The hardness (or texture) of the wheat grain is a primary determinant of its technological qualities. Much of the variation in grain texture of wheat is controlled by the gene Puroindoline a and Puroindoline b (Pina-Dl and Pinb-Dl) located at the Ha locus on short arm of chromosome 5D. The genes encode PINA and PINB proteins, which are small (-13 kDa; 148 amino acids), cysteine-rich, basic (estimated pi 8.76, 9.13 for PINA and PINB mature proteins, respectively) and share significant identity (60%),including certain key residues and domains. The proteins interact with lipids and are associated as the protein mixture 'friabilin' (comprised of the major components PINA and PINB and the minor protein GSP-1, encoded by the third gene Gsp-1 at the Ha locus) with the surface of starch isolated from soft but not hard wheats. A great diversity of alleles of both Pin genes is now known from bread wheat, its diploid progenitors and synthetic wheats. The Pin homologues in diploid progenitors, other Triticeaegrasses and synthetic wheats and orthologues in rye and barley are also being investigated in order to understand the evolution of this gene family and find potentially useful variants. The discovery and properties of friabilin have been reviewed previously (Morris 2002) and the Pin allele diversity and the expression and regulation of Pin genes reviewed recently (Bhave and Morris 2008a, b). All allelic sequences and their sources are analysed, the duplications and discrepancies clarified and allele designations updated in Morris and Bhave (2008). This report updates the allele diversity and reports further developments based on the biochemical genetics of puroindolines.
展开▼
