Nishina, M. | Search bioRxiv

bioRxiv2018

Chromosome missegregation causes somatic polyploidization in plants

Lagging chromosome is a hallmark of aneuploidy arising from errors in the kinetochore-spindle attachment in animal cells. However, kinetochore components and cellular phenotypes associated with kinetochore dysfunction are much less explored in plants. Here, we carried out a comprehensive characterization of conserved kinetochore components in the moss Physcomitrella patens and uncovered a distinct scenario in plant cells regarding both the localization and cellular impact of the kinetochore proteins. Most surprisingly, knock-down of several kinetochore proteins led to polyploidy, not aneuploidy, through cytokinesis failure in >90% of the cells that exhibited lagging chromosomes for several minutes or longer. The resultant cells, containing two or more nuclei, proceeded to the next cell cycle and eventually developed into polyploid plants. As lagging chromosomes have been observed in various plant species in the wild, our observation raised a possibility that they could be one of the natural pathways to polyploidy in plants.

cell biology↗

bioRxiv2017

Multiple kinesin-14 family members drive microtubule minus-end-directed transport in plant cells

Minus-end-directed cargo transport along microtubules (MTs) is exclusively driven by the molecular motor dynein in a wide variety of cell types. Interestingly, plants have lost the genes encoding dynein during evolution; the MT motors that compensate for dynein function are unknown. Here, we show that two members of the kinesin-14 family drive minus-end-directed transport in plants. Gene knockout analyses of the moss Physcomitrella patens revealed that the plant-specific class-VI kinesin-14, KCBP, is required for minus-end-directed transport of the nucleus and chloroplasts. Purified KCBP directly bound to acidic phospholipids (PLs) and unidirectionally transported PL liposomes along MTs in vitro. Thus, minus-end-directed transport of membranous cargoes might be driven by their direct interaction with this motor protein. Newly nucleated cytoplasmic MTs represent another known cargo exhibiting minus-end-directed motility, and we identified the conserved class-I kinesin-14 (ATK) as the motor involved. These results suggest that kinesin-14 motors were duplicated and developed as alternative MT-based minus-end-directed transporters in land plants.

cell biology↗