Pollen tube taxol dependent structures co-assemble with neuronal HMW MAPs (MAP2)

Pollen tube microtubules (MTs) are as dynamic as animal MTs and they may in teract with plasma membrane, endoplasmic reticulum, Golgi apparatus, mitoco ndria and a variety of cytoplasmic proteins. Bridges connecting MTs to each other and to membranes have been documented in pollen tubes by electron mi croscopy; however, the biochemical and molecular nature of these linkages i s not known. In other cell types interaction between organelles and MTs req uire the participation of Microtubule-Associated Proteins (MAPs) that bridg e the cytoskeleton to these organelles. Although biochemical documentation of such bridging MAPs in plant cells is lacking, it is reasonable to assume , by analogy with the animal systems, that specialized MAPs regulate MTs po lymerization and dynamic in pollen tube. As a first step toward testing thi s hypothesis, the ability of Nicotiana tabacum pollen tube taxol-stabilized MTs to bind mammalian brain High Molecular Weight MAPs (HMW-MAPs) (MAP2) w as tested. This association analysis revealed the presence of mammalian MAP 2-binding sites on pollen tube taxol-induced structures suggesting that the association presumably occurs at conserved domains on the tubulin molecule s.