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A novel HMW-GS of Dx5** with slightly faster migration rate than that of Dx5, was found in a Tibet bread wheat landrace using SDS-PAGE. Moreover, Dx5** is the subunit with the fastest migration rate in Glu-Dx locus. The gene for this subunit was isolated and its sequence was obtained in the present study. This gene was very similar to Dx5 both in nucleotide and deduced amino acid sequence. At the nucleotide sequence level, Dx5** different from Dx5 by the deletion of a 27 bp fragment and two nucleotide replacements at position 353(G/C) and 692(C/G), respectively. At the amino acid sequence level, Dx5** different from Dx5 by the deletion of a hexaploid (LGQGQQ) and a tripeptide (GQQ) repetitive motif and two amino acid replacements at position 118(C/S) and 231(A/G), respectively. These results suggested that the Dx5** was a derivation of Dx5 and was formed by replication slippage. Moreover, the specific cysteine (C) located at the beginning of the repetitive domain of Dx5, which proved to be critical for the end-use quality of wheat flours, was replaced by serine (S) in Dx5**.

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Two fundamental test systems were used to evaluate the visco-elastic properties of doughs from wheat samples of three varieties grown at four distinct sites. For comparison, tests were also performed with traditional equipment, namely the Mixograph, an extension tester and a Farinograph-type small-scale recording mixer. Uniaxial dough elongation (with an Instron) produced results similar to the conventional extension tester, except that results were provided in fundamental units (Pascals), the critical value recorded being the elongational stress at maximum strain. Stress relaxation measurements were performed following a small initial shear strain. With this method, it was possible to distinguish between the viscosity and the elastic components of dough visco-elasticity. In all the tests the extra dough-strength properties were evident for the variety (Guardian) that had the 5 + 10 glutenin subunits, in contrast to the other two with the 2 + 12 combination of subunits.

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Aegilops tauschii is the generally accepted D genome diploid donor of hexaploid wheat. The significance of Ae. tauschii HMW-GS genes on bread-making properties of bread wheat has been well documented. Among them, Ae. tauschii HMW-GS Dx5 t +Dy12 t was thought as the pair with potentially value in endowing synthetic hexaploid wheat with good end-use qualities. In this paper, we isolated and sequenced genes Dx5 t and Dy12 t from Ae. tauschii accession As63. Amino acid sequence comparison indicated that Dy12 t from Ae. tauschii is more similar to Dy10 rather than Dy12 of bread wheat. The sequence of Dx5 t in Ae. tauschii accession As63 showed higher similarity to that of Dx5 in bread wheat than others. However, it is notable that Dx5 t lacked the additional cysteine residue in Dx5, which is responsible for good bread-making quality in common wheat. Moreover, compared to Dx5, Dx5 t has an extra hexpeptide repetitive motif unit (SGQGQQ) as well as five amino acid substitutions.

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Cereal Research Communications
Authors: L. Zhang, Z. Yan, S. Dai, Q. Chen, Z. Yuan, Y. Zheng, and D. Liu

Two experiments to investigate the crossability of Triticum turgidum with Aegilops tauschii are described. In the first experiment, 372 wide hybridization combinations were done by crossing 196 T. turgidum lines belonging to seven subspecies with 13 Ae. tauschii accessions. Without embryo rescue and hormone treatment, from the 66220 florets pollinated, 3713 seeds were obtained, with a mean crossability percentages of 5.61% which ranged from 0 to 75%. A lot of hybrid seeds could germinate and produce plants. Out of 372 combinations, 73.12% showed a very low crossability less than 5%, 23.39% showed the crossability of 5–30%, 2.69% showed the crossability of 30–50%, 0.81% showed high crossability more than 50%, respectively. Among the seven T. turgidum subspecies, there were significant differences in crossability. The ssp. dicoccoides and dicoccon showed the highest crossability, while polonicum the lowest. All the crossability percentages more than 30% were obtained from the crossing of ssp. dicoccoides or dicoccon with Ae. tauschii .In the second experiment, the genetics of crossability was investigated using T. turgidum ssp. durum cultivar Langdon and the D-genome disomic substitution lines of Langdon. Compared with the control Langdon, lines 7D(7A) and 4D(4B) showed higher crossability, which suggested that chromosomes 7A and 4B of tetraploid wheat cv. Langdon carried dominant alleles inhibiting crossability with Ae. tauschii . The relationships of present results with previously reported crossability genes of wheat are discussed.

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Cereal Research Communications
Authors: S.F. Dai, D.Y. Xu, Z.J. Wen, Z.P. Song, H.X. Chen, H.Y Li, J.R. Li, L.Z. Kang, and Z.H. Yan

A novel 4.0-kb Fy was sequenced and bacterially expressed. This gene, the largest y-type HMW-GS currently reported, is 4,032-bp long and encodes a mature protein with 1,321 amino acid (AA) residues. The 4.0-kb Fy shows novel modifications in all domains. In the N-terminal, it contains only 67 AA residues, as three short peptides are absent. In the repetitive domain, the undecapeptide RYYPSVTSPQQ is completely lost and the dodecapeptide GSYYPGQTSPQQ is partially absent. A novel motif unit, PGQQ, is present in addition to the two standard motif units PGQGQQ and GYYPTSPQQ. Besides, an extra cysteine residue also occurs in the middle of this domain. The large molecular mass of the 4.0-kb Fy is mainly due to the presence of an extra-long repetitive domain with 1,279 AA residues. The novel 4.0-kb Fy gene is of interest in HMW-GS gene evolution as well as to wheat quality improvement with regard to its longest repetitive domain length and extra cysteines residues.

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New high-molecular-weight glutenin (HMW glutenin) sequences isolated from six Psathyrostachys juncea accessions by thermal asymmetric interlaced PCR differ from previous sequences from this species. They showed novel modifications in all of the structural domains, with unique C-terminal residues, and their N-terminal lengths were the longest among the HMW glutenins reported to date. In their repetitive domains, there were three repeatable motif units: 13-residue [GYWH(/I/Y)YT(/Q)S(/T)VTSPQQ], hexapeptide (PGQGQQ), and tetrapeptide (ITVS). The 13-residue repeats were restricted to the current sequences, while the tetrapeptides were only shared by D-hordein and the current sequences. However, these sequences were not expressed as normal HMW glutenin proteins because an in-frame stop codon located in the C-termini interrupted the intact open reading frames. A phylogenetic analysis supported different origins of the P. juncea HMW glutenin sequences than that revealed by a previous study. The current sequences showed a close relationship with D-hordein but appeared to be more primitive.

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Influence of different maturity stages and treatments of ethephon, exogenous ABA, and fluridone on the ripening and hormone level of ‘Zhonghuashoutao’ peach during development and post-harvest storage were investigated. The accumulation of endogenous ABA appeared at the onset of ripening and peaked at two weeks before harvest. Fruit firmness decreased, while ethylene release and SSC/TA increased sharply after a maximum peak of ABA, which have triggered the initiation of the fruit ripening. The fruits, harvested at 170 d when fruits have ripened and stored at 20 °C, showed an ethylene climacteric peak, and the pulp started softening normally, and the SSC/TA value increased. Compared with them, the immature green fruits harvested at other dates, could not mature normally due to the lack of normal reciprocity between ABA and ethylene. The ethylene release was promoted by the treatment of exogenous ABA and ethephon during ripening until the endogenous ABA reached a maximum value. However, fluridone treatment showed an inhibitory effect. The above-mentioned changes occurred again in the peach fruits after harvest. The results indicated that both ABA and ethylene play important roles in peach ripening, and their action depended on the ripening stage of peach.

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