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

Abstract

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 alpha-tubulin. Thus, 'P 115.1' apparently represents an embryo sac-specific isoform of alpha-tubulin involved in the initiation of embryo development.

Molecular control of autonomous embryo and endosperm development

“…Importantly, cultivated Salmon-wheat egg cells can develop autonomously into parthenogenetic embryos (Kumlehn et al 2001), illustrating that no external signals are required and that all factors required for egg activation are present in the quiescent egg cell. While the exact cellular events that lead to egg activation and embryogenesis in Salmon wheat are not known, the system offers a unique opportunity to analyze the first steps of parthenogenesis at the molecular level (Balzer et al 1996;Matzk et al 1995Matzk et al , 1997Matzk et al , 2007.…”