The kinesin motor KipA is required for polarized growth in Aspergillus nidulans.
Motor proteins are key factors in various dynamic processes in eukaryotic cells. To analyze organelle movement over long distances, we are studying the function of different kinesins inA. nidulans. So far two mitotic kinesins, BimC and KlpA were described. Taking advantage of the genomic DNA sequencing project at Cereon Genomics, gene fragments corresponding to four new kinesins, designated KifA, KipA, KipB and KinA, were identified. The further results obtained for KipA will be presented here. KipA displayed highest homology to KIF3C from rat, which is involved in vesicle transport, and to Kip2p that is involved in nuclear migration and spindle orientation. KipA was predicted to form a dimer, and a KipA-GFP fusion protein was predominantly found in the cytoplasm. After ATP-depletion of the cell (uncoupling with CCCP), a fraction of KipA localized to cytoplasmic microtubules. In order to assign a function to KipA, we deleted the motor domain of KipA from the genome of A. nidulans and studied the dynamics of microtubules, mitochondria and nuclei by GFP technology. We did not detect any differences in those processes in comparison to wt-strains. However, we observed a strong effect on polarized growth. Whereas the radial colony extension rate appeared similar to wild type, the directionality of the hyphae in kipA mutants was dramatically changed. Hyphae displayed a meandering growth phenotype, suggesting an effect of the kinesin deletion on the positioning of the Spitzenkorper. To further analyse the roles of KipA and possible overlapping functions with other motors, we constructed double and multiple mutations of KinA, KipA, KipB and Dynein. The analyses of their phenotypes are on the way.
Fungal Genet. Newsl. 50 (Supl):abstract
Full conference title:
22nd Fungal Genetics Conference