Uracil-DNA N-glycosylase (UNG) from the marine, psychrophilic bacterium Vibrio salmonicida shows cold adapted features: A comparative analysis to Vibrio cholerae uracil-DNA N-glycosylase

The genes encoding uracil-DNA N-glycosylase (UNG) from the marine, psychrophilic bacterium Vibrio salmonicida and the mesophilic counterpart Vibrio cholerae have been cloned and expressed in Escherichia coli. The purified proteins have been characterized in order to reveal possible cold adapted features of the V. salmonicida UNG (vsUNG) compared to the V. cholerae UNG (vcUNG). Characterization experiments demonstrated that both enzymes possessed the highest activities at pH 7.0–7.5 and at salt concentrations in the range of 25–50 mM NaCl. Temperature optima for activity were determined to approximately 30 °C for vsUNG and 50 °C for vcUNG. Temperature stability of the enzymes was compared at 4 °C and 37 °C, and vsUNG was found to be more temperature labile than vcUNG. Kinetic studies performed at three different temperatures, 15 °C, 22 °C and 37 °C, demonstrated higher catalytic efficiency for vsUNG compared to vcUNG due to lower K_M-values. The increased substrate affinity of vsUNG is probably caused by an increased number of positively charged residues in the DNA-binding site of the enzyme compared to vcUNG. Thus, activity and stability measurements reveal typical cold adapted features of vsUNG.     

Differential Water Mite Parasitism,Phenoloxidase Activity,and Resistance to Mites Are Unrelated across Pairs of Related Damselfly Species

Related host species often demonstrate differences in prevalence and/or intensity of infection by particular parasite species, as well as different levels of resistance to those parasites. The mechanisms underlying this interspecific variation in parasitism and resistance expression are not well understood. Surprisingly, few researchers have assessed relations between actual levels of parasitism and resistance to parasites seen in nature across multiple host species. The main goal of this study was to determine whether interspecific variation in resistance against ectoparasitic larval water mites either was predictive of interspecific variation in parasitism for ten closely related species of damselflies (grouped into five “species pairs”), or was predicted by interspecific variation in a commonly used measure of innate immunity (total Phenoloxidase or potential PO activity). Two of five species pairs had interspecific differences in proportions of individuals resisting larval Arrenurus water mites, only one of five species pairs had species differences in prevalence of larval Arrenurus water mites, and another two of five species pairs showed species differences in mean PO activity. Within the two species pairs where species differed in proportion of individuals resisting mites the species with the higher proportion did not have correspondingly higher PO activity levels. Furthermore, the proportion of individuals resisting mites mirrored prevalence of parasitism in only one species pair. There was no interspecific variation in median intensity of mite infestation within any species pair. We conclude that a species’ relative ability to resist particular parasites does not explain interspecific variation in parasitism within species pairs and that neither resistance nor parasitism is reflected by interspecific variation in total PO or potential PO activity.     

Herbivore host plant selection: whitefly learns to avoid host plants that harbour predators of her offspring

Evidence is accumulating that herbivorous arthropods do not simply select host plants based on their quality, but also on the predation risk associated with different host plants. It has been suggested that herbivores exclude plant species with high predation risk from their host range. This assumes a constant, predictable predation risk as well as a rather static behaviour on the part of the herbivore; plants are ignored irrespective of the actual predation risk. We show that adult females of a small herbivore, the whitefly Bemisia tabaci, can learn to avoid plants with predatory mites that attack only juvenile whiteflies, while they accept host plants of the same species without predators. Predatory mites disperse more slowly than whiteflies; they cannot fly and walk from plant to plant. Hence, by avoiding plants with predators, the whiteflies create a temporary refuge for their offspring. We suggest that the experience of arthropod herbivores with risks associated with host plants plays an important role in their host plant selection.     

The New Caledonian genus Caledonotrichia Sykora (Trichoptera,Insecta) reviewed,with?descriptions?of?6?new species

The New Caledonian endemic hydroptilid genus Caledonotrichia Sykora (Trichoptera) is reviewed and 6 new species are described: Caledonotrichia bifida, Caledonotrichia capensis, Caledonotrichia minuta, Caledonotrichia ouinnica, Caledonotrichia sykorai and Caledonotrichia vexilla. Together with the established species for which revised diagnoses are given, these raise to 11 the number of species known in this genus. The new species, females of 3 species, and several unusual larval cases are examined and described for further insight into relationships of this enigmatic genus. A key to species is provided.     

Insights into species diversity of the genus Hydropsyche Pictet, 1834 (Hydropsychidae,Trichoptera) from the Lake Kinneret catchment (Israel)

Species identification based on larval stages of aquatic insects in Israel is difficult, given the paucity of taxonomic studies. In order to gain deeper understanding of biological processes in Israel's freshwater ecosystems and to develop a bioindication system, species have to be known and characterised at all life stages. Here, we applied an integrative morphological and genetic approach to characterise caddisflies of the genus Hydropsyche Pictet, 1834 from the Lake Kinneret catchment. Seventeen sites in the Lake Kinneret catchment were sampled in spring/summer 2015 and 2016. For 77 hydropsychid larvae and two adult specimens of H. yahfufah Malicky, 2001, we analysed a 658 bp fragment of the mitochondrial COI gene and compared the results of different genetic species delimitation methods to observed morphological variation. Our results suggest the presence of at least five species. This study is an important first step towards assessing stream biodiversity of a yet largely understudied region and highlights advantages of integrative taxonomic approaches.     

Loss of T-cell protein tyrosine phosphatase induces recycling of the platelet-derived growth factor (PDGF) beta-receptor but not the PDGF alpha-receptor

We have previously shown that the T-cell protein tyrosine phosphatase (TC-PTP) dephosphorylates the platelet-derived growth factor (PDGF) beta-receptor. Here, we show that the increased PDGF beta-receptor phosphorylation in TC-PTP knockout (ko) mouse embryonic fibroblasts (MEFs) occurs primarily on the cell surface. The increased phosphorylation is accompanied by a TC-PTP-dependent, monensin-sensitive delay in clearance of cell surface PDGF beta-receptors and delayed receptor degradation, suggesting PDGF beta-receptor recycling. Recycled receptors could also be directly detected on the cell surface of TC-PTP ko MEFs. The effect of TC-PTP depletion was specific for the PDGF beta-receptor, because PDGF alpha-receptor homodimers were cleared from the cell surface at the same rate in TC-PTP ko MEFs as in wild-type MEFs. Interestingly, PDGF alphabeta-receptor heterodimers were recycling. Analysis by confocal microscopy revealed that, in TC-PTP ko MEFs, activated PDGF beta-receptors colocalized with Rab4a, a marker for rapid recycling. In accordance with this, transient expression of a dominant-negative Rab4a construct increased the rate of clearance of cell surface receptors on TC-PTP ko MEFs. Thus, loss of TC-PTP specifically redirects the PDGF beta-receptor toward rapid recycling, which is the first evidence of differential trafficking of PDGF receptor family members.     

Mapping and validation of powdery mildew resistance loci from spring wheat cv. Naxos with SNP markers

Powdery mildew, caused by Blumeria graminis f.sp. tritici, is a major wheat disease in maritime and temperate climates. Breeding for race-non-specific or partial resistance is a cost-effective and environmentally friendly disease control strategy. The German spring wheat cultivar Naxos has proven to be a good source for partial resistance to powdery mildew. The objectives of the present study were to map the resistance loci in Naxos with use of high-density SNP markers in the Shanghai3/Catbird x Naxos inbred line population and validate the results in a different genetic background; Soru#1 x Naxos. Both populations were genotyped with the Illumina iSelect 90K wheat chip, and integrated linkage maps developed by inclusion of previously genotyped SSR and DArT markers. With the new linkage maps, we detected a total of 12 QTL for powdery mildew resistance in Shanghai3/Catbird x Naxos, of which eight were derived from Naxos. Previously reported QTL on chromosome arms 1AS and 2BL were more precisely mapped and the SNP markers enabled discovery of new QTL on 1AL, 2AL, 5AS and 5AL. In the Soru#1 x Naxos population, four QTL for powdery mildew resistance were detected, of which three had resistance from Naxos. This mapping verified the 1AS and 2AL QTL detected in Shanghai3/Catbird x Naxos, and identified a new QTL from Naxos on 2BL. In conclusion, the improved linkage maps with SNP markers enabled discovery of new resistance QTL and more precise mapping of previously known QTL. Moreover, the results were validated in an independent genetic background.     

Plasminogen, absorbed by Escherichia coli expressing curli or by Salmonella enteritidis expressing thin aggregative fimbriae, can be activated by simultaneously captured tissue-type plasminogen activator (t-PA)

Curli are fimbrial structures expressed by Escherichia coli that specifically interact with matrix proteins such as fibronectin and laminin. Similar structures are also expressed by Salmonella enteritidis and have been denoted thin aggregative fimbriae. Bacteria expressing curli and thin aggregative fimbriae were found to bind radiolabelled plasminogen as well as the tissue-type plasminogen activator (t-PA). By contrast, E. coli carrying a gene locus with an insertionally inactivated chromosomal curlin subunit were unable to bind the two human proteins. The purified subunit polypeptides of curli and thin aggregative fimbriae bound plasminogen and t-PA with high affinity (1 × 10⁸ to 2 × 10⁸ M^-1). The binding of plasminogen and t-PA to curli-expressing E. coli was only partially inhibited by fibronectin and laminin. Plasminogen absorbed from human plasma by curli-expressing E. coli was readily converted to plasmin by t-PA; both plasmin and t-PA were functionally active when bound to the bacteria. A simultaneous binding of fibrinolytic proteins and matrix proteins to fimbriae of E. coli and S. enteritidis could provide these pathogens with both adhesive and invasive properties.