Influence of abiotic factors,inoculum source,and cultivar susceptibility on the potato tuber blemish diseases black dot (Colletotrichum coccodes) and silver scurf (Helminthosporium solani)

Black dot and silver scurf are potato blemish diseases whose economic impact has increased in recent years. Because their symptomatology on tubers is visually similar, disease assessment does not usually differentiate between the two pathogens, which share the same ecological niche. The epidemiology of black dot has been extensively studied, especially in the UK, but the factors that influence silver scurf have been less investigated. In this study, the influence of cultivar, source of inoculum, and environmental conditions on both diseases was studied in field trials over a three-year period (2016–2018) in Switzerland. Planting minitubers did not prevent either disease in daughter tubers, indicating the contribution of soil as an inoculum reservoir. An arbitrary threshold of Colletotrichum coccodes soil inoculum could be set to discriminate between low and high disease risk. For the first time, Helminthosporium solani DNA was detected in stolons, and infections appeared earlier in stolons than in tubers. H. solani stolon and tuber infections usually appeared later in the season than those of C. coccodes. Black dot severity correlated positively with precipitation, while silver scurf severity correlated positively with temperature. Table potato cultivars commonly grown in Switzerland exhibited significant differences in susceptibility to both diseases, and cultivars with low susceptibility to both silver scurf and black dot were identified. These results gave new insights into understanding the factors driving the epidemiology of potato blemish diseases and may contribute to building a risk assessment scheme to manage both diseases simultaneously.     

Cloning, expression, and characterization of the MSP1a and MSP1b recombinant proteins from PR1 Anaplasma marginale strain, Brazil

The Anaplasma marginale is a bacterium that has obligate intraerythrocytic multiplication in cattle causing important economic loss. The A. marginale major surface protein 1 (MSP1) complex, heterodimer composed of MSP1a and MSP1b, has been identified as adhesins for bovine erythrocytes. The objectives of this study were to sequences the msp1β gene and produce and characterize recombinant MSP1a and MSP1b from a Brazilian strain of A. marginale, PR1. The msp1α and msp1β genes from the PR1 strain were cloned and expressed in E. coli BL21 Star using the vectors pET102 and pET101/D-TOPO. Antibodies were produced against the recombinant proteins and were shown to react with rMSP1a and rMSP1b demonstrating a molecular mass of 70 kDa to 105 kDa and 100 kDa, respectively for these proteins. Bovine erythrocytes were agglutinated by BL21/rMSP1a and BL21/rMSP1b and, this agglutination was inhibited by the presence of the IgY anti-rMSP1a, confirming the adhesion function of these proteins. Additionally, using the IgY anti-rMSP1a and rMSP1b in a IFI, the presence of rMSP1a and rMSP1b was confirmed on the outer membrane of the recombinant E. coli BL21. Our results show that the msp1β gene from the PR1 strain has both the conserved region and contain the defined polymorphism regions previously described for other strains of A. marginale. The results from this study confirm adhesive functions for rMSP1a and rMSP1b from PR1 strain in bovine erythrocytes invasion.     

Intron removal requires proofreading of U2AF/3' splice site recognition by DEK

Discrimination between splice sites and similar, nonsplice sequences is essential for correct intron removal and messenger RNA formation in eukaryotes. The 65- and 35-kD subunits of the splicing factor U2AF, U2AF65 and U2AF35, recognize, respectively, the pyrimidine-rich tract and the conserved terminal AG present at metazoan 3' splice sites. We report that DEK, a chromatin- and RNA-associated protein mutated or overexpressed in certain cancers, enforces 3' splice site discrimination by U2AF. DEK phosphorylated at serines 19 and 32 associates with U2AF35, facilitates the U2AF35-AG interaction and prevents binding of U2AF65 to pyrimidine tracts not followed by AG. DEK and its phosphorylation are required for intron removal, but not for splicing complex assembly, which indicates that proofreading of early 3' splice site recognition influences catalytic activation of the spliceosome.     

Epochal evolution shapes the phylodynamics of interpandemic influenza A (H3N2) in humans

Human influenza A (subtype H3N2) is characterized genetically by the limited standing diversity of its hemagglutinin and antigenically by clusters that emerge and replace each other within 2 to 8 years. By introducing an epidemiological model that allows for differences between the genetic and antigenic properties of the virus's hemagglutinin, we show that these patterns can arise from cluster-specific immunity alone. Central to the formulation is a genotype-to-phenotype mapping, based on neutral networks, with antigenic phenotypes, not genotypes, determining the degree of strain cross-immunity. The model parsimoniously explains well-known, as well as previously unremarked, features of interpandemic influenza dynamics and evolution. It captures the observed boom-and-bust pattern of viral evolution, with periods of antigenic stasis during which genetic diversity grows, and with episodic contraction of this diversity during cluster transitions.     

Analysis of genetic diversity in Agave tequilana var. Azul using RAPD markers

By federal law in Mexico, A. tequilana Weber var. Azul is the only variety of agave permitted for the production of any tequila. Our objective was to assay levels of genetic variation in field populations of A. tequilana var. Azul using randomly amplified polymorphic DNA (RAPD) markers. Ten plants were collected from each of four different fields, with two fields being located in each of two principal regions of Mexico for the cultivation of A. tequilana var. Azul. The two regions are separated geographically by approximately 100km. Genetic relationships between A. tequilana var. Azul and two other varieties of A. tequilana Weber, ‘Chato’ and ‘Siguin’, were also investigated using RAPDs. Among the three varieties, 19 decamer primers produced 130 markers, of which 20 (15.4%) were polymorphic betweenA. tequilana var. Chato and A. tequilana var. Siguin. The results of RAPD analysis suggest that A. tequilana var. Siguin is more closely related to A. tequilana var. Azul than is A. tequilana var. Chato. Among the 40 field selections of A. tequilana var. Azul, only 1 of124 RAPD products (0.8%) was polymorphic and 39 of 40 plants were completely isogenic. This is one of the lowest levels of polymorphism detected to date for the analysis of a crop species, and is proposed to be the result of the promotion of a single conserved genotype over many years due to an exclusive reliance on vegetative propagation for the production of new planting materials. The significance of these results is discussed in relation to breeding programs focused on the improvement of A. tequilana var. Azul. This revised version was published online in July 2006 with corrections to the Cover Date.     

Delta-viniferin,a resveratrol dehydrodimer: one of the major stilbenes synthesized by stressed grapevine leaves

Delta-viniferin is a resveratrol dehydrodimer, an isomer of epsilon-viniferin. This compound has been reported as a molecule produced in vitro by the oxidative dimerization of resveratrol by plant peroxidases or fungal laccases. It was also recently identified in wines and in grape cell cultures. We have now identified this dimer by NMR, high-performance liquid chromatography-diode array detection (HPLC-DAD), and HPLC-mass spectrometry (MS) in grapevine leaves infected by Plasmopara viticola (downy mildew) or UV-C irradiated. Its concentration was higher than that of epsilon-viniferin and constitutes one of the most important phytoalexins derived from resveratrol.     

Effects of vegetation,urban density,building height,and atmospheric conditions on local temperatures and thermal comfort

This paper shows the effects of several variables, which co-cause the Urban Heat Island effect on temperature distribution and outdoor thermal comfort (by using the Predicted Mean Vote, PMV) on dense urban environments. The study was conducted by means of a three-dimensional microclimate model, ENVI-met 3.1, which forecasts the microclimatic changes within urban environments. The effects of building density (% of built area) and canyon effect (building height) on potential temperature, mean radiant temperature, and Predicted Mean Vote distribution are quantified. The influence of several types of green areas (vegetation on the ground and on roofs) on temperature mitigation and on comfort improvements is investigated for different atmospheric conditions and latitudes in a Mediterranean climate. The research quantifies the effects of the variables investigated on temperature distributions and in determining outdoor comfort conditions. Vegetation on the ground and on roofs mitigates summer temperatures, decreases the indoor cooling load demand, and improves outdoor comfort. The results of the study demonstrate that density and height of buildings in a city area influence potential temperature, mean radiant temperature, and Predicted Mean Vote distribution; for most of the cases examined higher density causes higher temperatures and with taller buildings vegetation has higher cooling effects. Considering the cooling effect of vegetation, a difference can be noticed depending on the amount of green areas and vegetation type. The results of this study show also that vegetation is more effective with higher temperatures and lower relative humidity values in mitigating potential temperatures, mean radiant temperatures, and PMV and in decreasing the cooling load demand.