A ticket for the live show: microtubules in male gametophyte development.

Microtubule-reporter plants expressing green fluorescent protein-α-TUBULIN fusion protein (GFP-TUA6) in male gametophytic cells of tobacco and Arabidopsis provide new tools for studying the native organization of microtubule (MT) arrays during reproductive development. These plants reveal unique features of gametophytic MT arrays including a basket-like cortical MT array in polarized microspores at interphase, an asymmetric spindle and curved phragmoplast MTs at microspore division and an assembly of bundled cortical MTs during germ cell morphogenesis. The application of these MT-reporter plants has been demonstrated by RNAi-mediated knockdown of the microtubule-associated protein TMBP200, the tobacco orthologue of the conserved MAP215/Dis1 family protein. The double transgenic lines display defects in nuclear positioning, division asymmetry and cytokinesis that are associated with striking defects in spindle and phragmoplast position and organization. This study reveals native and altered MT arrays in unprecedented detail and clarifies the essential functions of MAP215/Dis1 protein function in successive steps in male germline establishment. Such gametophytic MT-reporter lines should accelerate studies of the dynamic regulation of MT arrays by microtubule associated proteins and other effectors during male gametophyte development.