Transposition-mediated transcriptional overexpression as a mechanism of insecticide resistance

It has been proposed that amplification of genes for esterase that provide resistance to insecticides may originate from transposition events. To test this hypothesis, we have constructed a minigene coding for a soluble acetylcholinesterase under the control of a nontissue-specific promoter (hsp70). When introduced into Drosophila, the gene is expressed in all tissues and the extra acetylcholinesterase produced confers a low level of insecticide resistance (twofold). The minigene was mobilized by crossing the initial transformant with a strain providing a source of P-element transposase. After 34 generations of exposure to the organophosphate parathion, we obtained a strain with a higher resistance (fivefold). This strain had only one extra Ace gene, which overexpressed acetylcholinesterase. Thus, following transposition, resistance resulted from the overexpression of a single copy of the gene and not from gene amplification. Received: 9 August 1996 / Accepted: 27 May 1997     

UDP-N-acetylglucosamine 1-carboxyvinyl-transferase from Acinetobacter calcoaceticus

Abstract We have analyzed the sequence downstream of rpoN from Zcinetobacter calcoaceticus and identified an open reading frame encoding a protein with high similarity to UDP- N -acetylgucosamine 1-carboxyvinyl-transferase (MurZ). Multicopy plasmids encoding this enzyme conferred phosphomycin resistance to A. calcoaceticus . The polar effect of a rpoN mutation on the phosphomycin resistance level suggests that murZ is, in part, cotranscribed with rpoN . These observations confirm that A. calcoaceticus represents the first exceptin from a conserved genetic context of rpoN observed in several other Gram-negative bacteria.     

Cloning of aroG, the gene coding for phospho-2-keto-3-deoxy-heptonate aldolase(phe), in Escherichia coli K-12, and subcloning of the aroG promoter and operator in a promoter-detecting plasmid

Defective transducing phages carrying aroG, the structural gene for phenylalanine (phe)-inhibitable phospho-2-keto-heptonate aldolase (EC 4.1.2.15; previously known as 3-deoxy-D-arabinoheptulosonate-7-phosphate synthetase[phe]), have been isolated, and DNA from two of these phages has been used to construct a restriction map of the region from att lambda to aroG. A 7.6-kb PstI-HindIII fragment from one of these phages was cloned into pBR322 and shown to contain aroG. The location of aroG within the 7.6 kb was established by subcloning and Tn3 transpositional mutagenesis. A fragment carrying the aroG promoter and operator has been cloned into a high copy number promoter-cloning vector (pMC489), and the resulting aroGpo-LacZ' (alpha) fusion subcloned in a low copy number vector. Strains with this fusion on the low copy number vector exhibit negative regulation of beta-galactosidase expression by both phenylalanine and tryptophan and positive regulation by tyrosine in a tyrR+ background.     

Modelling multilocus selection in an individual‐based,spatially‐explicit landscape genetics framework

We implemented multilocus selection in a spatially‐explicit, individual‐based framework that enables multivariate environmental gradients to drive selection in many loci as a new module for the landscape genetics programs, CDPOP and CDMetaPOP. Our module simulates multilocus selection using a linear additive model, providing a flexible platform to evaluate a wide range of genotype‐environment associations. Importantly, the module allows simulation of selection in any number of loci under the influence of any number of environmental variables. We validated the module with individual‐based selection simulations under Wright‐Fisher assumptions. We then evaluated results for simulations under a simple landscape selection model. Next, we simulated individual‐based multilocus selection across a complex selection landscape with three loci linked to three different environmental variables. Finally, we demonstrated how the program can be used to simulate multilocus selection under varying selection strengths across different levels of gene flow in a landscape genetics framework. This new module provides a valuable addition to the study of landscape genetics, allowing for explicit evaluation of the contributions and interactions between gene flow and selection‐driven processes across complex, multivariate environmental and landscape conditions.     

Taste receptor activity and feeding behaviour reveal mechanisms of white spruce natural resistance to Eastern spruce budworm Choristoneura fumiferana

The pattern of feeding of Eastern spruce budworm Choristoneura fumiferana (Clem.) (Lepidoptera, Tortricidae) is compared on foliage from white spruce Picea glauca (Moench) Voss. (Pinaceae) trees previously determined to be susceptible and resistant to defoliation by budworm. No differences are observed in electrophysiological responses from taste sensilla to aqueous extracts of the two foliage types, nor is there a preference for either extract type in a choice test. Acetone extracts from the two foliage types are both preferred to a control sucrose solution, although neither elicits a preference relative to the other. These results suggest that there is no difference in phagostimulatory power of internal leaf contents of the two foliage types. Longer‐term observation of feeding behaviour in a no‐choice situation shows no difference in meal duration, confirming the lack of difference in phagostimulatory power. However, on average, intermeal intervals are twice as long on the resistant foliage, leading to an overall lower food consumption during the assay. This result suggests an anti‐digestive or toxic effect of the resistant foliage that slows behaviour and limits food intake. Previous research has shown that waxes of the resistant foliage deter initiation of feeding by the spruce budworm and that this foliage contains higher levels of tannins and monoterpenes. The data suggest that the resistant foliage contains a post‐ingestive second line of defence against the spruce budworm.     

Hepatic DNAJB9 Drives Anabolic Biasing to Reduce Steatosis and Obesity

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Population Dynamics,Root Penetration,and Feeding Behavior of Pratylenchus agilis in Monoxenic Root Cultures of Corn,Tomato, and Soybean

Population dynamics, rate of root penetration, and external root feeding behavior of Pratylenchus agilis (Pa) in monoxenic cultures of intact corn seedlings and root explants of corn, tomato, and soybean were studied. In descending order of suitability as hosts were I. O. Chief corn, Rutgers tomato, and Williams soybean. Soybean entries Kent, Pickett 71, PI 90763, and Essex were poor hosts. Numbers of eggs and vermiform Pa in the agar medium indicated total fecundity and host suitability. Agar, sand, or soil as support media did not appear to affect Pa root penetration, but the rate of corn root growth did. Whereas most vermiform Pa and eggs were in roots, substantial numbers appeared able to feed and complete their life cycle as ectoparasites on root epidermal cells and root hairs.