A Specific α-Tubulin is Associated with the Initiation of Parthenogenesis in 'Salmon' Wheat Lines

The ‘Salmon system’ consists of isogenic but alloplasmic wheat lines with either sexual or autonomous embryo development. Using two‐dimensional gel electrophoresis these lines have been screened for proteins potentially involved in the initiation of parthenogenesis. A temporally altered expression of the polypeptide ‘P 115.1’ in the sexual and parthenogenetic ‘Salmon’ lines seems to be related with the autonomous embryo formation. Around anthesis when most of the egg cells begin the parthenogenetic development, the polypeptide ‘P 115.1’ was present in ovaries of the parthenogenetic lines but not in ovaries of the sexual line. Moreover, this polypeptide is only expressed in the ovaries of amphidiploid 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 polypeptide was neither detectable in meristematic tissue of root tips nor in leaves. N‐terminal amino acid sequencing identified ‘P 115.1’ as an α‐tubulin. Thus, ‘P 115.1’ apparently represents an embryo sac‐specific isoform of α‐tubulin involved in the initiation of embryo development.