Study On LMW Glutenin Gene Family In Tetraploid Wheat

Low-molecular-weight glutenin subunits (LMW-GS) are a major fraction of wheat glutenin and account for 60% of the glutenins. They play an important role in determining the processing properties of wheat. The LMW-GS are encoded by Glu-A3, Glu-B3 and Glu-D3 on the short arm of chromosome 1A, 1B and 1D. They are present as a multigene family in close association with gliadin. This may lead to the difficulty in studying LMW-GS. With the goal to understand the members of LMW-GS gene family, their location and evolution clearly, Langdon BAC clones from preliminary screening with the Glu-3 coding region as a probe were amplified with conservative primers. Their PCR products were cloned, sequenced and analyzed. Two validated BAC clones were selected to do shotgun sequencing and analysis. The results were as follows:1. With conservative primers, 26 complete gene sequences were obtained by PCR from the 92 BAC clones. With deduced amino acid sequences, they were divided into three types; including 9 i-type, 11 s-type and 6 m-type genes. Phylogenetic tree of nucleotide sequence of this 26 LMW-GS genes showed that they were divided into 5 groups.2. Five pair specific primers were developed based on SNP between different group sequences. These primers can be used to not only identify different type of LMW-GS genes, but also map the genes onto 1A or 1B chromosome using T. durum cv Langdon and its substitution line, Chinese Spring and its nulli-tetrasomic lines.3. Two representative BAC clones were selected to do shotgun sequencing and analysis. BAC459F23 was 173kb. This BAC contained CACTA, gypsy, copia, LINE and other repetitive sequences. It also carried pseudo LMW-GS gene, two powdery mildew resistance gene fragments, RFLP marker SFR159 fragment and some other unknown gene fragments. BAC817O07 was about 103kb. It contained CACTA, MITE, gypsy and other repetitive sequences. It also carried one expressed LMW-GS gene, HBP-1a transcription factor and RFLP marker SFR159 segment. Microcolinearity at Glu-3 loci with different BAC clones in Langdon was revealed. The sequences of SFR159 had high comparability in BAC459F23, BAC817O07, BAC 419P13 and BAC 107G22. The sequence between LMW-GS gene and SFR159 also had high comparability in BAC459F23 and BAC817O07. Therefore, BAC 459F23 and BAC817O07 could be having a close position on chromosome.