Physical interaction of native and mutated forms of puroindolines shown using the yeast two hybrid system

Grain hardness is an important trait·used in the classification of wheat and in determining its end use. Two major components of a protein group associated with the surface of starch granules, puroindoline a (PINA) and puroindoline b (p1NB), have been to shown to significantly influence grain hardness. Common wheats that have both puroindolines present in their wild form are soft textured, while the various hard kernel phenotypes have mutation or deletion in either PINs. The extremely hard durum wheat lacks these proteins. The primary role for these lipid binding proteins is most likely antimicrobial, as demonstrated in previous in-vitro and in-vivo studies (Bhave and Moms, 2008). Several reports on transcripts and protein level comparison as well as transgenic work, have shown that the lipid binding properties of PINs require some co-operation or interdependence (Capparelli et ai, 2003; Amoroso et al, 2004; Hogg et aI, 2004; Swan et aI, 2006). An understanding of the interaetions between these proteins would help elucidate their biological function in grain texture and possible antimicrobial applications. In this study, the yeast two hybrid system was used to study physical interactions between PINA and PINB from two soft common wheats and a Pinh-D1b wheat type