Identification of LMW Glutenin-Like Genes from <Emphasis Type="Italic">Secale sylvestre</Emphasis> Host

Three low-molecular-weight (LMW) glutenin-like genes (designated as Ssy1, Ssy2, and Ssy3) from Secale sylvestre Host were isolated and characterized. The three genes consist of a predicted highly conservative signal peptide with 20 amino acids, a short N-terminal region with 13 amino acids, a highly variable repetitive domain and a less variable C-terminal domain. The deduced amino acid sequences of the three genes were the LMW-m type due to a methionine residue at the N-terminus. The phylogenetic analysis indicated that the prolamin genes could be perfectly clustered into five groups, including HMW-GS, LMW-GS, α/β-, γ-, and κ-prolamin. The LMW glutenin-like genes of S. sylvestre were more orthologous with the LMW-GS genes of wheat and B hordein genes of barley, which also had been confirmed by the homology analysis with the LMW-GS of wheat at Glu-A3, Glu-B3, and Glu-D3 loci. These results indicated that a chromosome locus (designated as Glu-R3) might be located on the R genome of S. sylvestre with the functions similar to the Glu-3 locus in wheat and its related species.     

<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.     

Transgenic citrus expressing synthesized <Emphasis Type="Italic">cecropin</Emphasis> B genes in the phloem exhibits decreased susceptibility to Huanglongbing

Key message

Expression of synthesized cecropin B genes in the citrus phloem, where Candidatus Liberibacter asiaticus resides, significantly decreased host susceptibility to Huanglongbing.

Abstract

Huanglongbing (HLB), associated with Candidatus Liberibacter asiaticus bacteria, is the most destructive disease of citrus worldwide. All of the commercial sweet orange cultivars lack resistance to this disease. The cationic lytic peptide cecropin B, isolated from the Chinese tasar moth (Antheraea pernyi), has been shown to effectively eliminate bacteria. In this study, we demonstrated that transgenic citrus (Citrus sinensis Osbeck) expressing the cecropin B gene specifically in the phloem had a decreased susceptibility to HLB. Three plant codon-optimized synthetic cecropin B genes, which were designed to secrete the cecropin B peptide into three specific sites, the extracellular space, the cytoplasm, and the endoplasmic reticulum, were constructed. Under the control of the selected phloem-specific promoter GRP1.8, these constructs were transferred into the citrus genome. All of the cecropin B genes were efficiently expressed in the phloem of transgenic plants. Over more than a year of evaluation, the transgenic lines exhibited reduced disease severity. Bacterial populations in transgenic lines were significantly lower than in the controls. Two lines, in which bacterial populations were significantly lower than in others, showed no visible symptoms. Thus, we demonstrated the potential application of the phloem-specific expression of an antimicrobial peptide gene to protect citrus plants from HLB.

     

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.     

Sequence diversification in recessive alleles of two host factor genes suggests adaptive selection for bymovirus resistance in cultivated barley from East Asia

Key message

Two distinct patterns of sequence diversity for the recessive alleles of two host factors HvPDIL5 - 1 and HvEIF4E indicated the adaptive selection for bymovirus resistance in cultivated barley from East Asia.

Abstract

Plant pathogens are constantly challenging plant fitness and driving resistance gene evolution in host species. Little is known about the evolution of sequence diversity in host recessive resistance genes that interact with plant viruses. Here, by combining previously published and newly generated targeted re-sequencing information, we systematically analyzed natural variation in a broad collection of wild (Hordeum spontaneum; Hs) and domesticated barleys (Hordeum vulgare; Hv) using the full-length coding sequence of the two host factor genes, HvPDIL5-1 and HvEIF4E, conferring recessive resistance to the agriculturally important Barley yellow mosaic virus (BaYMV) and Barley mild mosaic virus (BaMMV). Interestingly, two types of gene evolution conferred by sequence variation in domesticated barley, but not in wild barley were observed. Whereas resistance-conferring alleles of HvEIF4E exclusively contained non-synonymous amino acid substitutions (including in-frame sequence deletions and insertions), loss-of-function alleles were predominantly responsible for the HvPDIL5-1 conferred bymovirus resistance. A strong correlation between the geographic origin and the frequency of barley accessions carrying resistance-conferring alleles was evident for each of the two host factor genes, indicating adaptive selection for bymovirus resistance in cultivated barley from East Asia.

     

Molecular phylogeny of pectinase genes <Emphasis Type="Italic">PGU</Emphasis> in the yeast genus <Emphasis Type="Italic">Saccharomyces</Emphasis>

Using yeast genome databases and literature data, phylogenetic analysis of pectinase PGU genes from 112 Saccharomyces strains assigned to the biological species S. arboricola, S. bayanus (var. uvarum), S. cariocanus, S. cerevisiae, S. kudriavzevii, S. mikatae, S. paradoxus, and the hybrid taxon S. pastorianus (syn. S. carlsbergensis) was carried out. A superfamily of divergent PGU genes was found. Natural interspecies transfer of the PGU gene both from S. cerevisiae to S. bayanus and from S. paradoxus to S. cerevisiae may, however, occur. Within the Saccharomyces species, identity of the PGU nucleotide sequences was 98.8–100% for S. cerevisiae, 86.1–95.7% for S. bayanus (var. uvarum), 94–98.3% for S. kudriavzevii, and 96.8–100% for S. paradoxus/S. cariocanus. For the first time, a family of polymeric PGU1b, PGU2b, PGU3b and PGU4b genes is documented for the yeast S. bayanus var. uvarum, a variety important for winemaking.     

A <Emphasis Type="Italic">Vitis vinifera</Emphasis> xanthine dehydrogenase gene, <Emphasis Type="Italic">VvXDH</Emphasis>, enhances salinity tolerance in transgenic <Emphasis Type="Italic">Arabidopsis</Emphasis>

Xanthine dehydrogenase (EC1.1.1.204; XDH) plays an important role in purine catabolism that catalyzes the oxidative hydroxylation of hypoxanthine to xanthine and of xanthine to uric acid. Long attributed to its role in recycling and remobilization of nitrogen, recently, XDH is implicated in plant stress responses and acclimation, such research efforts, however, have thus far been restricted to Arabidopsis XDH-knockdown/knockout studies. This study, using an ectopic overexpression approach, is expected to provide novel findings. In this study, a XDH gene from Vitis vinifera, named VvXDH, was synthesized and overexpressed in Arabidopsis, the transgenic Arabidopsis showed enhanced salt tolerance. The VvXDH gene was investigated and the results demonstrated the explicit role of VvXDH in conferring salt stress by increasing allantoin accumulation and activating ABA signaling pathway, enhancing ROS scavenging in transgenic Arabidopsis. In addition, the water loss and chlorophyll content loss were reduced in transgenic plants; the transgenic plants showed higher proline level and lower MDA content than that of wild-type Arabidopsis, respectively. In conclusion, the VvXDH gene has the potential to be applied in increasing allantoin accumulation and enhancing the tolerance to abiotic stresses in Arabidopsis and other plants.     

Expressional characterization of galacturonosyltransferase-like gene family in <Emphasis Type="Italic">Eucalyptus grandis</Emphasis> implies a role in abiotic stress responses

Glycosyltransferase (GT) plays a pivotal role in cell wall biosynthesis in plants. Galacturonosyltransferase-like (GATL) genes, belonging to the GT8 family, have been proven to be involved in pectin and/or xylan biosynthesis of the cell wall. Here, we identified eight GATL genes from the Eucalyptus grandis genome and characterized the gene structure and chromosomal location. The genes were found to be distributed across five chromosomes, including two pairs in block duplication regions. None of the EgrGATL genes contained introns. And, with the exception of EgrGATL8, the remainder of the EgrGATL proteins possessed the three classic motifs characteristic of all GATL proteins. Expression analysis in the different tissues showed that EgrGATL1, EgrGATL4, and EgrGATL8 were highly expressed in xylem and phloem; EgrGATL6 exhibited the highest expression in leaves, and in phloem and leaves, EgrGATL2 and EgrGATL3 both exhibited very low expression. However, the abiotic stress response of plants can be affected by changes in the components and structure of the cell wall. The expression patterns of EgrGALTs under low-temperature, high-temperature, drought, salinity, and abscisic acid (ABA) treatments were assessed by qRT-PCR. The results showed that most of the EgrGATL genes could be induced under low temperature, and some were even able to increase their expression level under high temperature. Under drought conditions, the expression levels of most of the genes initially increased and then decreased. Similar expression patterns were observed in leaves under treatment with NaCl and ABA. Our results provide fundamental information towards the functional dissection of EgrGATL genes and their potential involvement in improving plant abiotic stress tolerance.     

Genetic Control of Meiosis in Plants

The genes controlling meiotic progression in plants and not affecting mitotic progression are most widely studied in maize Zea mays and cruciferous plant Arabidopsis thaliana. These include the genes controlling the differentiation of somatic cells into sporogenous ones and meiosis-initiating genes, genes encoding meiosis-specific proteins of chromosomes and synaptonemal complexes, genes of mediator proteins and enzymes of meiotic DNA recombination and crossover, and genes controlling meiosis-specific behavior of centromeres and the course of two meiotic divisions. A large number of such genes have been cloned and studied at the molecular level. The studies of meiotic genes in rice Oriza sativa are actively developing, while studies of corresponding genes in barley Hordeum vulgare, rye Secale cereale, tomato Solanum lycopersicum, and hexaploid wheat Triticum aestivum are less advanced. To identify meiotic genes, chemical and insertional mutagenesis, genetic and cytological analysis, genomic and proteomic studies, methods of reverse genetics, and bioinformatics are used.     

Genetic complementation analysis of rice sucrose transporter genes in Arabidopsis <Emphasis Type="Italic">SUC2</Emphasis> mutant <Emphasis Type="Italic">atsuc2</Emphasis>

Sucrose transporters (SUTs) play a critical role on the phloem plasma membrane in loading sucrose into the phloem of source leaves for long-distance transport to sink organs. Rice has a small gene family of five SUTs, Oryza sativa SUT1 (OsSUT1) to OsSUT5. To identify rice SUTs that function as phloem loaders, we adopted a growth restoration assay of the severe growth retardation phenotype of atsuc2, a mutant of the best-characterized Arabidopsis phloem loader AtSUC2, by introducing OsSUTs. The rice SUT genes were expressed by two different promoters, the native phloem-specific promoter of AtSUC2 (pAtSUC2) and the constitutive Cauliflower Mosaic Virus 35S (pCaMV35S) promoter. Of all the transgenic atsuc2 plants, only pAtSUC2: OsSUT1 complemented the atsuc2 mutant phenotype in a comparable manner to wild type (WT), and consistent levels of soluble sugars and starch were recovered compared to those of WT. This suggests that OsSUT1 is a functional ortholog of the Arabidopsis AtSUC2 and functions as an apoplastic phloem loader. In addition, ossut1 mutants were produced via anther culture and their primary carbohydrate levels and growth phenotypes were indistinguishable from those of WT. This suggests that the rice phloem loader OsSUT1 function may not be essential for rice vegetative growth under normal conditions.     

Contributions of <Emphasis Type="Italic">TaSUTs</Emphasis> to grain weight in wheat under drought

Key message

The homologous genes to OsSUT1-5 in wheat were identified and detailed analysed. TaSUT1 was the predominant sucrose transporter group and it illustrated the genotypic variations towards drought during grain filling.

Abstract

Sucrose transporters (SUT) play crucial roles in wheat stem water soluble carbohydrate (WSC) remobilization to grain. To determine the major functional SUT gene groups in shoot parts of wheat during grain development, drought tolerant varieties, Westonia and Kauz, were investigated in field drought experiments. Fourteen homologous genes to OsSUT1-5 were identified on five homeologous groups, namely TaSUT1_4A, TaSUT1_4B, TaSUT1_4D; TaSUT2_5A, TaSUT2_5B, TaSUT2_5D; TaSUT3_1A, TaSUT3_1D; TaSUT4_6A, TaSUT4_6B, TaSUT4_6D; TaSUT5_2A, TaSUT5_2B, and TaSUT5_2D, and their gene structures were analysed. Wheat plants above the ground were harvested from pre-anthesis to grain maturity and the stem, leaf sheath, rachis, lemma and developing grain were used for analysing TaSUT gene expression. Grain weight, thousand grain weight, kernel number per spike, biomass and stem WSC were characterized. The study showed that among the five TaSUT groups, TaSUT1 was the predominant sucrose transporting group in all organs sampled, and the expression was particularly high in the developing grain. In contrast to TaSUT1, the gene expression levels of TaSUT2, TaSUT3 and TaSUT4 were lower, except for TaSUT3 which showed preferential expression in the lemma before anthesis. The TaSUT5 gene group was very weakly expressed in all tissues. The upregulated gene expression of TaSUT1 Westonia type in stem and grain reveal a crucial role in stem WSC remobilization to grain under drought. The high TaSUT1 gene expression and the significant correlations with thousand grain weight (TGW) and kernel number per spike demonstrated the contribution in Kauz’s high grain yield in an irrigated environment and high TGW in Westonia under drought stress. Further molecular level identification is required for gene marker development.

     

Somatic hybrids between transgenic <Emphasis Type="Italic">Solanum tuberosum</Emphasis> potato plants and transplastome <Emphasis Type="Italic">Solanum rickii</Emphasis> plants

Experiments on fusion of mesophyllic protoplasts of Solanum tuberosum (Lugovskoi and Slavyanka cultivars) possessing the nptII gene in the nuclear DNA with transplastome Solanum rickii plants (which possess the aadA gene) that we have derived previously, are performed. Hybrid plants with the genes aadA and nptII, the chloroplasts of S. rickii and S. tuberosum, and a hybrid nuclear genome were obtained in a selection medium containing the antibiotics kanamycin, spectomycin, and streptomycin. The result is confirmed by results of PCR analyses.     

Fish growth hormone genes: Divergence of coding sequences in salmonid fishes

Comparison of coding nucleotide sequences of the paralogous GH1 and GH2 genes, as well as of the growth hormone amino acid sequences, in the species of closely related salmonid genera Salvelinus, Oncorhynchus, and Salmo was performed. It was demonstrated that, in different groups of salmonids, the amino acid substitution rates were considerably different. In some cases, an obvious discrepancy between the divergence of growth hormone genes and phylogenetic schemes based on other methods and approaches was revealed. These findings suggest that the reason may be multidirectional selection at duplicated genes at different stages of evolution.