Spatial control of cytokinesis in plant cells depends on guidance of the cytokinetic apparatus, the phragmoplast, to a cortical "division site" established before mitosis. Previously, we showed that the Tangled1 (Tan1) gene of maize is required for this process during maize leaf development (Cleary, A.L., and L.G. Smith. 1998. Plant Cell. 10:1875-1888.). Here, we show that the Tan1 gene is expressed in dividing cells and encodes a highly basic protein that can directly bind to microtubules (MTs). Moreover, proteins recognized by anti-TAN1 antibodies are preferentially associated with the MT-containing cytoskeletal structures that are misoriented in dividing cells of tan1 mutants. These results suggest that TAN1 protein participates in the orientation of cytoskeletal structures in dividing cells through an association with MTs.