Insect midgut structures and molecules as targets of plant‐derived protease inhibitors and lectins

The midgut of insects is involved in digestion, osmoregulation and immunity. Although several defensive strategies are present in this organ, its organization and function may be disturbed by some insecticidal agents, including bioactive proteins like lectins and protease inhibitors (PIs) from plants. PIs interfere with digestion, leading to poor nutrient absorption and decreasing amino acid bioavailability. Intake of PIs can delay development, cause deformities and reduce fertility. Ingestion of PIs may lead to changes in the set of proteases secreted in the insect gut, but this response is often insufficient and results in aggravation of the malnutrition status. Lectins are proteins that are able to interact with glycoconjugates, including those linked to cell surfaces. Their effects on the midgut include disruption of the peritrophic matrix, brush border and secretory cell layer; induction of apoptosis and oxidative stress; interference with nutrient absorption and transport proteins; and damaging effects on symbionts. In addition, lectins can cross the intestinal barrier and reach the hemolymph. The establishment of resistant insect populations due to selective pressure resulting from massive use of a bioactive protein is an actual possibility, but this can be minimized by the multiple mode‐of‐action of these proteins, mainly the lectins. © 2018 Society of Chemical Industry     

有机配体、竞争阳离子和pH对土壤中Zn分解的影响

A series of experiments were conducted to examine the interactive effects of an organic ligand, a competing cation, and pH on the dissolution of zinc （Zn） from three California soils, Maymen sandy loam, Merced clay, and Yolo clay loam. The concentrations of soluble Zn of the three soils were low in a background solution of Ca（NO3）2. Citric acid, a common organic ligand found in the rhizosphere, was effective in mobilizing Zn in these soils; its presence enhanced the concentration of Zn in soil solution by citrate forming a complex with Zn. The ability of Zn to form a complex with citric acid in the soil solution was dependent on the concentration of citric acid, pH, and the concentration of the competing cation Ca^2＋. The pH of the soil solution determined the extent of desorption of Zn in solid phase in the presence of citric acid. The amounts of Zn released from the solid phase were proportional to the concentration of citric acid and inversely proportional to the concentration of Ca（NO3）2 background solution, which supplied the competing cation Ca^2＋ for the formation of a complex with citrate. When the soil suspension was spiked with Zn, the adsorption of Zn by the soils was retarded by citric acid via the formation of the soluble Zn-citrate complex. The dissolution of Zn in the presence of citric acid was pH dependent in both adsorption and desorption processes.     

Resistance to <Emphasis Type="Italic">Meloidogyne incognita</Emphasis> expresses a hypersensitive-like response in <Emphasis Type="Italic">Coffea arabica</Emphasis>

Root-knot nematodes (RKN) are obligate parasite species of the genus Meloidogyne that cause great losses in Arabica coffee (Coffea arabica L.) plantations. Identification of resistant genotypes would facilitate the improvement of coffee varieties aiming at an environmental friendly and costless nematode control. In this work, the C. arabica genotype ‘UFV 408-28’ was found to be resistant to the most destructive RKN species M. incognita. Pathogenicity assays indicated that the highly aggressive populations of M. incognita races 1, 2 and 3 were not able to successfully reproduce on ‘UFV 408-28’ roots and displayed a low gall index (GI = 2). An average reduction of 87% reduction of the M. incognita population was observed on ‘UFV 408-28’ when compared to the susceptible cultivar ‘IAC 15’. By contrast, ‘UFV 408-28’ was susceptible to the related species M. exigua and M. paranaensis (GI = 5 and 4, respectively). Histological observations performed on sections of UFV408-28 roots infected with M. incognita race 1 showed that nematode infection could be blocked right after penetration or during migration and establishment stages, at 6 days, 7 days and 8 days after infection (DAI). Fluorescence and bright field microscopy observations showed that root cells surrounding the nematodes exhibited HR-like features such as accumulation of phenolic compounds and a necrotic cell aspect. In the susceptible ‘IAC 15’ roots, 6 DAI, feeding sites contained giant cells with a dense cytoplasm. Necrotic cells were never observed throughout the entire infection cycle. The HR-like phenotype observed in the ‘UFV 408-28’—M. incognita interaction suggests that the coffee resistance may be mediated by a R-gene based immunity system and may therefore provide new insights for understanding the molecular basis of RKN resistance in perennial crops.     

Batrachotoxin: chemistry and pharmacology

Batrachotoxin has been shown to be a pyrrolecarboxylic ester of a novel steroidal base with unique and selective actions on a variety of electrogenic membranes. The effects of batrachotoxin in neuromuscular preparations both pre- and postsynaptically, in nerve axons, in superior cervical ganglion, in heart Purkinje fibers, and in brain slices appear to be due to the selective and irreversible increase in permeability of membranes to sodium ions. The subsequent effects of this increase in Na(+) permeability evoked by batrachotoxin-such as membrane depolarization, enhanced spontaneous transmitter release, muscle contracture, and enhanced formation of cyclic AMP in brain slices-may be blocked reversibly by tetrodotoxin.     

Present status of the conservation of livestock genetic resources in Brazil

Brazil has various species of domestic animals, which developed from breeds brought by the Portuguese settlers soon after the discovery of the country. After being submitted to a long process of natural selection, these breeds present characteristics adapted to specific Brazilian environmental conditions, and are known as “criollo”, “local” or naturalized breeds. From the beginning of the 20th century, some exotic breeds, selected in temperate regions, have begun to be imported, and, although more productive, they do not have adaptive traits, such as resistance to disease and parasites found in the naturalized breeds. Even so, they gradually replaced the native breeds, to such an extent that the latter are in danger of extinction. To avoid further loss of this important genetic material, in 1983 the National Research Center for Genetic Resources and Biotechnology (Cenargen) of the Brazilian Agricultural Research Corporation (Embrapa) decided to include conservation of animal genetic resources among its priorities. The conservation activities have been conducted under the Brazilian Genetic Resources Network — Renargen, and is carried out by various research centres of Embrapa, universities and State research institutions, as well as by private farmers, with a single coordinator at national level, Cenargen. The in situ conservation of cattle, horses, buffaloes, donkeys, goats, sheep and pigs is being carried out by Conservation Nuclei, located in the animal's original habitat. Ex situ conservation is centred at the Brazilian Animal Germplasm Bank (AGB), kept at Cenargen. This is responsible for the storage of semen and embryos of various breeds of domestic animals threatened with extinction. Presently the AGB has almost 60,000 doses of semen and more than 250 embryos, as well as over 7000 DNA samples. An important challenge for this program is to increase awareness within the different segments of society in terms of the importance of the conservation of animal genetic resources. The development and evolution of Renargen and its efforts to facilitate the conservation of genetic resources of livestock in Brazil are described in this paper.     

Genetic characterization of Toxoplasma gondii isolates from pigs intended for human consumption in Brazil

This study genetically Toxoplasma gondii isolates obtained from pigs intended for human consumption in northeastern Brazil; multilocus PCR-RFLP and sequencing techniques were utilized. Bioassays were conducted using the brain and tongue of 20 pig heads purchased at butcher shops in the city of Ilheus, Bahia, Brazil. Overall, 11 T. gondii isolates designated TgPgBr06-16 were identified. Application of multilocus PCR-RFLP with seven molecular markers (SAG1, SAG2, SAG3, BTUB, C22-8, PK1 and Apico) identified six different genotypes. Isolates TgPgBr 06, 08, 11, 12, 14 and 15 were indistinguishable by this technique, forming a single genotype; the remaining isolates were characterized as distinct genotypes. However, when five genetic markers (SAG1, SAG2, SAG3, BTUB and c22-8) were employed in multilocus PCR-sequencing, all eleven strains of T. gondii were shown to be different. All isolates differed from Type I, II and III clonal genotypes using both genotyping techniques. These results demonstrate that the multilocus PCR-RFLP assay underestimated the true diversity of the T. gondii population in this study. Thus, DNA sequencing is the preferred technique to infer the genetic diversity and population structure of T. gondii strains from Brazil. Moreover, it is necessary to develop new molecular markers to group and characterize atypical T. gondii isolates from South America.     

Mesquite pod meal as an additive increases milk total solids,lactose, fat and protein content in dairy cows

The objective was to evaluate the intake, digestibility, milk yield and composition of cows fed mesquite pod meal (MPM). Five crossbred dairy cows, with an average body weight of 450?±?5 kg and producing 10?±?1 kg of milk/day were distributed in a 5?×?5 Latin square arrangement with five periods of 20 days each, comprised of 15 days for adaptation to the experimental diets (T1?=?0%, T2?=?1.5%, T3?=?3.0%, T4?=?4.5% and T5?=?6.0% MPM) and 5 days for data collection. Variables were assessed by analysis of variance and regression at P?<?0.01 and P?<?0.05 of significance, using the Student’s test. Animals were kept on pastures and the concentrates were provided at 6 kg/animal divided in two meals per day. The inclusion of 3.0% mesquite pod meal did not affect the intake, digestibility of nutrients and milk yield, but it changed milk composition. The dietary inclusion of 3.0% mesquite pod meal as a palatability enhancer increases the percentage of milk solids, lactose, fat and protein. Therefore, mesquite pod meal can be included in diets for dairy cows to improve the nutritive value of milk.

     

Evaluating irrigation performance in a Mediterranean environment

Assessment of irrigation performance is a prerequisite for improving water use in the agricultural sector to respond to perceived water scarcity. Between 1996 and 2000, we conducted a comprehensive assessment of the performance of the Genil–Cabra irrigation scheme (GCIS) located in Andalusia, southern Spain. The area has about 7,000 ha of irrigated lands distributed in 843 parcels and devoted to a diverse crop mix, with cereals, sunflower, cotton, garlic and olive trees as principal crops. Irrigation is on demand from a pressurized system and hand-moved sprinkler irrigation is the most popular application method. Six performance indicators were used to assess the physical and economic performance of irrigation water use and management in the GCIS, using parcel water-use records and a simulation model. The model simulates the water-balance processes on every field and computes an optimal irrigation schedule, which is then checked against actual schedules. Among the performance indicators, the average irrigation water supply:demand ratio (the ratio of measured irrigation supply to the simulated optimum demand) varied among years from 0.45 to 0.64, indicating that the area is under deficit irrigation. When rainfall was included, the supply:demand ratio increased up to 0.87 in one year, although it was only 0.72 in the driest year, showing that farmers did not fully compensate for the low rainfall with sufficient irrigation water. Nevertheless, farmers in the area made an efficient use of rainfall, as indicated by the relatively high values (0.72–0.83) for the ratio of actual:attainable crop yields. Water productivity (WP) in the GCIS oscillated between 0.72 €/m³ and 1.99 €/m³ during the 4 years and averaged 1.42 €/m³ of water supplied for irrigation, while the irrigation water productivity (IWP) averaged 0.63 €/m³ for the period studied. WP is higher than IWP because WP includes production generated by rainfall, while IWP includes only the production generated by irrigation.Communicated by A. Kassam