Molecular heterosis at the conalbumin locus in the ring-necked pheasant (Phasianus colchicus)

Summary Egg whites of Phasianus colchicus containing conalbumin of the heterozygous type show a stronger inhibitory effect on the growth of Saccharomyces cerevisiae than egg whites with conalbumin of the common homozygous type. This fact is interpreted as an example of heterosis at the molecular level.     

Involvement of fixLJ in the regulation of nitrogen fixation in Azorhizobium caulinodans

A gene bank of Azorhizobium caulinodans DNA constructed in the bacteriophage lambda GEM11 was screened with Rhizobium meliloti fixL and fixJ genes as probes. One positive recombinant phage, ORS lambda L, was isolated. The nucleotide sequence of a 3.7 kb fragment was established. Two open reading frames of 1512bp and 613bp were identified as fixL and fixJ. Kanamycin cartridges were inserted into the cloned fixL and fixJ genes and recombined into the host genome. The resulting mutants were Nif- Fix-, suggesting that the two genes were required for symbiotic nitrogen fixation and for nitrogen fixation in the free-living state. Using pnifH-lacZ and pnifA-lacZ fusions, it was shown that the FixLJ products controlled the expression of nifH and nifA in bacteria grown in the free-living state.     

Chemical convergence between a guild of facultative myrmecophilous caterpillars and host plants

1. Ants exert strong selective pressure on herbivorous insects, although some caterpillars can live in symbiosis with them using chemical defensive strategies.
2. We investigated the adaptive resemblance of cuticular hydrocarbons (CHCs) in multitrophic systems involving a guild of facultative myrmecophilous caterpillar species (Lepidoptera: Lycaenidae), tending ants (Hymenoptera: Formicidae), and host plants from three families. We hypothesised that the CHCs of the caterpillars would resemble those of their host plants (chemical camouflage).
3. We analysed CHCs using gas chromatography/mass spectrometry. Morisita's similarity index (SI) was used to compare CHC profiles of caterpillar species with different types of ant associations (commensal or mutualistic), ants, and host plants.
4. We found strong convergence between caterpillars' CHCs and plants, especially for commensal species that do not provide secretion rewards for ants. Moreover, we found unexpected chemical convergence among mutualistic (trophobiotic) caterpillar species that offer caloric reward secretions to ants.
5. These results show that the studied caterpillars acquire CHCs through their diet and that they vary according to host plant species and type of ant association (commensalism or mutualism). This ‘chemical camouflage’ of myrmecophilous caterpillars may have arisen as a defensive strategy allowing coexistence with ants on plants, whereas ‘chemical conspicuousness’ may have evolved in the context of honest signalling between mutualistic partners.
6. We suggest the existence of chemical mimicry among myrmecophilous species, especially between mutualistic caterpillars. Cuticular chemical mixtures can play a key adaptive role in decreasing ant attacks and increasing caterpillar survival in multimodal sensory systems.

     

Characterisation of the glnK-amtB operon and the involvement of AmtB in methylammonium uptake in Azorhizobium caulinodans

This work reports the characterisation of the Azorhizobium caulinodans amtB gene, the deduced protein sequence of which shares similarity to those of several ammonium transporters. amtB is located downstream from glnK, a glnB-like gene. It is cotranscribed with glnK from an NtrC- and σ⁵⁴-dependent promoter. glnK and amtB insertion mutant strains have been isolated. Methylammonium uptake was assayed in these strains and in other mutant strains in which the regulation of nitrogen metabolism is impaired. Our data suggest that the AmtB protein is an ammonium transporter, which is mainly regulated by NtrC in response to nitrogen availability.     

Plant–treehopper convergence may trick butterflies into trophic oviposition mistakes

Our research aimed to compare the chemical cues of treehoppers and host plants in two rare cases of herbivorous myrmecophilous butterflies laying eggs on treehoppers. Our hypothesis that the cuticular hydrocarbon (CHC) profiles of the treehoppers would resemble those of their host plants was confirmed.     

In vitro Inoculation Studies for Estimating the Susceptibility of Ornamental Plants to Phytophthora ramorum

Susceptibility evaluation of plant species towards Phytophthora ramorum is essential for pest risk assessment of the pathogen in Europe. An in vitro inoculation method on detached leaves and twigs was used to estimate the susceptibility of some leading ornamental plant species in Germany. Ratings in susceptibility of plant species and cultivars were classified according to the degree of symptoms caused by P. ramorum . Buxus sp., Hedera helix , Vaccinium corymbosum and V. macrocarpon were classified as not susceptible whereas most Calluna vulgaris cultivars, Erica carnea 'Schneekuppe', E. gracilis , Vaccinium myrtillus and Vaccinium oxycoccus ranged in the 'highly susceptible' category. Erica carnea 'Rubinfeuer ' and E. cinerea were classified as moderately susceptible whereas E. x darleyensis and Rhododendron simsii were classified as slightly susceptible. Different susceptibility reactions between cultivars were only found for R. simsii and C. vulgaris . Symptom development was effected by wounding only for R. simsii , V. corymbosum and V. oxycoccus .