Quantitative trait loci mapping of dark-induced senescence in winter wheat (Triticum aestivum).

In order to explore the genetics of dark-induced senescence in winter wheat (Triticum aestivum L.), a quantitative trait loci (QTL) analysis was carried out in a doubled haploid population developed from a cross between the varieties Hanxuan 10 (HX) and Lumai 14 (LM). The senescence parameters chlorophyll content (Chl a+b, Chl a, and Chl b), original fluorescence (Fo), maximum fluorescence level (Fm), maximum photochemical efficiency (Fv/Fm), and ratio of variable fluorescence to original fluorescence (Fv/Fo) were evaluated in the second leaf of whole three-leaf seedlings subjected to 7 d of darkness. A total of 43 QTLs were identified that were associated with dark-induced senescence using composite interval mapping. These QTLs were mapped to 20 loci distributed on 11 chromosomes: 1B, 1D, 2A, 2B, 3B, 3D, 5D, 6A, 6B, 7A, and 7B. The phenotypic variation explained by each QTL ranged from 7.5% to 19.4%. Eleven loci coincided with two or more of the analyzed parameters. In addition, 14 loci co-located or were linked with previously reported QTLs regulating flag leaf senescence, tolerance to high light stress, and grain protein content (Gpc), separately.

Molecular cloning and characterization of a novel glyoxalase I gene TaGly I in wheat (Triticum aestivum L.).

Methylglyoxal is a kind of poisonous metabolite that can react with RNA, DNA and protein, which generally results in a number of side advert effects to cell. Glyoxalase I is a member of glyoxalase system that can detoxify methylglyoxal. An EST encoding a glyoxalase I was isolated from a SSH (suppression subtractive hybridization)-cDNA library of wheat spike inoculated by Fusarium graminearum. The corresponding full length gene, named TaGly I, was cloned, sequenced and characterized. Its genomic sequence consists of 2,719 bp, including seven exons and six introns, and its coding sequence is 929 bp with an open reading frame encoding 291 amino acids. Sequence alignment showed that there were two glyoxalase I domains in the deduced protein sequence. By using specific primers, TaGly I was mapped to chromosome 7D of wheat via a set of durum wheat 'Langdon' D-genome disomic-substitution lines. The result of Real-time quantitative polymerase chain reaction demonstrated that TaGly I was induced by the inoculation of Fusarium graminearum in wheat spikes. Additionally, it was also induced by high concentration of NaCl and ZnCl2. When TaGly I was overexpressed in tobacco leaves via Agrobacterium tumefaciens infection, the transgenic tobacco showed stronger tolerance to ZnCl2 stress relative to transgenic control with GFP. The above facts indicated that TaGly I might play a role in response to diverse stresses in plants.

An ankyrin-repeat and WRKY-domain-containing immune receptor confers stripe rust resistance in wheat.

Perception of pathogenic effectors in plants often relies on nucleotide-binding domain (NBS) and leucine-rich-repeat-containing (NLR) proteins. Some NLRs contain additional domains that function as integrated decoys for pathogen effector targets and activation of immune signalling. Wheat stripe rust is one of the most devastating diseases of crop plants. Here, we report the cloning of YrU1, a stripe rust resistance gene from the diploid wheat Triticum urartu, the progenitor of the A genome of hexaploid wheat. YrU1 encodes a coiled-coil-NBS-leucine-rich repeat protein with N-terminal ankyrin-repeat and C-terminal WRKY domains, representing a unique NLR structure in plants. Database searches identify similar architecture only in wheat relatives. Transient expression of YrU1 in Nicotiana benthamiana does not induce cell death in the absence of pathogens. The ankyrin-repeat and coiled-coil domains of YrU1 self-associate, suggesting that homodimerisation is critical for YrU1 function. The identification and cloning of this disease resistance gene sheds light on NLR protein function and may facilitate breeding to control the devastating wheat stripe rust disease.

[Cloning and expression analysis of drought-tolerant and wa-ter-saving related gene PmMYB in broomcorn millet].

Exploring novel genes and gene combinations are of primary importance in plant drought-tolerance and water-saving research. Based on the EST sequence of MYB gene obtained in the research on molecular basis of drought-tolerance and water-saving in broomcorn millet (Panicum miliaceum L.), a 1 739 bp genomic sequence of MYB gene, designated PmMYB, was amplified using primers based on this EST sequence and that of rice MYB18. Sequence analysis indicated that PmMYB consisted of 2 introns, 121 bp (347-467 bp) and 93 bp (599-691 bp) in length respectively, and 3 extrons. The full-length cDNA sequence of PmMYB is 1 525 bp, which includes 212 bp 3' untranslated region, 41 bp 5' untranslated region, and 1 272 bp coding region which encodes 424 amino acids with a serine-rich region. PmMYB is a typical R2, R3-MYB transcription factor with its 2 typical DNA-binding domains (amino acid sites of 13-63 and 66-114). The multiple alignment of R2, R3 amino acid repeat regions of MYB genes among broomcorn millet, rice, corn, loblolly pine, Arabidopsis, capsicum, upland cotton, barley and aubergine indicates that R2, R3 repeat regions are very conserved. The phylogenetic analysis based on amino acid sequence shows that MYB genes are highly divergent with similarity ranging from 32% to 84%. PmMYB has the highest similarity (84%) with MYB18 gene of rice, whereas 46% and 41% with barley and corn, respectively. Semi-quantitative RT-PCR confirmed that PmMYB was upregulated by water stress and re-watering in broomcorn millet. Cloning this gene may provide a good foundation to improve the drought-tolerance and water-saving in broomcorn millet as well as in other plants.

[Cloning and expression analysis of two salt and Fusarium graminearum stress associated UDP-glucosyltransferases genes in wheat].

Glycosyltransferases (GTs) play important roles in stress responses of plants by glycosylating hormones and secondary metabolites. UDP-glucosyltransferases (UGTs), which use UDP-glucuronic acid in animals, UDP-glucose, UDP-galactose, and UDP- rhamnose in plant as sugar donors, belong to family 1 of GTs. As a secondary metabolite produced by Fusarium graminearum during infection of grains, deoxynivalenol (DON) is not only harmful to human and animal's health by inhibiting protein synthesis, but also acts as a virulence factor during fungal pathogenesis. In order to study expression profile of UGT genes in wheat, two UGTs, designated TaUGT1 and TaUGT2, were isolated from bread wheat (Triticum aestivum L.) by reverse transcriptase-polymerase chain reaction. The genomic sequences of both genes had one intron. Their coding sequences shared 91% and 90% similarities at nucleic acid level and the deduced protein sequence level. The analysis of conserved domain revealed that these two cDNAs encoded UDP-glucoronosyl and UDP-glucosyl transferase with PSPG (Putative secondary plant glycosyltransferase) domain. Real-time PCR was carried out to detect the expression profiles of the two UGTs in wheat under various stress conditions. In young spikes infected by Fusarium graminearum, TaUGT2 was induced but TaUGT1 was repressed. These two genes were upregulated under higher NaCl concentration. In conclusion, TaUGT2 may participate in wheat resistance to Fusarium head blight in which mycotoxin DON plays a role, and these two genes might be involved in responses of wheat to salt stress.

Genetic structure and diversity of cultivated soybean (Glycine max (L.) Merr.) landraces in China.

The Chinese genebank contains 23,587 soybean landraces collected from 29 provinces. In this study, a representative collection of 1,863 landraces were assessed for genetic diversity and genetic differentiation in order to provide useful information for effective management and utilization. A total of 1,160 SSR alleles at 59 SSR loci were detected including 97 unique and 485 low-frequency alleles, which indicated great richness and uniqueness of genetic variation in this core collection. Seven clusters were inferred by STRUCTURE analysis, which is in good agreement with a neighbor-joining tree. The cluster subdivision was also supported by highly significant pairwise Fst values and was generally in accordance with differences in planting area and sowing season. The cluster HSuM, which contains accessions collected from the region between 32.0 and 40.5 degrees N, 105.4 and 122.2 degrees E along the central and downstream parts of the Yellow River, was the most genetically diverse of the seven clusters. This provides the first molecular evidence for the hypotheses that the origin of cultivated soybean is the Yellow River region. A high proportion (95.1%) of pairs of alleles from different loci was in LD in the complete dataset. This was mostly due to overall population structure, since the number of locus pairs in LD was reduced sharply within each of the clusters compared to the complete dataset. This shows that population structure needs to be accounted for in association studies conducted within this collection. The low value of LD within the clusters can be seen as evidence that much of the recombination events in the past have been maintained in soybean, fixed in homozygous self-fertilizing landraces.

Electrochemistry and electrocatalysis of polyoxometalate-ordered mesoporous carbon modified electrode.

In this work, we have developed a convenient and efficient method for the functionalization of ordered mesoporous carbon (OMC) using polyoxometalate H6P2Mo18O62 x H2O (P2Mo18). By the method, glassy carbon (GC) electrode modified with P(2)Mo(18) which was immobilized on the channel surface of OMC was prepared and characterized for the first time. The large specific surface area and porous structure of the modified OMC particles result in high heteropolyacid loading, and the P(2)Mo(18) entrapped in this order matrix is stable. Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption-desorption isotherm and X-ray diffraction (XRD) were employed to give insight into the intermolecular interaction between OMC and P(2)Mo(18). The electrochemical behavior of the modified electrode was studied in detail, including pH-dependence, stability and so on. The cyclic voltammetry (CV) and amperometry studies demonstrated that P(2)Mo(18)/OMC/GC electrode has high stability, fast response and good electrocatalytic activity for the reduction of nitrite, bromate, idonate, and hydrogen peroxide. The mechanism of catalysis on P(2)Mo(18)/OMC/GC electrode was discussed. Moreover, the development of our approach for OMC functionalization suggests the potential applications in catalysis, molecular electronics and sensors.