Characterization of HMW prolamines and their coding sequences from Crithopsis delileana

摘要

The high molecular weight (HMW) glutenins are conserved storage proteins, which are particularly important for determining wheat gluten and dough elasticity (Payne 1987; Shewry et al. 1992, 1995). In hexaploid wheat, HMW glutenin genes are encoded by three loci, Glu-1A, Glu-1B and Glu-1D, located on the long arms of the homologous group one chromosomes, respectively (Payne and Lawrence 1983; Anderson et al. 1989). It was found that each Glu-1 locus consist of two tightly linked genes encoding for an x-type and a y-type subunit (Payne 1987). Generally, the primary structures of amino acid sequences of HMW glutenin subunits consist of four regions, a signal peptide and a repetitive central domain that predominantly consists of repeats coding for tri-, hexa- and nona-peptides flanking by two highly conserved terminal domains N and C. Within the N- and C-terminal regions, there are a few cysteine residues that are highly conserved in both number and positions (Shewry et al. 1995). The differences in the number of repeats are the main reasons for allelic variation. Due to the presence of several cysteines in both the N- and C-terminal regions of HMW gluten peptides, the visco-elastic properties of bread flour have been associated with the formation of disulfide bridge-linked aggregates (Shewry et al. 1992).Evolutionary studies have indicated the common origin of the prolamin genes in the tribe of Triticeae species (Kreis et al. 1985), and the wild species belonging to this tribe have been widely used as a source for novel prolamin investigations. Therefore, the characterization of HMW glutenins in wheat related species could offer precious information for better understanding quality associated subunits, and for studying the evolutionary relationship of HMW glutenin. Now, the HMW glutenin subunits in many wheat related species had been characterized, such as barley, rye, Aegilops, Elytrigia elongata etc. (Lawrence and Shepherd 1981; Halford et al. 1992b; Bustos et al. 2001, Bustos and Jouve 2003; Yan et al. 2002; Liu et al. 2003; Wang et al. 2004).Crithopsis delileana (Schult) Roshev (2n=2x=14, KK) is the only member of the genus Crithopsis Jaub. Et Spach. in the Triticeae group. The distribution of C. delileana extends from northern of Africa to the southwest of Asia (Sakamoto 1973; L?ve 1984; Frederiksen 1993). Intergeneric hybridization between Crithopsis and other members of the Triticeae was difficult (Sakamoto 1973; Frederiksen and Bothmer 1989). The classification and evolution about this species has been obtained by using morphology, cytology and molecular biology methods (Hsiao et al. 1995; Catalan et al. 1997; Petersen and Seberg 1997; Linde-Laursen et al. 1999). However, the phylogenetic relationships between this species and the other species in Triticeae have not been comprehensively established.