Abstract
TBK5 is a higher plant-specific kinesin constantly expressed in tobacco BY-2 cells. On the basis of the finding that, in transiently transformed BY-2 protoplasts green fluorescent protein-tagged TBK5 (GFP-TBK5) proteins tend to form aggregates that function as microtubule-organizing centers (Goto and Asada, 2007), we hypothesize that TBK5 might be involved in nucleation of microtubules and/or the regulation of microtubule arrangement. To estimate the subcellular distribution of TBK5, we prepared stably transformed BY-2 cells that inducibly express GFP-TBK5 proteins, and examined the distribution of expressed GFP-TBK5 in interphase and mitotic cells. In interphase cells, GFP-TBK5 co-localized with peri-nuclei microtubules, microtubules in cytoplasmic strand, cortical and preprophase band microtubules. In mitotic cells, it co-localized with microtubules of mitotic spindle and phrogmoplast. Interestingly, the distribution of GFP-TBK5 along phragmoplast microtubules was not uniform, and biased toward their minus end. This pattern is similar to the reported distribution pattern of gamma-tubulin. We now carry out knock down experiments to test the above-mentioned hypothesis.
