Prospects for strain improvement in entomopathogenic fungi

The deployment of entomopathogenic fungi for the control of insect pests offers an environmentally-acceptable strategy. Major obstacles to their application include variability in effectiveness due to uncontrolled environmental parameters (temperature, humidity) and development of suitable formulation techniques. Strains differ considerably in genetic ability to cause mortality and to spread within populations. Pathogenicity is the result of the interaction of numerous individual traits determining germination and penetration, followed by successful growth within the target host, which is a prerequisite for induction of mortality. No effective singlegene determined toxin has been reported for entomopathogenic fungi, but the application of gene cloning techniques for specific proteases is a likely future development. Genetic manipulation techniques, designed to recombine complex traits associated with pathogenicity via the parasexual cycle, are described here in relation to successful steps achieved in strain improvement programmes which involve: (a) Verticillium lecanii (Zimm.) Viegas against the glasshouse whitefly: Trialeurodes vaporariorum and the aphid Macrosiphoniella sanborni; (b) Metarhizium anisopliae (Metsch.) Sorokin against the rice brown planthopper Nilaparvata lugens.     

Dietary triorganotins affect lymphatic tissues and blood composition of mice

Ph₃SnCl, Ph₃SnAc (Brestan), Cy₃SnOH (Plictran), and (Bu₃Sn)₂O (TBTO) markedly reduce the weight of the spleen and the gain in body weight of young mice feeding for 7 days on diets containing 260 μequiv organotin/kg diet. With mature mice feeding for 4 days on diets containing 780 μequiv organotin/kg, these compounds result in a loss in spleen weight and body weight and an alteration in the blood composition (reduction in lymphocytes and total leucocytes and an increase in erythrocytes, hemoglobin level, and hematocrit value). Four other organotins, [(PhCMe₂CH₂)₃Sn]₂O (Vendex), PhSnCl₂, Ph₂SnCl₂, and Ph₄Sn, are much less toxic based on these parameters. Poisoning by these dietary triorganotins was not related to cerebral edema or alterations in adrenal epinephrine level, liver nonprotein -SH groups, or the activity of digestive enzymes (intestine and stomach proteases and intestine amylase and invertase). The most sensitive indices of triorganotin toxicity appear to be those associated with changes in the lymphatic tissues and blood composition.     

Vagococcus salmoninarum I—A chronic coldwater streptococcosis in broodstock brook trout (Salvelinus fontinalis) in Wisconsin,USA

In 2018, Vagococcus salmoninarum was isolated from two lots of broodstock “coaster” brook trout (Salvelinus fontinalis) containing ~1,500 fish at the Iron River National Fish Hatchery, at which time it was identified as the causative agent of a chronic coldwater streptococcosis epizootic. Clinical signs included exophthalmia, lethargy, erratic swimming and loss of equilibrium. Female fish experienced disproportionately higher morbidity and mortality than male co-inhabitants, and routinely retained eggs following spawning. The most consistent gross clinical sign was heart pallor and turbid pericardial effusion. An attempted treatment using florfenicol was ineffective at halting the epizootic, which spanned more than a year and resulted in >50% mortality before remaining fish were culled. As there is no previous documentation of V. salmoninarum at this hatchery or in this species, it is still unclear what circumstances led to this epizootic. The inability to treat this chronic disease led to the loss of valuable broodstock, hampering ongoing fishery conservation efforts in the Great Lakes Basin.     

Vagococcus salmoninarum II—qPCR,tropism and egg-associated transmission

Vagococcus salmoninarum was identified as the causative agent of a chronic epizootic in broodstock “coaster” brook trout (Salvelinus fontinalis) at the Iron River National Fish Hatchery. The epizootic spanned more than a year, was unresponsive to multiple florfenicol treatments, and resulted in >50% mortality of the affected fish. The decision was made to cull the remaining fish during spawning, which presented an opportunity to more thoroughly examine V. salmoninarum sampling methods, organ tropism and vertical transmission. A newly developed qPCR targeting the pheS gene was used in concert with bacterial culture to show that V. salmoninarum indeed disproportionately affects females and has a tropism for female reproductive tissues. The study demonstrates that some female reproductive tissues (e.g. ovarian fluid, unfertilized eggs) are also an effective option for non-lethal detection. Despite the widespread presence of V. salmoninarum in ovarian fluid and on egg surfaces, we found no evidence of intra-ova transmission.     

Genome-wide association analysis of resistance to Pythium ultimum in common bean (Phaseolus vulgaris)

Pythium root rot (PRR) caused by Pythium spp. is an important root rot disease affecting common bean productivity. The objective of this study was to conduct a genome-wide association analysis of resistance to PRR in the common bean of Andean gene pool using single nucleotide polymorphism (SNP) markers. About 260 genotypes of the Andean diversity panel (ADP) were evaluated under screen house conditions using Pythium ultimum isolate MS61 in Uganda. Sixteen significant signals for resistance to PRR were detected on chromosomes Pv01, Pv02, Pv04, Pv05 and Pv09 using 260K GBS-based and 6K Beadchip SNPs. Common significant signals were detected on Pv02 and Pv09 for PRR. Positional candidate genes associated with significant SNPs on Pv02 were Phvul.002G119700, 16.97 kb near marker S02_25507837 (25.50 Mb), encoding Subtilase family protein, and Phvul.002G278400 near marker ss715645959 (44.79 Mb) encoding Defensin-like (DEFL) protein involved in plant defence responses. Based on the relatively high heritability estimates observed for PRR in this study, significant SNP markers associated with genomic regions for resistance to PRR could be validated for marker-assisted breeding in Andean beans.     

Pyrethroid synergism by esterase inhibition in Spodoptera littoralis (Boisduval) larvae

The susceptibility of cotton leafworm, Spodoptera littoralis (Boisduval) larvae to poisoning by trans-permethrin and cis-cypermethrin was increased when these pyrethroids were applied topically after the larvae had ingested profenofos, monocrotophos or azinphos-methyl for 24 h. An ingested dose of 4 nmol profenofos per larva gave a synergism factor of about threefold for both trans-permethrin and cis-cypermethrin. These pyrethroids were not synergized by oxidase inhibitors such as piperonyl butoxide, SV-1 and MPP ingested at 80 nmol/larva. Esterase preparations of larval gut hydrolysed trans-permethrin two to three times more rapidly than cis-permethrin, deltamethrin, trans- or cis-cypermethrin. Integument esterase(s) are less active but show a similar preference for trans-permethrin. The gut esterase(s) hydrolysing trans-permethrin are more sensitive in vitro and in vivo to inhibition by profenofos than by azinphos-methyl or monocrotophos. The susceptibility of S. littoralis larvae to pyrethroids appears to be limited by pyrethroid esterases in the gut. Organophosphorous compounds inhibiting these detoxifying enzymes serve as synergists.     

BRCT repeats as phosphopeptide-binding modules involved in protein targeting

We used a proteomic approach to identify phosphopeptide-binding modules mediating signal transduction events in the DNA damage response pathway. Using a library of partially degenerate phosphopeptides, we identified tandem BRCT (BRCA1 carboxyl-terminal) domains in PTIP (Pax transactivation domain-interacting protein) and in BRCA1 as phosphoserine- or phosphothreonine-specific binding modules that recognize substrates phosphorylated by the kinases ATM (ataxia telangiectasia-mutated) and ATR (ataxia telangiectasia- and RAD3-related) in response to gamma-irradiation. PTIP tandem BRCT domains are responsible for phosphorylation-dependent protein localization into 53BP1- and phospho-H2AX (gamma-H2AX)-containing nuclear foci, a marker of DNA damage. These findings provide a molecular basis for BRCT domain function in the DNA damage response and may help to explain why the BRCA1 BRCT domain mutation Met1775 --> Arg, which fails to bind phosphopeptides, predisposes women to breast and ovarian cancer.     

Archeological traces of early hominid activities, East of lake Rudolf, kenya

Excavations have demonstrated that stone artifacts occur stratified within beds of Lower Pleistocene (or end Pliocene) age. At one site a low-density scatter of worked stone objects occurs together with small but significant quantities of broken-up bones. Potassium-argon dates indicate an age greater than 2 million years; thus, this may be the oldest known hominid occupation site. More than 20 hominid fossils have been recovered from various sedimentary formations in the area.     

Impacts of fishing low-trophic level species on marine ecosystems

Low-trophic level species account for more than 30% of global fisheries production and contribute substantially to global food security. We used a range of ecosystem models to explore the effects of fishing low-trophic level species on marine ecosystems, including marine mammals and seabirds, and on other commercially important species. In five well-studied ecosystems, we found that fishing these species at conventional maximum sustainable yield (MSY) levels can have large impacts on other parts of the ecosystem, particularly when they constitute a high proportion of the biomass in the ecosystem or are highly connected in the food web. Halving exploitation rates would result in much lower impacts on marine ecosystems while still achieving 80% of MSY.