Poster: Cytoskeleton: Structure & Function

Abs # 1111: Structure and function of a 65 kDa microtubule-associated protein

Presenter:	Sonobe, Seiji , sonobe@sci.himeji-tech.ac.jp
Authors	Sonobe, Seiji  (A)   Sawano, Masahide  (A)   Iseki, Yoshito  (A)   Smertenko, Andrei  (B)   Hussey, Patrick  (B)   Shimmen, Teruo  (A)
Affiliations:	(A): Himeji Institute of Technology (B): University of Durham

MAP65 was first purified from tobacco cultured BY-2 cells and found ubiquitous existence in a variety of plants. It bundles microtubules (MTs) by forming cross-bridge structures between adjacent MTs. The space between MTs was 30 nm, which was consistent with that between cortical MTs (CMTs) in cells, suggesting that this MAP functions in organization of CMTs. We found that MAP65 was phosphorylated by a kinase which was coprecipitated with isolated CMTs, and CMTs of BY-2 cells became dispersed upon treatment with a kinase inhibitor, 6-DMAP. These results suggest that MAP65 regulates CMT organization through phosphorylation. To study the function of MAP65 in plant growth and differentiation, we investigated its expression in azuki bean epicotyl. In a 6 days old seedling. MAP65 was expressed entirely along the stem, but its content was significantly reduced in the basal region of 12 days old seedling. These results may suggest involvement of MAP65 in stem elongation.Interestingly, when epicotyl segments were incubated for 7days, MAP65 reappeared in the basal region. Immunoblot analysis and immunofluorescence microscopy revealed that the expression of MAP65 was intimately associated with adventitious root formation.