TUBULIN ISOTYPES IN MAIZE ENDOSPERM - ALTERATIONS DURING DEVELOPMENT AND WATER-DEFICIT

Maize (Zea mays L. cv. Pioneer 3925) endosperm development is sensitiv e to water deficit during rapid cell division and nuclear DNA endoredu plication. To gain insight into effects of water deficit on gene-produ cts that are involved in these processes, we examined the accumulation of beta-tubulin, a 50-kDa subunit of microtubules. Proteins extracted from endosperms were separated by SDS-PAGE and immunoblotted with ant ibodies to beta-tubulin. In addition to the expected 50-kDa beta-tubul in protein, monoclonal antibodies recognized a 35-kDa protein that pre dominated at early stages of development and progressively disappeared coincident with the appearance of 50-kDa beta-tubulin. Various tests demonstrated that the cross-reacting 35-kDa protein was not a post-har vest artifact, but represented a group of in situ tubulin isotypes pre ferentially detected by the monoclonal antibodies we used. The pattern of appearance of the fragment suggested that differential expression or degradation of tubulin isotypes normally occurs during development. This expression pattern is prolonged or altered during water deficit, which may affect cell division.