Chromosomal location of seed storage protein genes in the genome of Elytrigia elongata

Abstract

Additions of complete and telocentric chromosomes of Elytrigia elongata (Host) Nevski in Triticum aestivum L. 'Chinese Spring' were employed to assign the genes coding for seed storage proteins to chromosome arms in the E. elongata genome. Genes coding for prolamins equivalent to wheat gliadins were found on chromosome arms 1ES and 6Ep. Genes on chromosome arm 1ES, which is presumably the p arm, coded for several components with electrophoretic mobilities (lactate–PAGE) corresponding to those of β-, γ-, and ω- gliadins and those on chromosome arm 6Ep coded for two components with mobilities corresponding to those of β-gliadins. Amino acid sequencing of mixtures of prolamins from E. elongata and from E. pontica (Podp.) Holub, a species closely related to E. elongata, indicated that prolamins of these species correspond to α-type (which includes β-gliadins), γ-type, and ω-type gliadins. Restriction fragments of genomic DNAs from substitution lines of chromosome 6E of E. elongata in 'Chinese Spring' were separated electrophoretically in agarose gels and probed with a cloned α-type gliadin gene from 'Yamhill'. This Southern blot showed that chromosome 6E yields DNA fragments identical in size to those characteristic of the α-gliadin gene cluster that is on chromosome 6A of 'Chinese Spring', 'Cheyenne', and 'Yamhill'. These results indicate that structural genes for prolamins of Elytrigia are similar to those of wheat gliadins and are located on the same chromosome arms as those in Triticum species. A high molecular weight (HMW) protein likely to be a HMW glutenin subunit was located on the long arm of chromosome 1E, which presumably is the q arm; this also is in accordance with the location of HMW glutenin subunit genes in Triticum. It is concluded that the appearance of α-type gliadin genes on chromosomes of homoeologous group 6 in T. aestivum occurred prior to divergence of Triticum and Elytrigia but after the divergence of Secale, Hordeum, and the Triticum–Elytrigia lineages, since neither Secale or Hordeum appear to have α-type genes. It is, however, possible that α-type gliadin genes were deleted from the ancestors of Secale and Hordeum after divergence from the Triticum–Elytrigia lineage.Key words: Elytrigia elongata, gene location, prolamins, gliadins, wheat.