Larval feeding behaviour of Tetanocera elata (Diptera: Sciomyzidae): potential biocontrol agent of pestiferous slugs

Examining predatory behaviour is useful for determining the potential of novel biocontrol agents. We investigated the predatory behaviour of Tetanocera elata (Fabricius) larvae on the pestiferous slug Deroceras reticulatum (Müller). Results indicate three prey-finding strategies, including the predator reaching its prey without previous contact with it or its mucus trail.     

Veterinary trypanocidal benzoxaboroles are peptidase-activated prodrugs

Livestock diseases caused by Trypanosoma congolense, T. vivax and T. brucei, collectively known as nagana, are responsible for billions of dollars in lost food production annually. There is an urgent need for novel therapeutics. Encouragingly, promising antitrypanosomal benzoxaboroles are under veterinary development. Here, we show that the most efficacious subclass of these compounds are prodrugs activated by trypanosome serine carboxypeptidases (CBPs). Drug-resistance to a development candidate, AN11736, emerged readily in T. brucei, due to partial deletion within the locus containing three tandem copies of the CBP genes. T. congolense parasites, which possess a larger array of related CBPs, also developed resistance to AN11736 through deletion within the locus. A genome-scale screen in T. brucei confirmed CBP loss-of-function as the primary mechanism of resistance and CRISPR-Cas9 editing proved that partial deletion within the locus was sufficient to confer resistance. CBP re-expression in either T. brucei or T. congolense AN11736-resistant lines restored drug-susceptibility. CBPs act by cleaving the benzoxaborole AN11736 to a carboxylic acid derivative, revealing a prodrug activation mechanism. Loss of CBP activity results in massive reduction in net uptake of AN11736, indicating that entry is facilitated by the concentration gradient created by prodrug metabolism.     

Emergence and dispersal relative to natal nest in the digger wasp Stizus continuus (Hymenoptera: Crabronidae)

The position of the emerging point has rarely been investigated as a factor possibly affecting the future nest settlement behaviour in Hymenoptera, in particular within nest aggregations. We studied the emergence and dispersion patterns of the digger wasp Stizus continuus. Individuals emerged daily in clumped patterns, possibly revealing a certain synchrony of emergence from the same nests, and protandry appeared both at seasonal and daily level. Differences between the number of females that nested relatively close or far from their emergence holes (EH) were either significant or not, depending on the year, and observed dispersal distances from the natal nests did not differ from those obtained by random simulations. By contrast, females nested close to the nearest conspecific nest. Size did not affect the dispersion patterns. EH are thus not important cues for nest establishment, and conspecific nests are probably the key cue for nest-founding females. In addition, males did not prefer to establish territories close to their natal nest.     

Influence of oxygen on the microsomal electron transport system in Saccharomyces cerevisiae

The influence of oxygen on the level of microsomal electron transport chain components has been studied during the growth of Saccharomyces cerevisiae. Enzyme activities and cytochrome content were assayed in microsomal fractions prepared from a protoplast lysate free from mitochondrial contamination. It was found that the cytochrome P-450 and cytochrome b5 content, to get her with the NADPH-cytochrome (P-450)-reductase and NADH-cytochrome (b5)-reductase activities, were increased in the cells as the pO2 of the medium was decreasing. At the same time an increase in the membrane surface of the endoplasmic reticulum can be observed.     

Identification by suppression subtractive hybridization of genes expressed in pear (Pyrus spp.) upon infestation with Cacopsylla pyri (Homoptera: Psyllidae)

The molecular interaction between pear tree (Pyrus spp.) and the phloem-feeding psylla Cacopsylla pyri (Linnaeus) was investigated through the construction and characterization of cDNA subtracted libraries. Genes expressed upon insect infestation were identified in the susceptible pear cultivar Bartlett and in the resistant selection NY10355. In both interactions, genes involved in the plant defense response were induced, confirming the observed similarity between the response to pathogens and to insects with piercing/sucking mouthparts. However, the two expression profiles were found to be different, with more genes involved in the response to biotic and abiotic stress being activated in the resistant plant than in the susceptible one. Further characterization of the identified genes could lead to the development of molecular markers associated with tolerance/resistance to pear psylla.     

Heterochromatin and repetitive DNA frequency variation in regenerated plants of Helianthus annuus L.

Plant regeneration from cotyledons of seeds of a single progeny of a pure line of Helianthus annuus was studied in respect of the nuclear DNA contents of control and regenerated plants. Control plants were divided into two groups: those developed from seeds at the periphery of the inflorescence (showing a high basic 4C DNA content) and those from seeds developed in the middle of the inflorescence (showing a low basic 4C DNA content). It was observed that plants from peripheral seeds have a higher morphogenetic potential than those from central seeds. Cytophotometric analyses indicated that plants regenerated from cotyledons of both peripheral and central seeds show the same basic 4C DNA amount, which is higher that that observed in vivo in peripheral seeds. Molecular analysis by slot blotting and hybridization with different DNA families showed that the difference in nuclear DNA content between plants from peripheral and central seeds in vivo are mainly related to differences in the frequency of highly repeated, slow medium repeated (MR2), and ribosomal DNA families; by contrast, the increase in DNA amount in regenerated plants is mainly due to fast medium repeated sequences (MR1). Moreover, the frequency of kinetically isolated unique sequences was higher in peripheral seeds than in central ones and still higher in regenerated plants. Optical-density measurements of interphase nuclei showed an increase of heterochromatin in regenerated plants, suggesting that, whatever DNA is amplified in these plants, it remains condensed and probably inactive.Research supported by National Research Council of Italy, Special Project RAISA, Sub-project No. 2, Paper No. 2069     

PrPSc in salivary glands of scrapie-affected sheep

The salivary glands of scrapie-affected sheep and healthy controls were investigated for the presence of the pathological prion protein (PrP(Sc)). PrP(Sc) was detected in major (parotid and mandibular) and minor (buccal, labial, and palatine) salivary glands of naturally and experimentally infected sheep. Using Western blotting, the PrP(Sc) concentration in glands was estimated to be 0.02 to 0.005% of that in brain. Immunohistochemistry revealed intracellular depositions of PrP(Sc) in ductal and acinar epithelia and occasional labeling in the lumina of salivary ducts. The presence of PrP(Sc) in salivary glands highlights the possible role of saliva in the horizontal transmission of scrapie.