Differentiation of citrus tristeza closterovirus (CTV) isolates by single-strand conformation polymorphism analysis of the coat protein gene

Citrus tristeza closterovirus (CTV) isolates of several geographical origins were compared for variations in their coat protein (CP) gene by analysis of single-strand conformation polymorphism (SSCP). The CP gene of 17 isolates was reverse transcribed, amplified by polymerase chain reaction (PCR), and 22 clones were inserted into a plasmid vector. These clones were sequenced and found to have between 91.7% and 99.8% sequence homology. Clones were amplified and the PCR products denatured and compared by SSCP analysis in 8% polyacrylamide gels. Using two different electrophoretic conditions, the patterns were different for 16 or 17 clones. Four pairs of clones (T36/T66, P1/Q2, 03/8Q, and E1/E2) differing by 10, 2, 1 and 1 nucleotides, respectively, could not be distinguished using either condition. When these clones were compared by SSCP after digestion with Eco91I (BstEII) three of the pairs (T36/T66, P1/Q2, and 03/8Q) could be differentiated, whereas the clones E1 and E2 (differing by 1 nucleotide) remained indistinguishable. Thus, SSCP analysis combining two electrophoretic conditions and restriction of eight clones with Eco91I allowed discrimination between 21 of the 22 CP gene clones selected. SSCP analysis may provide a procedure to identify and differentiate CTV isolates based on comparisons of several genes or gene regions. It is rapid and cheap and may drastically reduce the amount of sequencing necessary for accurate comparisons.     

Sensitivity to Lysostaphin as a Criterion for the Identification of Staphylococci from Animal Origin

A total of 195 Gram positive, catalase positive cocci, isolated from ovine mastitis, abscesses in slaughtered animals and parasitic pulmonary lesions in lambs were tested for glucose fermentation, anaerobic growth in thioglycollate medium, coagulase production and susceptibility to the lytic action of lysostaphin. On the basis of lysostaphin sensitivity, 192 strains were classified as staphylococci. The number of cultures able to produce acid anaerobically from glucose, or giving a positive result in the test of Evans and Kloos was lower. A good correlation among these three tests was not observed. Ninety-seven of the strains tested gave a positive coagulase reaction. Sensitivity to lysostaphin could not be used as a criterion for the differentiation of coagulase positive and coagulase negative strains. The turbidimetric method employed for the assessment of lysostaphin sensitivity is discussed.     

Insecticide susceptibility status in Mexican populations of Stegomyia aegypti (= Aedes aegypti): a nationwide assessment

In Mexico, mosquito vector‐borne diseases are of public health concern as a result of their impact on human morbidity and mortality. The use of insecticides against adult mosquitoes is one of the most common ways of controlling mosquito population densities. However, the use of these compounds has resulted in the development of insecticide resistance. The aim of this study was to estimate susceptibility to six pyrethroids, two carbamates and two organophosphates in Mexican populations of Stegomyia aegypti (Linnaeus, 1762) (= Aedes aegypti) (Diptera: Culicidae) mosquitoes. Bottle insecticide susceptibility tests, with 1 h exposure, were performed on adult mosquitoes from 75 localities across 28 states. At 30 min of exposure, the proportion of fallen mosquitoes was recorded. After 60 min of exposure, mosquitoes were recovered in non‐treated containers and mortality was determined at 24 h after the set‐up of the experiment. In general, the carbamate insecticides represented the most effective group in terms of the proportion of mosquitoes fallen at 30 min (72–100%) and 24‐h mortality (97–100%). High and widespread resistance to pyrethroids Types I and II and, to a lesser extent, to organophosphates was observed. Insecticide susceptibility among and within states was highly variable.     

Hindlimb morphology and locomotor performance in waders: an evolutionary approach

Locomotion performance (measured as stride frequency and stride length) was studied in 16 species of waders. Differences in hindlimb morphology (osteology and myology) were analysed among species. Evolutionary changes in both locomotion and morphological variables were analysed using comparative methods revealing the existence of some ecomorphological patterns relating these two sets of characters. Evolutionary changes in stride frequency were correlated with changes in the muscles M. iliotibialis cranialis, M. iliotibiales lateralis and M. gastrocnemius, whereas changes in stride length showed correlated evolution with changes in the length of distal segments of the leg. We identify two different evolutionary strategies in locomotion of waders. One is a change in distal leg segments (skeletal system), an adaptive modification that increases stride length; the second is a change in the skeletal-muscular system, providing an increase in muscular performance (force or speed of contraction) in several muscles, and is an adaptation that increases stride frequency.     

Abscisic acid is involved in the response of grape (Vitis vinifera L.) cv. Malbec leaf tissues to ultraviolet-B radiation by enhancing ultraviolet-absorbing compounds, antioxidant enzymes and membrane sterols

We investigated the interactions of abscisic acid (ABA) in the responses of grape leaf tissues to contrasting ultraviolet (UV)-B treatments. One-year-old field-grown plants of Vitis vinifera L. were exposed to photosynthetically active radiation (PAR) where solar UV-B was eliminated by using polyester filters, or where PAR was supplemented with UV-B irradiation. Treatments combinations included weekly foliar sprays of ABA or a water control. The levels of UV-B absorbing flavonols, quercetin and kaempferol were significantly decreased by filtering out UV-B, while applied ABA increased their content. Concentration of two hydroxycinnamic acids, caffeic and ferulic acids, were also increased by ABA, but not affected by plus UV-B (+UV-B) treatments. Levels of carotenoids and activities of the antioxidant enzymes, catalase, ascorbate peroxidase and peroxidase were elevated by +ABA treatments, but only if +UV-B was given. Cell membrane β -sitosterol was enhanced by ABA independently of +UV-B. Changes in photoprotective compounds, antioxidant enzymatic activities and sterols were correlated with lessened membrane harm by UV-B, as assessed by ion leakage. Oxidative damage expressed as malondialdehyde content was increased under +UV-B treatments. Our results suggest that the defence system of grape leaf tissues against UV-B is activated by UV-B irradiation with ABA acting downstream in the signalling pathway.     

Plant species richness as the main driver of moth metacommunities

1. Ecologists have recognised several factors that may explain the distribution of species in a metacommunity. These factors may be related to the dispersal of individuals among the patches and environmental conditions. 2. Here, we attempted to determine which of the four different metacommunity frameworks (patch dynamics, mass effect, neutral processes, and species sorting) explain the distribution of Arctiinae moths in Brazilian savanna areas with different tree species richness. 3. The Arctiinae moths were categorised as habitat specialists or generalists, common or rare, and belonging to the tribes Arctiini and Lithosiini. We hypothesized that environmental variables best explain the abundance and occurrence of habitat specialist species, common species, and members of Lithosiini; whereas spatial processes are more closely related to habitat generalists, rare species, and members of Arctiini. 4. Contrary to our expectations, we found that the species sorting (mainly dictated by the species richness of trees) best explained the variation in abundance and occurrence of the majority of species groups. Spatial processes (more related to patch dynamics, mass effect, and neutral), although they were significantly related to some species groups, were not strong enough to explain the distribution of these species in the study area. 5. The plant species richness was the most important environmental condition, related to moth species niches. Therefore, species sorting best explained the distribution of the species of Arctiinae in the Brazilian savanna.     

Niche modelling of the Chilean recluse spider Loxosceles laeta and araneophagic spitting spider Scytodes globula and risk for loxoscelism in Chile

In Chile, all necrotic arachnidism is attributed to the Chilean recluse spider Loxosceles laeta (Nicolet) (Araneae: Sicariidae). It is predated by the spitting spider Scytodes globula (Nicolet) (Araneae: Scytodidae). The biology of each of these species is not well known and it is important to clarify their distributions. The aims of this study are to elucidate the variables involved in the niches of both species based on environmental and human footprint variables, and to construct geographic maps that will be useful in estimating potential distributions and in defining a map of estimated risk for loxoscelism in Chile. Loxosceles laeta was found to be associated with high temperatures and low rates of precipitation, whereas although S. globula was also associated with high temperatures, its distribution was associated with a higher level of precipitation. The main variable associated with the distribution of L. laeta was the human footprint (48.6%), which suggests that this is a highly invasive species. Similarly to other species, the distribution of L. laeta reaches its southern limit at the Los Lagos region in Chile, which coincides with high levels of precipitation and low temperatures. The potential distribution of L. laeta in Chile corresponds to the distribution of cases of loxoscelism.     

House Sparrows Passer domesticus with larger uropygial glands show reduced feather wear

This study assesses whether uropygial gland size is related to improved feather quality. To address this question, I analysed the relationship between uropygial gland size and feather wear in the House Sparrow Passer domesticus. The results show that birds with larger uropygial glands had less worn feathers, suggesting that uropygial gland secretions improve feather resistance to abrasion.     

The incidence and distribution of viruses infecting lettuce, cultivated Brassica and associated natural vegetation in Spain

A virus survey was conducted during the spring and autumn of 2001 and 2002 to determine the presence, prevalence and distribution in Spain of the viruses that are most commonly found infecting lettuce and Brassica worldwide. Crop plants showing virus symptoms from the principal lettuce and Brassica-growing regions of Spain, and some samples of the annual and perennial flora nearby, were tested by enzyme-linked immunosorbent assays using specific commercial antibodies against the following viruses: Alfalfa mosaic virus (AMV), Broad bean wilt virus 1 (BBWV-1), Beet western yellows virus (BWYV), Cauliflower mosaic virus (CaMV), Cucumber mosaic virus (CMV), Lettuce mosaic virus (LMV), Pea seed-borne mosaic virus (PSbMV), Turnip mosaic virus (TuMV) and Tomato spotted wilt virus (TSWV). Samples were also tested with a Potyvirus genus antibody. Virus incidence was much lower in spring than in autumn, especially in 2001. In spring 2002, CMV and LMV were the most prevalent viruses in lettuce, while CaMV was the most important virus present in Brassica crops grown in Navarra, followed by CMV and BWYV. In the autumn, the spectrum of viruses was different; potyviruses were widespread in lettuce grown in Madrid, but TSWV and BWYV were predominant in the Murcia region. The prevalent Potyvirus detected in lettuce fields was LMV, but none of the samples collected were positive for PSbMV or TuMV. In Brassica crops, TSWV was the most abundant in autumn-sown crops, especially in the Navarra region. All of the viruses present in lettuce and Brassica were also frequently detected in their associated natural vegetation at the same time, suggesting that they probably play an important role as virus reservoirs. Sonchus spp. were particularly common and were frequently infected with CMV, LMV and BWYV. Another common species, Chenopodium album, was often infected with TSWV and BWYV. Multiple infections were common, especially in non-crop plants, and the most common combination was BWYV and TSWV. The role of weeds in the epidemiology of viruses that infect lettuce and Brassica crops in Spain is discussed.     

The Role of Acidocalcisomes in Parasitic Protists1

ABSTRACT. Acidocalcisomes are acidic organelles with a high concentration of phosphorus present as pyrophosphate (PP_i) and polyphosphate (poly P) complexed with calcium and other cations. The acidocalcisome membrane contains a number of pumps (Ca²⁺‐ATPase, V‐H⁺‐ATPase, H⁺‐PPase), exchangers (Na⁺/H⁺, Ca²⁺/H⁺), and channels (aquaporins), while its matrix contains enzymes related to PP_i and poly P metabolism. Acidocalcisomes have been observed in pathogenic, as well as non‐pathogenic prokaryotes and eukaryotes, e.g. Chlamydomonas reinhardtii, and Dictyostelium discoideum. Some of the potential functions of the acidocalcisome are the storage of cations and phosphorus, the participation of phosphorus in PP_i and poly P metabolism, calcium homeostasis, maintenance of intracellular pH homeostasis, and osmoregulation. In addition, acidocalcisomes resemble lysosome‐related organelles (LRO) from mammalian cells in many of their properties. For example, we found that platelet dense granules, which are LROs, are very similar to acidocalcisomes. They share a similar size, acidic properties, and both contain PP_i, poly P, and calcium. Recent work that indicates that they also share the system for targeting of their membrane proteins through adaptor protein 3 reinforces this concept. The fact that acidocalcisomes interact with other organelles in parasitic protists, e.g. the contractile vacuole in Trypanosoma cruzi, and other vacuoles observed in Toxoplasma gondii, suggests that these cellular compartments may be associated with the endosomal/lysosomal pathway.