Characterization of a wheat gene coding for polyglutamine and the chromosomal locations of selected storage protein genes

pBSLM21, selected from a wheat Eco RI genomic library in Charon 32 (Murray et al. 1984), consists of what appears to be a gene which encodes a 156-residue polypeptide. This gene contains an unusual CAA/CAG-rich region of 834 nucleotides. Also present in the open reading frame are premature stop codons which, if read through in vivo would yield a 334-residue polypeptide. pBSLM21 contains the typical transcriptional and translational elements with a few minor differences. The TATA box is TATAGG instead of the typical TATAAA and its location is -130 instead of the normal -90 to -110 location observed in eukaryotic genes. Northern blot analysis showed that this gene is expressed in wheat endosperm and is neither expressed in barley endosperm nor barley aleurone layer. The polypeptide which is encoded by pBSLM21 has a very unusual amino acid composition in that over 80% of it is glutamine. The first twenty amino acids are rather hydrophobic which could signify a signal peptide.;Restriction fragment-linked polymorphism studies, using nullisomic-tetrasomic and ditelosomic 'Chinese Spring' lines, were carried in order to determine the genomic and chromosomal locations of various storage protein genes. Three probes, pW4, pW8233, and pW1215, for alpha/beta gliadin hybridized to two Hind III fragments, a 2.4 kb and a 4.6 kb bands, which are located on the short arm of chromosome 6B. A 3 kb band is located on all three of the genomes.;The use of probes made from the coding region of MABSPH, a gamma gliadin gene, showed 12 hybridizing Hind III fragments ranging in size from 1.9 to 20 kb. All but two (2 kb and 8 kb) of these bands could be assigned to specific genomes. A 1.9 kb and a 9 kb bands are A genome specific. Four of the bands (2.4, 4.9, 5.3, 7.9, and 20 kb) are specific for the B genome. Three bands, 2.8, 4.4, and 6.7 kb, are specific for the D genome. The use of the upstream region indicated that only the 2.4 kb Hind III fragment contain a gene with sequence similarity with that of MABSPH.;The use of L4.9, another gamma gliadin gene probe, showed a single hybridizing Hind III or Bam HI fragment of 3 kb which seemed to be present on all three of the genomes. 15R, a probe for LMW glutenin subunit genes showed a single hybridizing band of 8 kb which is located on all three of the genomes as well.