elusive. Here, we show that plant-specific armadillo-repeat containing kinesin, MpARK1, drives long-range organelle transport and microtubule convergence in tip growing rhizoids in a basal land plant Marchantia polymorpha. MpARK1 is required for anterograde transport of the nucleus and plastids to maintain their position during persistent tip growth. Furthermore, MpARK1 participates in microtubule focusing on the apex to stabilize growth direction. MpARK1-dependent rhizoid growth is essential for plant anchorage and soil holding capacity. Thus, ARK might be co-opted to serve as a long-range transporter and intracellular organizer in the primitive rooting structure (rhizoid) for the adaptation to terrestrial environments. Our findings suggest that ARK was comparable to animal anterograde kinesin, challenging the traditional view that actomyosin-based cytoplasmic streaming is a dominant transport mode in plant kingdom.