Could the egg itself be the source of the oviposition deterrent marker in the ectoparasitoid Dinarmus basalis?

Females of Dinarmus basalis, a solitary ectoparasitoid, strongly avoid superparasitising hosts bearing eggs which are 20 or more hours old. Our objective was to determine the mechanism by which the factors inducing host discrimination and such an oviposition deterring effect act, and the origin of the deterrent. This study showed that the information is carried by the parasitised host. It is acquired by a transfer of molecules from the wasp egg onto the host and it requires contact between egg and host for at least 4 h. The factors transferred do not, as commonly reported in other species, come from the female's genital apparatus but from the live egg itself. Consequently, the D. basalis egg directly participates in the success of parasitism by releasing factors which elicit the oviposition host deterring effect. The originality and the ecological importance of these results are discussed.     

Prevalence and seasonal variations of six bee viruses in Apis mellifera L. and Varroa destructor mite populations in France

A survey of six bee viruses on a large geographic scale was undertaken by using seemingly healthy bee colonies and the PCR technique. Samples of adult bees and pupae were collected from 36 apiaries in the spring, summer, and autumn during 2002. Varroa destructor samples were collected at the end of summer following acaricide treatment. In adult bees, during the year deformed wing virus (DWV) was found at least once in 97% of the apiaries, sacbrood virus (SBV) was found in 86% of the apiaries, chronic bee paralysis virus (CBPV) was found in 28% of the apiaries, acute bee paralysis virus (ABPV) was found in 58% of the apiaries, black queen cell virus (BQCV) was found in 86% of the apiaries, and Kashmir bee virus (KBV) was found in 17% of the apiaries. For pupae, the following frequencies were obtained: DWV, 94% of the apiaries; SBV, 80% of the apiaries; CBPV, none of the apiaries; ABPV, 23% of the apiaries; BQCV, 23% of the apiaries; and KBV, 6% of the apiaries. In Varroa samples, the following four viruses were identified: DWV (100% of the apiaries), SBV (45% of the apiaries), ABPV (36% of the apiaries), and KBV (5% of the apiaries). The latter findings support the putative role of mites in transmitting these viruses. Taken together, these data indicate that bee virus infections occur persistently in bee populations despite the lack of clinical signs, suggesting that colony disease outbreaks might result from environmental factors that lead to activation of viral replication in bees.     

Purification, cloning, and sequencing of a 3,5-dichlorophenol reductive dehalogenase from Desulfitobacterium frappieri PCP-1

A membrane-associated 3,5-dichlorophenol reductive dehalogenase was isolated from Desulfitobacterium frappieri PCP-1. The highest dehalogenase activity was observed with the biomass cultured at 22 degrees C, compared to 30 and 37 degrees C, where the cell suspensions were 2.2 and 9.6 times less active, respectively. The reductive dehalogenase was purified 12.7-fold to apparent homogeneity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed a single band with an apparent molecular mass of 57 kDa. Its dechlorinating activity was not inhibited by sulfate and nitrate but was completely inhibited by 2.5 mM sulfite and 10 mM KCN. A mixture of iodopropane and titanium citrate caused a light-reversible inhibition of the dechlorinating activities, suggesting the involvement of a corrinoid cofactor. Several polychlorophenols were dechlorinated at the meta and para positions. The apparent K(m) for 3,5-dicholorophenol was 49.3 +/- 3.1 microM at a methyl viologen concentration of 2 mM. Six internal tryptic peptides were sequenced by mass spectrometry. One open reading frame (ORF) was found in the Desulfitobacterium hafniense genome containing these peptide sequences. This ORF corresponds to a gene coding for a CprA-type reductive dehalogenase. The corresponding ORF (named cprA5) in D. frappieri PCP-1 was cloned and sequenced. The cprA5 gene codes for a 548-amino-acid protein that contains a twin-arginine-type signal for secretion. The gene product has a cobalamin binding site motif and two iron-sulfur binding motifs and shows 66% identity (76 to 77% similarity) with some tetrachloroethene reductive dehalogenases. This is the first CprA-type reductive dehalogenase that can dechlorinate chlorophenols at the meta and para positions.     

Trophic interactions in a high arctic snow goose colony

We examined the role of trophic interactions in structuringa high arctic tundra community characterized by a large breedingcolony of greater snow geese (Chen caerulescens atlantica).According to the exploitation ecosystem hypothesis of Oksanenet al. (1981), food chains are controlled by top-down interactions.However, because the arctic primary productivity is low, herbivorepopulations are too small to support functional predator populationsand these communities should thus be dominated by the plant/herbivore trophic-level interaction. Since 1990, we have beenmonitoring annual abundance and productivity of geese, the impactof goose grazing, predator abundance (mostly arctic foxes, Alopexlagopus) and the abundance of lemmings, the other significantherbivore in this community, on Bylot Island, Nunavut, Canada.Goose grazing consistently removed a significant proportionof the standing crop (     

Annotated expressed sequence tags for studies of the regulation of reproductive modes in aphids

The damaging effect of aphids to crops is largely determined by the spectacular rate of increase of populational expansion due to their parthenogenetic generations. Despite this, the molecular processes triggering the transition between the parthenogenetic and sexual phases between their annual life cycle have received little attention. Here, we describe a collection of genes from the cereal aphid Rhopalosiphum padi expressed during the switch from parthenogenetic to sexual reproduction. After cDNA cloning and sequencing, 726 expressed sequence tags (EST) were annotated. The R. padi EST collection contained a substantial number (139) of bacterial endosymbiont sequences. The majority of R. padi cDNAs encoded either unknown proteins (56%) or housekeeping polypeptides (38%). The large proportion of sequences without similarities in the databases is related to both their small size and their high GC content, corresponding probably to the presence of 5'-unstranslated regions. Fifteen genes involved in developmental and differentiation events were identified by similarity to known genes. Some of these may be useful candidates for markers of the early steps of sexual differentiation.     

Palaeoecology of triassic stem turtles sheds new light on turtle origins

Competing hypotheses of early turtle evolution contrast sharply in implying very different ecological settings-aquatic versus terrestrial-for the origin of turtles. We investigate the palaeoecology of extinct turtles by first demonstrating that the forelimbs of extant turtles faithfully reflect habitat preferences, with short-handed turtles being terrestrial and long-handed turtles being aquatic. We apply this metric to the two successive outgroups to all living turtles with forelimbs preserved, Proganochelys quenstedti and Palaeochersis talampayensis, to discover that these earliest turtle outgroups were decidedly terrestrial. We then plot the observed distribution of aquatic versus terrestrial habits among living turtles onto their hypothesized phylogenies. Both lines of evidence indicate that although the common ancestor of all living turtles was aquatic, the earliest turtles clearly lived in a terrestrial environment. Additional anatomical and sedimentological evidence favours these conclusions. The freshwater aquatic habitat preference so characteristic of living turtles cannot, consequently, be taken as positive evidence for an aquatic origin of turtles, but must rather be considered a convergence relative to other aquatic amniotes, including the marine sauropterygians to which turtles have sometimes been allied.     

A revised annotation and comparative analysis of Helicobacter pylori genomes

Huge amounts of genomic information are currently being generated. Therefore, biologists require structured, exhaustive and comparative databases. The PyloriGene database (http://genolist.pasteur.fr/PyloriGene) was developed to respond to these needs, by integrating and connecting the information generated during the sequencing of two distinct strains of Helicobacter pylori. This led to the need for a general annotation consensus, as the physical and functional annotations of the two strains differed significantly in some cases. A revised functional classification system was created to accommodate the existing data and to make it possible to classify coding sequences (CDS) into several functional categories to harmonize CDS classification. The annotation of the two complete genomes was revised in the light of new data, allowing us to reduce the percentage of hypothetical proteins from approximately 40 to 33%. This resulted in the reassignment of functions for 108 CDS (approximately 7% of all CDS). Interestingly, the functions of only approximately 13% of CDS (222 out of 1658 CDS) were annotated as a result of work done directly on H.pylori genes. Finally, comparison of the two published genomes revealed a significant amount of size variation between corresponding (orthologous) CDS. Most of these size variations were due to natural polymorphisms, although other sources of variation were identified, such as pseudogenes, new genes potentially regulated by slipped-strand mispairing mechanism, or frame-shifts. 113 of these differences were due to different start codon assignments, a common problem when constructing physical annotations.     

Comparison of vasodilatory properties of 14,15-EET analogs: structural requirements for dilation

Epoxyeicosatrienoic acids (EETs) are endothelium-derived eicosanoids that activate potassium channels, hyperpolarize the membrane, and cause relaxation. We tested 19 analogs of 14,15-EET on vascular tone to determine the structural features required for activity. 14,15-EET relaxed bovine coronary arterial rings in a concentration-related manner (ED(50) = 10(-6) M). Changing the carboxyl to an alcohol eliminated dilator activity, whereas 14,15-EET-methyl ester and 14,15-EET-methylsulfonimide retained full activity. Shortening the distance between the carboxyl and epoxy groups reduced the agonist potency and activity. Removal of all three double bonds decreased potency. An analog with a Delta8 double bond had full activity and potency. However, the analogs with only a Delta5 or Delta11 double bond had reduced potency. Conversion of the epoxy oxygen to a sulfur or nitrogen resulted in loss of activity. 14(S),15(R)-EET was more potent than 14(R),15(S)-EET, and 14,15-(cis)-EET was more potent than 14,15-(trans)-EET. These studies indicate that the structural features of 14,15-EET required for relaxation of the bovine coronary artery include a carbon-1 acidic group, a Delta8 double bond, and a 14(S),15(R)-(cis)-epoxy group.