Molecular genetics of puroindolines and related genes: allelic diversity in wheat and other grasses

Abstract

The hardness or texture of cereal grains is a primary determinant of their technological and processing quality. Among members of the Triticeae, most notably wheat, much of the variation in texture is controlled by a single locus comprised of the Puroindoline a, Puroindoline b and Grain Softness Protein-1 (Gsp-1) genes. Puroindolines confer the three major texture classes of soft and hard common wheat and the very hard durum wheat. The protein products of these genes interact with lipids and are associated with the surface of isolated starch (as a protein fraction known as 'friabilin'). During the past ten years a great diversity of alleles of both Puroindoline genes have been discovered and significant advances made in understanding the relationship between the gene presence/absence, sequence polymorphism and texture of cereal grains. Efforts have also focussed on Puroindoline and Gsp-1 genes in diploid progenitors, other Triticeae grasses and synthetic wheats in order to understand the evolution of this gene family and find potentially useful variants. The puroindoline homologues in other cereals such as rye and barley are also receiving attention. This work summarises new developments in molecular genetics of puroindolines in wheat and related Triticeae grasses, and the related genes in other cereals.

In Planta Mutagenesis Determines the Functional Regions of the Wheat Puroindoline Proteins

“…Apart from mutations affecting cysteines, all other functionabolishing mutations were centered on the Trp-rich domain, indicating that this region is the most important for PIN function. Many PINA and PINB missense mutations naturally present in hard wheats are also centered on this domain (reviewed in Bhave and Morris 2008). Two such PINB missense alleles (PINBG75S and PINBW73R) were shown to negatively affect the degree to which PINB could penetrate lipid layers (Clifton et al 2007a,b;.…”

A Puroindoline Mutigene Family Exhibits Sequence Diversity in Wheat and is Associated with Yield-Related Traits

“…The expression of puroindoline genes is mainly associated with 'soft' and 'hard' grain texture of bread wheat, whereas durum wheat is 'very hard' due to the lack of puroindoline genes (Capparelli et al 2003). Extensive genetic surveys, cytological analysis, and transformation experiments in wheat and rice (Oryza sativa) have demonstrated that puroindoline a and b act to create soft kernel texture (Bhave and Morris 2008a, b, Morris 2002, Morris and Bhave 2008. However, puroindolines have also been extensively studied regarding their multiple roles in the development and resistance of plants against biotic stress, and their profound influence on the breeding and processing quality of food crops (Luo et al 2008;Morris 1997, 1998;Ragupathy and Cloutier 2008;Chen et al 2007a, b).…”

Analysis of Pina and Pinb alleles in the micro-core collections of Chinese wheat germplasm by Ecotilling and identification of a novel Pinb allele

“…Soft wheat varieties possess wild type (WT) forms of both Pin proteins (Bhave and Morris, 2008a). In contrast, hard wheat varieties display mutations in one or both Pin genes, which lead to changes in Pin protein structure and/or expression pattern (Bhave and Morris, 2008b).…”