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