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 fibers and several other tissues of cotton (Gossypium hirsutum, cv Texas Marker 1) have been analyzed by immunoblots of one- and two-dimensional gels utilizing anti-tubulin antibodies as probes. As a percentage of total protein, fibers had greater amounts of tubulin than did hypocotyls, roots, leaves, or cotyledons. Both alpha- and beta-tubulin, having apparent molecular masses of approximately 50 kD and isoelectric points 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 isoelectric focusing dimension and migrated slightly faster in the sodium dodecyl sulfate dimension than did beta-tubulin. Nine alpha-tubulin isotypes that formed two distinct groups were identified on immunoblots of two-dimensional gels. The three most abundant alpha-tubulin isotypes were common to all tissues examined. Seven distinct beta-tubulin isotypes were also identified. Although their level of accumulation differed, four of the beta-tubulin isotypes were common to all tissues. Preferential accumulation of isotypes was more apparent in fibers than in the other tissues examined. Two alpha-tubulin isotypes and two beta-tubulin isotypes showed preferential accumulation in 10- and 20-d postanthesis fibers, respectively.