Identification of a novel family of 70 kDa microtubule‐associated proteins in Arabidopsis cells

Publisher Website
Google Scholar
Abstract
Summary: Most plant microtubule‐associated proteins (MAPs) have homologues across the phylogenetic spectrum. To find potential plant‐specific MAPs that will have evaded bioinformatic searches we devised a low stringency method for isolating proteins from an Arabidopsis cell suspension on endogenous taxol‐microtubules. By tryptic peptide mass fingerprinting we identified 55 proteins that were enriched on taxol‐microtubules. Amongst a range of known MAPs, such as kinesins, MAP65 isoforms and MOR1, we detected ‘unknown’ 70 kDa proteins that belong to a family of five closely related Arabidopsis proteins having no known homologues amongst non‐plant organisms. To verify that AtMAP70‐1 associates with microtubules in vivo, it was expressed as a GFP fusion. This confirmed that the protein decorates all four microtubule arrays in both transiently infected Arabidopsis and stably transformed tobacco BY‐2 suspension cells. Microtubule‐directed drugs perturbed the localization of AtMAP70‐1 but cytochalasin D did not. AtMAP70‐1 contains four predicted coiled‐coil domains and truncation studies identified a central domain that targets the fusion protein to microtubules in vivo. This study therefore introduces a novel family of plant‐specific proteins that interact with microtubules.