Abstract
Proper regulations of cell number and shape are essential for normal development in multicellular organisms. Spatial and temporal controls of microtubules are prominent molecular mechanisms managing these cellular processes. Sister Type II ubiquitin-like proteins, PUBL1 and PUBL2 are expressed in meristematic cells in the moss Physcomitrella patens and are essential for proper cell division and elongation via organization of microtubule arrays. To understand the molecular mechanism of microtubule organization, we have analyzed molecular function of PUBLs.
Double disruption of PUBL1 and PUBL2 retarded the collapse of phragmoplasts. In the wild type, the phragmoplast is composed of antiparallel microtubules that overlap and closslink at its equatorial plane. In the phragmoplasts of the disruptants, the overlapping microtubules were expanded. The PUBLs-GFP fusion proteins were localized to the phragmoplast equator. Thus we propose that PUBLs regulate the stability of phragmoplast microtubules by acting on antiparallel microtubules at the phragmoplast equator.
