Variability among members of the Hor-2 multigene family.

The hordeins comprise the major prolamin storage proteins of barley. Two major and one minor gene families encode these alcohol-soluble proteins. The Hor-2 gene family encoding the B-hordeins has been estimated to contain 15-30 copies. Although several genes encoding B-hordeins have been cloned and sequenced, little is known about the mechanisms responsible for the generation of the enormous genetic variability at this locus. Polymerase chain reaction sequence amplification provided a simple technique that permitted the amplification of the Hor-2 gene family members from the genomes of several barley genotypes. Sequence analysis of clones permitted the identification of a region within the Hor-2 structural gene that appears to undergo recombinational and slippage-like gene conversion events. In this report we describe variability of the B-hordein genes, possible mechanisms responsible for it, and implications this may have on the evolution of prolamin-encoding gene families.