Cloning And Molecular Characterization Of LMW Glutenin Subunit Genes In Triticum Dicoccoides

Glutenin is important component of wheat seed storage proteins and play the major role indetermining bread-making quality. The low molecular weight glutenin subunits(LMW-GS) account for40%of gross glutenins of wheat, had great effects on dough extensibility and food processing quality andusually used as major indicator for wheat quality improvement. Triticum dicoccoides(AABB) is the donorancestor species of T.aestivum(AABBDD). It was found to possess high protein content(20%-40%)andextensive glutenin variation, therefore it is expected to serve as an important gene resource for bread wheatquality improvement. In this study, A pair of allele specific PCR primers was used to amplify and clonesome LMW-GS genes from T. dicoccoides J129. The main results were as follows:(1) Total10(named as LMWTD-1～LMWTD-10) LMW-GS genes were amplified and cloned from T.dicoccoides J129, including four (LMWTD-1～LMWTD-4) novel full-ORF which could respectivelycoding294、307、301and294amino acid residues and the remaining sequences (LMWTD-5～LMWTD-10)were pseudogenes by presenting one or more infram stop codons in the coding region. The highesthomology among the cloned genes and other typical genes in GenBank was99%, indicating that fourcloned genes are the new members of LMW-GS genes family. So all the4sequences were submitted to thepublic database with the GenBank accession number of KJ666139、KJ666137、KJ666138andKJ666140.(2) First amino acid of the deduced mature proteins of four LMW-GS genes was isoleucine amino acidresidues, so they were all classed to LMW-m type glutenins as well as to C type genes owing to theirmolecular weight respectively. Four LMW-GS gene sequences showed a clear structural organization of thepolypeptide comparing with other low molecular weight glutenin are all composed of signal peptide,N-terminal region, repetitive region, C-terminal region. LMWTD-3and LMWTD-4had eight cysteine, butLMWTD-1and LMWTD-2are lack of a cystine, contains seven cysteine. LMW-GS subunit containing8cysteine,which is the extension of protein subunit polymerization chain, is conducive to the increase ofpolymer molecules, which is beneficial to increase the LWM-GS interaction the polymerization ability and may cause high share of Glutenin LMW-GS, which effects of flour quality(3) In the present research, the new cloned genes were predicted with PISPRED3.0, the resultssuggested that positions and the core sequences of α-helix and β-sheet in LMW–GS were relativelyconservative. The signal peptide and C-terminal region consisted of manyα-helixs, the N-terminal regionwas formed by a short section of both α-helix and coils. A small amount of β-sheet structure wasobserved only in C-terminal region.. The repetitive region was many occupied by coil.Secondary structureprediction to reveal molecular functions has a certain reference value.(4) Evolutionary analysis among the cloned genes and other56LMW-GS genes on chromosomes.1Aand1B in triticum published in GenBank showed that LMW-GS sequencesn were distinguished accordingto the genome of origion on basis of sequence similarity which A genome subunit genes and B genomesubunit genes were clustered together respectively. LMWTD-1、LMWTD-3、LMWTD-4were morehomologous with the genes at the Glu-A3in triticum, and might be encoded by the locus of Glu-A3whileLMWTD-2was more homologous with the genes at the Glu-B3in triticum, and might be encoded by thelocus of Glu-B3.