Characterization of a 100‐kDa heat‐stable microtubule‐associated protein from higher plants

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Abstract
In higher‐plant cells, the different cell‐cycle‐dependent microtubule arrays are involved in a wide range of activities including chromosome segregation, cell‐plate formation and cellulose microfibril distribution and orientation. A wealth of data, obtained using animal cells, has indicated that the differential stability and function of microtubules during cell‐cycle and/or differentiation could be primarily regulated by selective microtubule‐associated proteins (MAP). Compared to animal MAP, our knowledge of plant MAP is so far very limited. In this study, we have identified a maize heat‐stable protein with apparent molecular mass 100 kDa (P‐100) which binds to taxol‐stabilized neurotubules and copolymerizes in vitro with purified neural tubulin. Moreover, P‐100 cross‐reacts with affinity‐purified · antibodies like a maize 83‐kDa putative MAP described previously [Vantard, M., Schellenbaum, P., Fellous, A. & Lambert, A. M. (1991) Biochemistry 30, 9334–9340]. Polyclonal antibodies directed against P‐100 were obtained and indicated that this protein is found in diverse higher‐plant cultured cells suggesting the ubiquitous nature of this protein. P‐100 can be phosphorylated in vitro by protein kinases present in a maize cytosol extract. Together, our data suggest that P‐100 could be a higher plant MAP.

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