Rapid sequence modification in the highly polymorphic region (HPR) of the hemagglutinin gene of the infectious salmon anaemia virus (ISAV) suggests intra-segmental template switching recombination

The ISAV has a genome composed of eight segments of (–)ssRNA, segment 6 codes for the hemagglutinin–esterase protein, and has the most variable region of the genome, the highly polymorphic region (HPR), which is unique among orthomyxoviruses. The HPR has been associated with virulence, infectivity and pathogenicity. The full length of the HPR is called HPR0 and the strain with this HPR is avirulent, in contrast to strains with deleted HPR that are virulent to varying degrees. The molecular mechanism that gives rise to the different HPRs remains unclear. Here, we studied in vitro the evolution of reassortant recombinant ISAV (rISAV) in Atlantic salmon head kidney (ASK) cells. To this end, we rescued and cultivated a set of rISAV with different segment 6-HPR genotypes using a reverse genetics system and then sequencing HPR regions of the viruses. Our results show rapid multiple recombination events in ISAV, with sequence insertions and deletions in the HPR, indicating a dynamic process. Inserted sequences can be found in four segments of the ISAV genome (segments 1, 5, 6, and 8). The results suggest intra-segmental heterologous recombination, probably by class I and class II template switching, similar to the proposed segment 5 recombination mechanism.     

Susceptibility of Caligus rogercresseyi collected from the native fish species Eleginops maclovinus (Cuvier) to antiparasitics applied by immersion

A major challenge for Chilean salmon farming is infestation by the ectoparasite Caligus rogercresseyi. In addition, there is evidence that a loss of chemotherapeutic treatment efficacy against important fish pathogens is occurring in salmon farming, including antiparasitic efficacy. Currently, there are known techniques that allow the determination of the susceptibility profile of parasites to antiparasitic treatment. However, there is scarce information about both threshold values and categorization of antiparasitic susceptibility for C. rogercresseyi. Bioassay technique allowed the determination of both mean values and the natural variation of EC50%, which were contrasted with available susceptibility thresholds. Results allowed to determine that parasites from the native fish host, Eleginops maclovinus, are susceptible to azamethiphos, deltamethrin and cypermethrin treatments, showing a high susceptibility profile to antiparasitics.     

Decomposition processes in coastal lagoons and their implications for the assessment of ecological health

1. Aside from structural indicators, functional indicators have been suggested as a tool for assessing the health of transitional water ecosystems. The aim of this study was to assess the potential for the use of plant litter decomposition as a functional indicator of ecosystem health in coastal lagoons.
2. A field experiment was conducted to assess the decomposition rate of Ruppia maritima enclosed in coarse and fine mesh litterbags and incubated in 10 Mediterranean coastal lagoons that conform to a gradient of ecological status produced by anthropogenic impacts as determined by a structural quality index.
3. The microbial decomposition rate in fine mesh litterbags increased linearly along the ecological gradient. However, this relationship was not observed for the overall decomposition rate in coarse mesh bags.
4. Decomposition rates in coarse mesh bags were negatively related to macroinvertebrate diversity, indicating that, in transitional habitats, such as coastal lagoons, high biodiversity is not a prerequisite for successful ecosystem functioning.
5. The results suggest that functional indicators, such as the microbial litter decomposition process, should be used in addition to structural ones to detect anthropogenic‐derived environmental perturbations in coastal lagoons.

     

Potato germplasm development for warm climates: genetic enhancement of tolerance to heat stress

Complex potato hybrids were derived through unilateral sexual polyploidization between Solanum tuberosum cv. Atlantic and 11 diploid hybrids that produced 2n pollen through co-orientation of second division spindles. The hybrids represented the following genomic compositions: TAPB, TAPC, and TAPM where T = S. tuberosum, A = S. andigena, P = S. phureja, B = S. berthaultii, C = S. chacoense, and M = S. microdontum. The B, C, and M components of the hybrids had been selected from heat tolerant accessions. The heat tolerance and agronomic performance of the hybrids were assessed under both controlled environments and field tests. The hybrids exhibited good tuberization potential (tuber number, tuber weight and percent plants producing tubers) under heat stress conditions in controlled environments. Under severe heat stress conditions in the field in Israel, many of the hybrids tuberized when Atlantic failed to produce any tubers at all. Under more moderate heat stress in Virginia, the complex hybrids exhibited total tuber yield not significantly different from Atlantic, although the tuber set per plant was greater. However, the complex hybrids were more tolerant to heat necrosis and hollow heart than Atlantic. Total glycoalkaloids in field-grown tubers did not exceed the acceptable limit for 13 of 26 selections examined. This revised version was published online in July 2006 with corrections to the Cover Date.     

Significant increases in pulping efficiency in C4H-F5H-transformed poplars: improved chemical savings and reduced environmental toxins

The gene encoding ferulate 5-hydroxylase (F5H) was overexpressed in poplar (Populus tremula x Populus alba) using the cinnamate-4-hydroxylase (C4H) promoter to drive expression specifically in cells involved in the lignin biosynthetic pathway and was shown to significantly alter the mole percentage of syringyl subunits in the lignin, as determined by thioacidolysis. Analysis of poplar transformed with a C4H-F5H construct demonstrated significant increases in chemical (kraft) pulping efficiency from greenhouse-grown trees. Compared to wild-type wood, decreases of 23 kappa units and increases of >20 ISO brightness units were observed in trees exhibiting high syringyl monomer concentrations. These changes were associated with no significant modification in total lignin content and no observed phenotypic differences. C4H-F5H-transformed trees could increase pulp throughputs at mills by >60% while concurrently decreasing chemicals employed during processing (chemical pulping and bleaching) and, consequently, the amount of deleterious byproducts released into the environment.     

Aroma extract dilution analysis. Precision and optimal experimental design

The odor thresholds of 12 different compounds have been determined in an AEDA experiment using a panel composed of 8 individuals. Only in one case is the distribution of thresholds among judges significantly different from the log-normal. The cause of that departure from normality seems to be a cross adaptation rather than anosmia. The standard deviations (SD) range from 2(0.7) to 2(4.1), with 2(1.8) as average. If the AEDA is carried out at a dilution rate, R, and dilution R(P) (where P = 0, 1, 2.) is the last one at which a compound was detected by a judge, the flavor dilution (FD) factor that should be provided for that judge is R(P+0.5). In the case where several judges carry out the AEDA, the FD for a given compound should be the geometric mean of the FD provided by all the judges. The SD of the distribution of FDs is related to that of the distribution of odor thresholds, but is strongly influenced by the dilution rate, R, being higher with higher R values. The relationship between both SDs can be used to determine the expected precision (measured as the geometric length of the 95% confidence interval) of the result of an AEDA experiment as a function of the dilution rate, the number of judges, and the SD of the distribution of thresholds. Different simulations have shown that in most cases, a dilution rate of 10 is the best option, and that lower dilution rates are advantageous only if the analyzed solution contains compounds with a very narrow distribution of thresholds.     

Partial replacement of Fe(o,o‐EDDHA) by humic substances for Fe nutrition and fruit quality of citrus

The most widely used Iron (Fe) fertilizer in calcareous soils is the synthetic chelate Fe(o,o‐EDDHA). However, humic substances are occasionally combined with Fe chelates in drip irrigation systems in order to lower costs. We investigated the effect of various mixtures of Fe(o,o‐EDDHA) and a commercially available humic substance on Fe availability in a calcareous soil from Murcia, Spain (in vitro experiment) and on leaf Fe content and fruit‐quality attributes of Citrus macrophylla (field experiment). In the in vitro experiment, a calcareous soil was incubated for 15 d with solutions of sole Fe(o,o‐EDDHA) and humic substance and of a mixture of humic substance and Fe(o,o‐EDDHA) to determine the dynamics of available Fe. While the mixture did not significantly increase the available soil Fe, it did decrease the rate of Fe retention in the surface soil compared to sole Fe(o,o‐EDDHA). In the field experiment, the substitution in the application solution of 67% of Fe(o,o‐EDDHA) by commercial humic substance increased leaf P in lemon trees from 0.19% with sole Fe(o,o‐EDDHA) to 0.30% and leaf Fe from 94 mg kg^–1 to 115 mg kg^–1. Some quality parameters like vitamin C content and peel thickness were also improved with a partial substitution of Fe(o,o‐EDDHA) by humic substances. We conclude that a partial substitution of commercial Fe chelates by humic substance can improve crop Fe uptake and may thus be economically attractive. The underlying physiological mechanisms and ecological implications require further studies.     

Volatile compounds in Hispánico cheese manufactured using a mesophilic starter,a thermophilic starter,and bacteriocin-producing Lactococcus lactis subsp. lactis INIA 415

The effect of the addition of Lactococcus lactis subsp. lactis INIA 415, a strain harboring the structural genes of nisin Z and lacticin 481, on the formation of volatile compounds in Hispánico cheese manufactured with a mesophilic starter or with the mesophilic starter and a thermophilic starter was investigated. Addition of bacteriocin-producing L. lactis subsp. lactis INIA 415 to milk enhanced the formation of 2-methyl-propanal, 2-methylbutanal, 3-methylbutanal, 2-methyl-1-propanol, 3-methyl-1-butanol, 1-octanol, 2-butanone, and 2,3-butanedione. On the other hand, addition of thermophilic starter enhanced the formation of acetaldehyde, ethanol, 3-methyl-2-buten-1-ol, ethyl butanoate, ethyl hexanoate, 2-butanone, and 2,3-butanedione in Hispánico cheese. Stepwise discriminant analysis using the relative abundances of volatile compounds classified cheeses by type of starter, with function 1 related to thermophilic starter and function 2 to bacteriocin producer.     

Element distribution of some soils of continental Chile and the Antarctic peninsula. Projection to atmospheric pollution

Water, Air, & Soil Pollution - The elemental content of some soils of continental Chile and the Antarctic Peninsula are reported. The elements: Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb were...