GSP-1 genes are linked to the grain hardness locus (Ha) on wheat chromosome 5D.

Abstract

An important determinant of wheat grain quality is the hardness of the grain. The trait is controlled by a major locus, Ha, on the short arm of chromosome 5D. Purified starch granules from soft-grained wheats have associated with them 15-kDa polypeptides called grain softness proteins (GSPs) or "friabilins." Genes that encode one family of closely related GSP polypeptides-GSP-1 genes-were mapped using chromosome substitution lines to the group 5 chromosomes. An F2 population segregating for hard and soft alleles at the Ha locus on a near-isogenic background was used in a single-seed study of the inheritance of grain softness and of GSP-1 alleles. Grain softness versus grain hardness was inherited in a 3:1 ratio. The wheat endosperm is a triploid tissue formed by fusion of two identical polar cells (from the female parent) with a sperm cell. The properties of the endosperm determine the end use of the wheat grain. Grain hardness or endosperm strength is one such important determinant of wheat end use. The mature wheat endosperm can be considered analogous to a polymer matrix (seed storage protein) in which a filler (starch granules) is dispersed (1). In such a structure, both the hardness of individual components and the degree of adhesion between them will determine overall strength (2). There is no detectable difference between hard and soft wheats in the individual hardness of starch granules or storage protein matrix fragments, but the degree of adhesion between starch granules and the surrounding protein matrix is higher in hard wheats (3-5). This higher adhesion results in both greater compressive strength and ductility for the endosperm as a whole (6, 7). Thus, in soft wheats, the main planes of weakness tend to occur at the starch-protein matrix interfaces and result in separation of the starch granules from the matrix with little damage during milling. As a result, starch granules from soft wheats take up less water when dough is formed and the product is more suited to the commercial production of cakes and biscuits than is dough from hard wheat flour [which is preferred for the baking of breads (8)].The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.Although there are various techniques for classifying grains as hard or soft, the phenotypic difference is largely controlled by one or two genetic loci (9, 10). The major gene (Ha) is on the short arm of chromosome 5D (11, 12). Morrison et al. (13,14) have shown that the Ha gene is tightly linked or identical to a gene controlling the level of extractable free polar lipids in the grain, Fpl-1. Genetic markers linked to milling energy in barley, which is analogous to grain hardness, were also recently shown to be located on the homologous chromosome 5H (15).The biochemistry that determines the hardness of the grain is not known. The linkage between Ha and Fpl-l suggests that lipid metabolism or...

Genetic and physical characterization of grain texture-related loci in diploid wheat

“…The loci Pina-D1 (Sourdille et al 1996) and Pinb-D1 (Giroux and Morris 1997) were previously mapped to the distal region of chromosome 5DS in dierent mapping populations. The grain softness-related gene Gsp-1 was also mapped on the same region of chromosome 5D of T. aestivum and Aegilops tauschii (Dubcovsky and Dvorak 1995;Jolly et al 1996) and chromosome 5A m of T. monococcum (Dubcovsky et al 1996). This indirect evidence for linkage among the three Ha-related genes was con®rmed here by demonstrating that these three genes are tightly linked in the distal region of the short arm of chromosome 5A m in a single segregating population.…”

“…cDNAs encoding for these proteins have been characterized (Gautier et al 1994;Rahman et al 1994) and mapped on the distal part of chromosome 5DS completely linked to the Ha locus. The Pina-1 and Pinb-1 loci have been detected only on the 5D chromosome but homoeologous Gsp-1 loci were detected on chromosomes 5A, 5B and 5D (Dubcovsky and Dvorak 1995;Jolly et al 1996;Sourdille et al 1996;Giroux and Morris 1997). Though linkage of puroindoline and Gsp-D1 genes to the Ha locus in dierent mapping populations suggests that these genes should be linked, no estimate is available of the genetic distances among these three genes because the limited polymorphism on the D genome of T. aestivum has precluded their study in a common mapping population.…”

Puroindoline allele diversity in Canadian and northern US hard spring wheat varieties differing in kernel hardness

“…result in high kernel hardness (Giroux et al 2000;Lillemo and Morris 2000;Morris et al 2001;Xia et al 2005;Chen et al 2006;Ram et al 2005). Grain softness proteins (GSPs) are closely related to puroindolines (Gautier et al 2000) and the grain softness protein-1 gene (Gsp-D1) is closely linked to the Ha locus in wheat (Jolly et al 1996) and T. monococcum L. (Gsp-Am1). Despite the close relationship among these three genes, there is no clear evidence of the role of Gsp-1 on grain kernel hardness (Tranquilli et al 2002).…”

Molecular characterization of diverse wheat germplasm for puroindolineproteins and their antimicrobial activity

“…Friabilin has been found on water-washed starch granules from soft wheat, while little or no friabilin has been found on water-washed starch granules from hard wheat (Greenwell and Scholfield, 1986). It was later shown that genes encoding friabilin were closely linked to the Ha locus on chromosome 5D (Jolly et al, 1996). N-terminal sequencing of friabilin revealed that it is composed mainly of 2 proteins, puroindoline A (PIN A) and puroindoline B (PIN B), which are the main components of friabilin (Jolly et al, 1993;Morris et al, 1994).…”