Abstract
Organization of plant specific microtubule (MT) structures, such as cortical MTs, MTs in cytoplasmic strands, preprophase MT bands, spindle and phragmoplasts, requires MT-regulating proteins, so-called microtubule-associated proteins (MAPs). We have tried to find such proteins using tobacco BY-2 cells and succeeded in isolating them biochemically, namely, 65 kDa MAP, 190 kDa protein, 210 kDa tobacco MOR1 homolog (TMBP200). The 65 kDa MAP induces MT bundlin. Immunofluorescence microscopy revealed ubiquitous location along with MT throughout the cell-cycle and immunoelectron microscopy suggested that the 65 kDa MAP cross-linked cortical MTs. The 190 kDa protein exists in interphase nucleus, spindle and phragmoplasts. It has affinity to both MTs and actin, but the function is unclear. The 210 kDa protein has an ability to promote tubulin polymerization. Structure and function of such proteins will be discussed with recent results.
