A KINESIN-LIKE PROTEIN, KATAP, IN THE CELLS OF ARABIDOPSIS AND OTHER PLANTS

The kinesin-like proteins (KLPs) are a large family of plus- or minus- end-directed microtubule motors important in intracellular transport, mitosis, meiosis, and development. However, relatively little is known about plant KLPs. We prepared an antibody against two peptides in the microtubule binding domain of an Arabidopsis KLP (KatAp) encoded by t he KatA gene, one of a family of genes encoding KLPs whose motor domai n is located near the C terminus of the polypeptide. Such KLPs typical ly move materials toward the minus end of microtubules. An immunoreact ive band (M(r) of 140,000) corresponding to KatAp was demonstrated wit h this antibody on immunoblots of Arabidopsis seedling extracts. Durin g immunofluorescence localizations, the antibody produced weak, variab le staining in the cytoplasm and nucleus of interphase Arabidopsis sus pension cells but much stronger staining of the mitotic apparatus duri ng division. Staining was concentrated near the midzone during metapha se and was retained there during anaphase. The phragmoplast was also s tained. Similar localization patterns were seen in tobacco BY-2 cells, The antibody produced a single band (M(r) of 130,000) in murine brain fractions prepared according to procedures that enrich for KLPs (bind ing to microtubules in the presence of AMP-PNP but not ATP). A similar fraction from carrot suspension cells yielded a cross-reacting polype ptide of similar apparent molecular mass, When dividing BY-2 cells wer e lysed in the presence of taxol and ATP, antibody staining moved rapi dly toward the poles, supporting the presence of a minus-end motor, Mo vement did not occur without ATP, with AMP-PNP, or with ATP plus antib ody, Our results indicate that the protein encoded by KatA, KatAp, is expressed in Arabidopsis and is specifically localized to the midzone of the mitotic apparatus and phragmoplast. A similar protein is also p resent in other species.