Hereditas 126: 219-224 (1997) zyxwvuts A specific a-tubulin is associated with the initiation of parthenogenesis in ‘Salmon’ wheat lines FRITZ MATZK, HANS-MARTIN MEYER, CHRISTIAN HORSTMANN, HANS-JORG BALZER, HELMUT BAUMLEIN and INGO SCHUBERT Institut fur Pflunzengenetik und Kulturpjlanzenforschung zyxwvu (IPK), Gatersleben, Germany Matzk, F., Meyer, H.-M., Hortmann, C., Balzer, H.-J., Baumlein, H. and Schubert, zyxwv 1. 1997. A specific cr-tubulin is associated with the initiation of Parthenogenesis in ‘Salmon’ wheat lines. zyxwvut ~ Hereditas 126 219-224. Lund, Sweden. ISSN 0018-0661. Received April 1, 1997. Accepted May 12, 1997 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 u-tubulin. Thus, zyxwvutsrq ‘P 115. I’ apparently represents an embryo sac-specific isoform of u-tubulin involved in the initiation of embryo development. Fritz Matrk, Instirut zyxwvutsrqponm ,fur Pflan:engenrtik und Kulrurpflanzenjorschung, Corrensstrasse 3, 0-06466 Gatersleben, Germany The structural changes within the embryo sacs of cereals during the beginning of embryo development were studied intensively by light and electron mi- croscopy (You and JENSEN 1985; HAUSE 1991; GAO et al. 1992; ENGELL 1994; TAYLOR and VASIL 1995). However, m,olecular events responsible for the alter- nation from the gametophyte to the sporophyte in the life cycle of higher plants are unknown. There is still a lack of information concerning those genes and their products that trigger the initiation of embryo development in vivo. Recently, micropreparation of the female gameto- phytes has been established for molecular studies in gramineous species (DUMAS and RUSSELL 1992; NAUMOVA et al. 1993; MOGENSEN et al. 1995; MOURITZEN and HOLM 1995; DRESSELHAUS et al. 1996). These procedures are laborious and time-con- suming, and it takes quite some effort to prepare embryo sacs or egg cells in sufficient quantity for the analysis of temporal and spatial expression patterns of genes that are active before or at the beginning of embryogenesis. Here we demonstrate a much easier way to deter- mine gene expression associated with megagameto- phytes. It is based on our observation that haploid plants lack any embryo sac structure within the ovules while ovaries of diploid plants contain mature embryo sacs. For that reason, the comparison of the patterns of proteins extracted from entire ovaries of diploid and corresponding haploid plants should re- veal the gene products which are expressed only in the presence of megagametophytes. One polypeptide apparently involved in the initiation of parthenogene- sis in the ‘Salmon system’ of wheat (MATZKet al. 1995), was tested by this approach. The protein iden- tified as or-tubulin was present only in ovary extracts of diploid plants. The ‘Salmon system’ characterized by isogenic sexual and parthenogenetic lines offers a suitable model to study the initiation of embryo development in vivo and to generate apomixis (MATZK et al. 1995; MATZK1996). MATERIALS AND METHODS The so-called ‘Salmon system’ of wheat consists of the sexual line ‘(uestivum)-Salmon’ (as), and the two alloplasmic parthenogenetic lines ‘(cuudutu)-Salmon’ (cS) and ‘(kotschyi)-Salmon’ (kS). The details of the lines were already described (MATZK et al. 1995; MATZK 1996). For screening of parthenogenesis-specific proteins by means of 2-dimensional electrophoresis (see MATZKet al. 1995), ovaries of amphidiploid plants of the three isogenic lines were dissected at different developmental stages between sporogenesis and an- thesis as well as after anthesis. Samples of 150 mg of ovaries of each stage were used (correspondingly about 240 ovaries three days after meiosis or 40 ovaries during anthesis). The developmental stages were defined in relation to the first meiotic division of pollen mother cells, which was detected by mi- croscopy investigations. To test for embryo sac-