Reference "Evolution and heterogeneity of the alpha-/beta-type and gamma-type gliadin DNA sequences"

Reference ID

9108

Title

Evolution and heterogeneity of the alpha-/beta-type and gamma-type gliadin DNA sequences

Source

The Journal of biological chemistry, 1985, vol. 260, pp. 8203-8213

Authors (3)

Okita-T-W	Cheesbrough-V
Reeves-C-D

Abstract

Near full length cDNA clones for both alpha-/beta- and gamma-type gliadins were
isolated and studied for sequence diversity. Based on restriction site
polymorphism and cross-hybridization studies, alpha-/beta- and gamma-type clones
could be divided into five and three homology classes, respectively. Clones
representing each of the different classes were sequenced and compared. Sequence
divergence between the classes was due to single-base substitutions and to
duplications or deletions within or near direct repeats. Thus, through numerous
duplications and subsequent divergence, the gliadin multigene family encodes a
polymorphic set of polypeptides differing in both isoelectric point and
molecular size. Southern blot analysis of wheat DNA suggested that the number of
genes encoding the alpha-/beta-type gliadins was extremely large (greater than
100 copies/haploid genome). Inasmuch as hybridization patterns were the same
using DNA isolated from seeds or leaves, amplification or rearrangement of DNA
does not occur during development. The complete coding sequence of a gamma-
gliadin was similar to that observed for the alpha-/beta-gliadins, but with
several notable differences. Comparison of gamma-type gliadin cDNA sequences
showed that, unlike the conserved dodecamer repeat common to all the alpha-/beta-
gliadins, the tandem repeat unit differed among gamma-gliadin clones.