Identification of novel serpin isoforms and serpin polymorphisms among Australian wheat cultivars

Serpins constitute a large family of related proteins, the majority of which are serine protease inhibitors (from which their name is derived). They are known to be abundantly and polymorphically expressed in individual wheat cultivars. However, to date there lacks a detailed investigation into their inter-genotypic polymorphisms in larger wheat collections. In this study, a systematic proteomic approach, combining native polyacrylamide gel electrophoresis (PAGE), SDS-PAGE, two-dimensional gel electrophoresis, tandem mass spectrometry (MS/MS) and immunoblotting, was taken to characterize serpin polymorphisms among 177 Australian and 19 foreign hexaploid as well as 6 tetraploid wheat varieties. A total of seven serpin isoforms were identified and five unique expression patterns of these serpins were clearly revealed among varieties. In particular, the novel serpin isoforms 3a and 3b were highly polymorphic in the collection of wheat cultivars and are structurally diverse from the other serpin isoforms. The findings and methodology established in this study are not only immediately applicable in wheat breeding and varietal differentiation but may also be useful for delineation of serpin function in bread or pasta making in the future.