Structure and expression of the <Emphasis Type="Italic">TaGW7</Emphasis> in bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

OsGW7 (also known as OsGL7) is homologous to the Arabidopsis thaliana gene that encodes LONGIFOLIA protein, which regulates cell elongation, and is involved in regulating grain length in rice. However, our knowledge on its ortholog in wheat, TaGW7, is limited. In this study, we identified and mapped TaGW7 in wheat, characterized its nucleotide and protein structures, predicted the cis-elements of its promoter, and analysed its expression patterns. The GW7 orthologs in barley (HvGW7), rice (OsGW7), and Brachypodium distachyon (BdGW7) were also identified for comparative analyses. TaGW7 mapped onto the short arms of group 2 chromosomes (2AS, 2BS, and 2DS). Multiple alignments indicated GW7 possesses five exons and four introns in all but two of the species analysed. An exon–intron junction composed of introns 3–4 and exons 4–5 was highly conserved. GW7 has a conserved domain (DUF 4378) and two neighbouring low complexity regions. GW7 was mainly expressed in wheat spikes and stems, in barley seedling crowns, and in rice anthers and embryo-sacs during early development. Drought and heat significantly increased and decreased GW7 expression in wheat, respectively. In barley, GW7 was significantly down-regulated in paleae and awns but up-regulated in seeds under drought treatment and down-regulated under Fusarium and stem rust inoculation. In rice, OsGW7 expression differed significantly under drought treatments. Collectively, these results provide insights into GW7 structure and expression in wheat, barley and rice. The GW7 sequence structure and expression data are the foundation for manipulating GW7 and uncovering its roles in plants.     

An UDP-Glucosyltransferase Gene from Barley Confers Disease Resistance to <Emphasis Type="Italic">Fusarium</Emphasis> Head Blight

UDP-glucosyltransferases (UGTs) contribute to Fusarium head blight (FHB) resistance of wheat and barley by glycosylating the deoxynivalenol (DON), which is produced by Fusarium fungus. In this study, seven alleles of barley HvUGT14077 (GenBank No.GU170356.1) were cloned using RT-PCR. Among them, HvUGT-10W1, which was isolated from a FHB resistant barley variety 10W1, was significantly up-regulated in young spikes after F. graminearum (F.g) inoculation. HvUGT-10W1::GFP was subcellularly located in the plasma membrane and cytoplasm of the wheat protoplasts. In vitro antifungal activity assay showed that the HvUGT-10W1 protein exerted obvious inhibition against the growth of F.g. The silencing of the HvUGT-10W1 by virus-induced gene silencing (VIGS) resulted in compromised FHB resistance of 10W1, which was shown by the increased infected colonies on the leaves. These indicated that the barley HvUGT-10W1 may also contribute to F.g resistance in barley and provided a potential candidate gene to develop transgenic barley with enhanced FHB resistance.     

Biocontrol of the toxigenic plant pathogen <Emphasis Type="Italic">Fusarium culmorum</Emphasis> by soil fauna in an agroecosystem

In 2011 and 2013, a field experiment was conducted in a winter wheat field at Adenstedt (northern Germany) to investigate biocontrol and interaction effects of important members of the soil food web (Lumbricus terrestris, Annelida; Folsomia candida, Collembola and Aphelenchoides saprophilus, Nematoda) on the phytopathogenic fungus Fusarium culmorum in wheat straw. Therefore, soil fauna was introduced in mesocosms in defined numbers and combinations and exposed to either Fusarium-infected or non-infected wheat straw. L. terrestris was introduced in all faunal treatments and combined either with F. candida or A. saprophilus or both. Mesocosms filled with a Luvisol soil, a cover of different types of wheat straw and respective combinations of faunal species were established outdoors in the topsoil of a winter wheat field after harvest of the crop. After a time span of 4 and 8 weeks, the degree of wheat straw coverage of mesocosms was quantified to assess its attractiveness for the soil fauna. The content of Fusarium biomass in residual wheat straw and soil was determined using a double-antibody sandwich (DAS)-ELISA method. In both experimental years, the infected wheat straw was incorporated more efficiently into the soil than the non-infected control straw due to the presence of L. terrestris in all faunal treatments than the non-infected control straw. In addition, Fusarium biomass was reduced significantly in all treatments after 4 weeks (2011: 95–99%; 2013:15–54%), whereupon the decline of fungal biomass was higher in faunal treatments than in non-faunal treatments and differed significantly from them. In 2011, Fusarium biomass of the faunal treatments was below the quantification limit after 8 weeks. In 2013, a decline of Fusarium biomass was observed, but the highest content of Fusarium biomass was still found in the non-faunal treatments after 8 weeks. In the soil of all treatments, Fusarium biomass was below the quantification limit. The earthworm species L. terrestris revealed a considerable potential as an effective biocontrol agent contributing to a sustainable control of a Fusarium plant pathogen in wheat straw, thus reducing the infection risk for specific plant diseases in arable fields.     

<Emphasis Type="Italic">Sr33</Emphasis> and <Emphasis Type="Italic">Sr35</Emphasis> gene homolog identification in genomes of cereals related to <Emphasis Type="Italic">Aegilops tauschii</Emphasis> and <Emphasis Type="Italic">Triticum monococcum</Emphasis>

Using bioinformatics analysis, the homologs of genes Sr33 and Sr35 were identified in the genomes of Triticum aestivum, Hordeum vulgare, and Triticum urartu. It is known that these genes confer resistance to highly virulent wheat stem rust races (Ug99). To identify amino acid sites important for this resistance, the found homologs were compared with the Sr33 and Sr35 protein sequences. It was found that sequences S5DMA6 and E9P785 are the closest homologs of protein RGAle, a Sr33 gene product, and sequences M7YFA9 (CNL-C) and F2E9R2 are homologs of protein CNL9, a Sr35 gene product. It is assumed that the homologs of genes Sr33 and Sr35, which were obtained from the wild relatives of wheat and barley, can confer resistance to various forms of stem rust and can be used in the future breeding programs aimed at improvement of national wheat varieties.     

Taxonomic study on <Emphasis Type="Italic">Alternaria</Emphasis> sections <Emphasis Type="Italic">Infectoriae</Emphasis> and <Emphasis Type="Italic">Pseudoalternaria</Emphasis> associated with black (sooty) head mold of wheat and barley in Iran

During the spring and summer of 2014 and 2015, wheat and barley fields in the Iranian provinces of Golestan and Alborz showed a high incidence of symptoms of black (sooty) head mold of wheat and barley. The isolation results revealed that Alternaria was associated with these symptoms. One hundred and forty isolates were collected and morphologically characterized based on the development of conidial chains with primary, secondary, and tertiary branching patterns, consistent with the three-dimensional sporulation complexity of members of Alternaria in sections Infectoriae and Pseudoalternaria. Subsequently, 16 Alternaria isolates exhibiting high morphological diversity were characterized based on extensive morphological and molecular comparisons. Phylogenetic analyses of three loci [ITS, glyceraldehyde 3-phosphate dehydrogenase (gpd), and plasma membrane ATPase (ATPase)] revealed that 15 isolates belonged to section Infectoriae but could not be assigned to phylogenetic species and one isolate represents a new species, Alternaria kordkuyana sp. nov., in section Pseudoalternaria. Morphological assessments revealed a high degree of variation among section Infectoriae isolates and that A. kordkuyana has significant morphological differences as compared to the three other species currently described in section Pseudoalternaria.     

Structure of the <Emphasis Type="Italic">TADHN</Emphasis> gene for dehydrin-like protein of soft wheat and activation of its expression by ABA and 24-epibrassinolide

The structure of the cloned fragment of wheat (Triticum aestivum L.) TADHN gene encoding dehydrin-like protein was examined. A comparative analysis of nucleotide and deduced amino acid sequences revealed a high homology of this fragment with sequences of the barley dhn8 gene and wheat wcor gene family. In deduced amino acid sequence of the TADHN fragment, a 15-residue region EKKGFLEKIKEKLPG was found, which corresponded to a highly conserved K-segment of dehydrins. Wheat seedling treatment with 3.7 μM ABA and 0.4 μM 24-epibrassinolide exerted similar stimulatory effects on expression of the TADHN gene, which indicates the involvement of dehydrins in the protective action of these phytohormones in wheat plants.     

Genome-wide identification and resistance expression analysis of the <Emphasis Type="Italic">NBS</Emphasis> gene family in <Emphasis Type="Italic">Triticum urartu</Emphasis>

As the largest class of resistant genes, the nucleotide binding site (NBS) has been studied extensively at a genome-wide level in rice, sorghum, maize, barley and hexaploid wheat. However, no such comprehensive analysis has been conducted of the NBS gene family in Triticum urartu, the donor of the A genome to the common wheat. Using a bioinformatics method, 463 NBS genes were isolated from the whole genome of T. urartu, of which 461 had location information. The expansion pattern and evolution of the 461 NBS candidate proteins were analyzed, and 118 of them were duplicated. By calculating the lengths of the copies, it was inferred that the NBS resistance gene family of T. urartu has experienced at least two duplication events. Expression analysis based on RNA-seq data found that 6 genes were differentially expressed among Tu38, Tu138 and Tu158 in response to Blumeria graminis f.sp.tritici (Bgt). Following Bgt infection, the expression levels of these genes were up-regulated. These results provide critical references for further identification and analysis of NBS family genes with important functions.     

Evolution of <Emphasis Type="Italic">VRN-1</Emphasis> homoeologous loci in allopolyploids of <Emphasis Type="Italic">Triticum</Emphasis> and their diploid precursors

Background

The key gene in genetic system controlling the duration of the vegetative period in cereals is the VRN1 gene, whose product under the influence of low temperature (vernalization) promotes the transition of the apical meristem cells into a competent state for the development of generative tissues of spike. As early genetic studies shown, the dominant alleles of this gene underlie the spring forms of plants that do not require vernalization for this transition. In wheat allopolyploids various combinations of alleles of the VRN1 homoeologous loci (VRN1 homoeoalleles) provide diversity in such important traits as the time to heading, height of plants and yield. Due to genetical mapping of VRN1 loci it became possible to isolate the dominant VRN1 alleles and to study their molecular structure compared with the recessive alleles defining the winter type of plants. Of special interest is the process of divergence of VRN1 loci in the course of evolution from diploid ancestors to wheat allopolyploids of different levels of ploidy.

Results

Molecular analysis of VRN1 loci allowed to establish that various dominant alleles of these loci appeared as a result of mutations in two main regulatory regions: the promoter and the first intron. In the diploid ancestors of wheat, especially, in those of A- genome (T. boeoticum, T. urartu), the dominant VRN1 alleles are rare in accordance with a limited distribution of spring forms in these species. In the first allotetraploid wheat species including T. dicoccoides, T. araraticum (T. timopheevii), the spring forms were associated with a new dominant alleles, mainly, within the VRN-A1 locus. The process of accumulation of new dominant alleles at all VRN1 loci was significantly accelerated in cultivated wheat species, especially in common, hexaploid wheat T. aestivum, as a result of artificial selection of spring forms adapted to different climatic conditions and containing various combinations of VRN1 homoeoalleles.

Conclusions

This mini-review summarizes data on the molecular structure and distribution of various VRN1 homoeoalleles in wheat allopolyploids and their diploid predecessors.

     

Effects of transgenic expression of <Emphasis Type="Italic">Brevibacterium linens</Emphasis> methionine gamma lyase (MGL) on accumulation of <Emphasis Type="Italic">Tylenchulus semipenetrans and key aminoacid contents</Emphasis> in <Emphasis Type="Italic">Carrizo citrange</Emphasis>

Alpha-dioxygenases (α-DOX) catalyzing the primary oxygenation of fatty acids to oxylipins were recently found in plants. Here, the biological roles of the pepper α-DOX (Ca-DOX) gene, which is strongly induced during non-host pathogen infection in chili pepper, were examined. Virus-induced gene silencing demonstrated that down-regulation of Ca-DOX enhanced susceptibility to bacterial pathogens and suppressed the hypersensitive response via the suppression of pathogenesis-related genes such as PR4, proteinase inhibitor II and lipid transfer protein (PR14). Ca-DOX-silenced pepper plants also exhibited more retarded growth with lower epidermal cell numbers and reduced cell wall thickness than control plants. To better understand regulation of Ca-DOX, transgenic Arabidopsis plants harboring the β-glucuronidase (GUS) reporter gene driven from a putative Ca-DOX promoter were generated. GUS expression was significantly induced upon avirulent pathogen infection in transgenic Arabidopsis leaves, whereas GUS induction was relatively weak upon virulent pathogen treatment. After treatment with plant hormones, early and strong GUS expression was seen after treatment of salicylic acid, whereas ethylene and methyl jasmonate treatments produced relatively weak and late GUS signals. These results will enable us to further understand the role of α-DOX, which is important in lipid metabolism, defense responses, and growth development in plants.     

Expression Profiles of Pathogenesis-Related Gene, <Emphasis Type="Italic">TaLr35PR1</Emphasis>, as it Relate to <Emphasis Type="Italic">Lr35</Emphasis>-Mediated Adult Plant Leaf Rust Resistance

Plants have developed sophisticated mechanisms to combat pathogen infection. One of the acquired modes in response to pathogen attack is the production of the pathogenesis-related (PR) proteins. Our earlier studies reported that TaLr35PR1, a PR1 gene encoding a protein with conserved serine carboxypeptidase (SCP) domain, has been cloned from wheat near-isogenic line TcLr35. However, the involvement of TaLr35PR1 in wheat growth and Lr35-mediated adult resistance to Puccinia triticina remains unclear. Here, we showed that TaLr35PR1 was strongly induced by P. triticina in wheat plant containing Lr35 (TcLr35), in which the expression level of TaLr35PR1 significantly increased and reached the maximum at 12 hpi. The accumulations of TaLr35PR1 increased stably and showed significant peak challenged by P. triticina at different growth and development periods of TcLr35 wheat while it maintained similar level and changed little in mock inoculated. Western blotting was conducted to confirm that TaLr35PR1 protein was increasingly accumulated in the TcLr35 adult plants after P. triticina inoculation and maintained at a similar level from 120 to 168 h post-inoculation. Similar to the expression patterns of TaLr35PR1 at RNA levels, the accumulations of TaLr35PR1 protein were weak in the seedling stage and then increased to the peak and kept constant levels at the mature stage which is consistent with the expression feature of Lr35 gene as an adult plant resistance gene. All these findings suggest that TaLr35PR1 is involved in wheat growth and Lr35-mediated adult wheat defense response to leaf rust pathogen attack.