In eukaryotic cells microtubule (MT) length is determined by polymerization and depolymerization phases. One important parameter for length determination is the contact with the cell cortex. Here, we show in the model organism Aspergillus nidulans that the contact of MT plus ends with the cortex is mediated through interaction between a putative MT polymerase (XMAP215, A. nidulans homologue AlpA), and a cortical cell end marker protein, TeaA. Although both proteins localized to MT plus ends during MT growth, AlpA-TeaA interaction was observed in a bimolecular fluorescence complementation assay only after MT plus ends contacted the cortex. In the absence of TeaA, MT plus ends contacted random places along the tip cortex and occasionally continued to grow after reaching the cortex. In the absence of AlpA, the microtubule array was laregely affected and MTs grew very slowly. In an in vitro MT polymerase assay we show that fast MT polymerization depends on the presence of AlpA and is inhibited by TeaA. Further investigation with truncated variants of TeaA suggests that the interaction of TeaA with AlpA is necessary not only for the proper behavior of MTs at tips but also proper polarity establishment and maintenance.
Full conference title:
10th EUROPEAN CONFERENCE ON FUNGAL GENETICS
- ECFG 10th (2010)