CHANGES IN THE ACCUMULATION OF ALPHA-TUBULIN AND BETA-TUBULIN ISOTYPES DURING COTTON FIBER DEVELOPMENT

The expression of alpha- and beta-tubulin proteins in developing fiber s and several other tissues of cotton (Gossypium hirsutum, cv Texas Ma rker 1) have been analyzed by immunoblots of one- and two-dimensional gels utilizing anti-tubulin antibodies as probes. As a percentage of t otal protein, fibers had greater amounts of tubulin than did hypocotyl s, roots, leaves, or cotyledons. Both alpha- and beta-tubulin, having apparent molecular masses of approximately 50 kD and isoelectric point s between pH 5 and pH 6, were resolved on a single two-dimensional gel . Under the conditions used, alpha-tubulin was less acidic in the isoe lectric focusing dimension and migrated slightly faster in the sodium dodecyl sulfate dimension than did beta-tubulin. Nine alpha-tubulin is otypes that formed two distinct groups were identified on immunoblots of two-dimensional gels. The three most abundant alpha-tubulin isotype s were common to all tissues examined. Seven distinct beta-tubulin iso types were also identified. Although their level of accumulation diffe red, four of the beta-tubulin isotypes were common to all tissues. Pre ferential accumulation of isotypes was more apparent in fibers than in the other tissues examined. Two alpha-tubulin isotypes and two beta-t ubulin isotypes showed preferential accumulation in 10- and 20-d posta nthesis fibers, respectively.