α-Tubulin genes are differentially expressed during leaf cell development in barley (Hordeum vulgare L.)

Intricate changes in the patterns of the cytoskeleton, especially of microtubules, appear to control the establishment of complex plant cell shapes. Little is known about how these changes are accomplished. The objective of the present study was to test whether or not alpha -tubulin genes are differentially expressed during cell shaping in growing leaves of barley (Hordeum vulgare L.). Five alpha -tubulin genes representing at least most members of the gene family were found to be expressed in the leaf. Dot-blot analyses revealed expression patterns that could be classified into three groups. Two isotypes (HVATUB2 and HVATUB4) were maximally expressed in the meristem with a steady decline during the differentiation process (1). One isotype (HVATUB3) appeared to be constitutively expressed during cell shaping, although strongest signals were found during late stages, before the general decline in microtubular activity (2). The most striking finding was that two types (HVATUB1 and HVATUB5) were almost exclusively expressed in early post-mitotic cells, when transverse microtubular bundles determining the future cell shape in the mesophyll are formed (3). Relative transcript abundance was highest in HVATUB2 and HVATUB3, whereas the transcript level of the only transiently expressed HVATUB5 was very low, even during its phase of maximum expression. The results are discussed in the context of the general debate relating to the significance of multiple tubulin isotypes.