A SPECIFIC ALPHA-TUBULIN IS ASSOCIATED WITH THE INITIATION OF PARTHENOGENESIS IN SALMON WHEAT LINES

The 'Salmon system' consists of isogenic but alloplasmic wheat lines w ith either sexual or autonomous embryo development. Using two-dimensio nal gel electrophoresis these lines have been screened for proteins po tentially involved in the initiation of parthenogenesis. A temporally altered expression of the polypeptide 'P 115.1' in the sexual and part henogenetic 'Salmon' lines seems to be related with the autonomous emb ryo formation. Around anthesis when most of the egg cells begin the pa rthenogenetic development, the polypeptide 'P 115.1' was present in ov aries of the parthenogenetic lines but not in ovaries of the sexual li ne. Moreover, this polypeptide is only expressed in the ovaries of amp hidiploid parthenogenetic plants containing differentiated embryo sacs . It is absent from ovaries of the analogous polyhaploid plants, which lack any embryo sac structure within their ovules. Furthermore, the p olypeptide was neither detectable in meristematic tissue of root tips nor in leaves. N-terminal amino acid sequencing identified 'P 115.1' a s an alpha-tubulin. Thus, 'P 115.1' apparently represents an embryo sa c-specific isoform of alpha-tubulin involved in the initiation of embr yo development.