Creation and functional analysis of new Puroindoline alleles in Triticum aestivum

The Hardness (Ha) locus controls grain texture and affects many end-use properties of wheat (Triticum aestivum L.). The Ha locus is functionally comprised of the Puroindoline a and b genes, Pina and Pinb, respectively. The lack of Pin allelic diversity is a major factor limiting Ha functional analyses and wheat quality improvement. In order to create new Ha alleles, a 630 member M(2) population was produced in the soft white spring cultivar Alpowa using ethylmethane sulfonate mutagenesis. The M(2) population was screened to identify new alleles of Pina and Pinb. Eighteen new Pin alleles, including eight missense alleles, were identified. F(2) populations for four of the new Pin alleles were developed after crossing each back to non-mutant Alpowa. Grain hardness was then measured on F(2:3) seeds and the impact of each allele on grain hardness was quantified. The tested mutations were responsible for between 28 and 94% of the grain hardness variation and seed weight and vigor of all mutation lines was restored among the F(2) populations. Selection of new Pin alleles following direct phenotyping or direct sequencing is a successful approach to identify new Ha alleles useful in improving wheat product quality and understanding Ha locus function.

Molecular genetics of puroindolines and related genes: regulation of expression, membrane binding properties and applications

Kernel texture of wheat is a primary determinant of its technological properties. Soft kernel texture phenotype results when the Puroindoline a and Puroindoline b genes are present and encode the wild-type puroindolines PINA and PINB, respectively, and various mutations in either or both gene(s) result in hard phenotypes. A wealth of information is now available that furthers our understanding regarding the spatial and temporal regulation of expression of Puroindoline genes. Through the use of model membranes and synthetic peptides we also have a clearer understanding of the significance of the cysteine backbone, the tryptophan-rich domain (TRD) and the helicoid tertiary structures of PIN proteins in relation to their membrane-active properties. Many studies suggest individual yet co-operative modes of action of the PIN proteins in determining kernel texture, and significant evidence is accumulating that the proteins have in vivo and in vitro antimicrobial activities, shedding light on the biological roles of this unique ensemble of proteins. The puroindolines are now being explored for grain kernel texture modifications as well as antimicrobial activities.