Isolation and characterisation of friabilin genes in rye

The Hardness locus on chromosome 5D is the main determinant of grain texture in hexaploid wheat. Puroindoline-a (pin-a), puroindoline-b (pin-b) and Grain Softness Protein (GSP) genes are tightly linked at this locus and their products are the predominant components of friabilin, a 15 kDa endosperm protein complex. Differences in grain texture are mainly caused by specific puroindoline genes mutations and are known to play a large impact on the end-product quality of wheat, contributing to the distinction of well-suited market classes for specific end-uses. We investigated friabilin genes in rye (Secale cereale L.), aiming at an increase information on the friabilin molecular system in cereals and to further investigate their potential use for the genetic improvement of this crop. Using a PCR approach, puroindoline-b and GSP-like sequences were identified for the first time in several rye and triticale cultivars, sequenced and located on specific chromosomal arms. The primary structures of deduced proteins were determined and compared with those from other cereal species. In contrast with data from previous studies, secaloindoline-a was not found. Our results introduce new evidence for a discrete allelic variation at the secaloindoline loci in rye, indicating that future larger screenings may facilitate preliminary selection of germplasm for rye breeding purposes and triticale production.