The Structure Characters Of The Gene Of Gx-type HMW-GS In Triticum Araraticum

The high-molecular-weight glutenin subunit (HMW-GS) of Triticeae species is one of the most important storage proteins. The HMW-GS plays an important role in determining the quality of wheat flour. There is still no reported the Gx-type HMW-GS in Triticum araraticum Jakubz. (2n=4x=28, AAGG). In this study, the Gx gene cloning, sequencing analysis, and sequence alignment of T. araraticum from Azerbaijan were carried out. The results as follows:1. Separation and identification of the GxPCR for the genomic DNA from T. araraticum (PI427305) was conducted by using a pair of HWM-GS primers (PF,PR), The size of the amplified fragments is about 2.5 kb. The PCR fragment was inserted into the PMD18-T vector, and then sequenced using overlapping sub-clones. It was compared by using BLAST in NCBI, The DNA sequnces showed the highest homology with that of Bx in Triticum aestivum L. Therefore, The result proved it to be the gene of Gx, and the GenBank number is HM116373.2. Gx gene from T. araraticumThe coding sequence began with ATG start codon and ended with double stop codon TGATAG, encoded 855 amino acid residues. The deduced ami no acid sequence had the typical structure of x-type HMW-GS including a signal peptide with 21 amino acid residues, non-repetitive N-terminal domain with 87 amino acid residues (3 Cys), non-repetitive C-terminal domain with 42 amino acid residues (1 Cys) and central repetitive domain with 441 amino acid residues. The repetitive domain is imbued with polypeptide, including tripep-tide, hexapeptide, nonapeptide, undecapeptide, 12-merpeptide, and rare pentapeptide. in which, hexapeptide was the most, reaching up to 67.59%.3. The comparison of amino acids in mature proteinSeveral kinds of x-type subunits in Triticeae from the four different genome A,B,D and G were compared. The results proclaim that the AA components and the contents of Gx from T. araraticum is high similar to others x-type subunits from genome B. The compared x-type subunits possessed glutamine (Gln) being highest, glycine (Gly) and proline (Pro) higher compared with other amino acids. The three types of amino acids mainly existed in the hexapeptide PGQGQQ which existed in amino acid sequences at highest frequency. Meanwhile, three kind of amino acids in the total content of these amino acids are the same, the three of them are His, Phe and Met. From the constrast of Repeat region, the composition and distribution of Gx repeat region peptide subunit are more similar to the x-type subunits form genome B.4. Homology analysis of GxBoth N-and C-terminal amino acid sequences were used to build a dendrogram of Gx with other kinds of HMW glutenin subunits including seven x-types from genome B in Triticum and four x-types from genome D, and two x-tyoes from genome A. It was obtained that all the 15 subunits were divided into two big categories. One contains genome A and D, the other including B and G. The Gx was classified together with genome B, and the reliability is over 90%. All results revealed that the Gx subunit have an obvious genetic similarity with the Bx-types HMW subunit.