Random Amplified Polymorphic DNA Variation among and within Selected Ixora (Rubiaceae) Populations and Mutants

Random amplified polymorphic DNA (RAPD) analysis was used tostudy variation among and within selectedIxora (Rubiaceae) populationsand mutants. Six populations of I. congesta yielded identicalbanding patterns suggesting genetic uniformity of this species.However, six populations of I. coccinea varieties (three red-flowered,two yellow-flowered and one red-flowered wild-type) exhibitedinfraspecific differences in RAPD profiles. Small and largeleaves of an atavistic mutant cultivar of I. coccinea were alsosubjected to RAPD analysis. An extra band was amplified in thelarge leaves that was absent in small leaves, suggesting thatthe phenotypic alteration in this taxon is due to genetic mutationrather than epigenetic changes. Similarly, an extra band wasdetected in the white sectors of I. Variegated compared to thegreen sectors, suggesting that the shoot apical meristems ofthis cultivar exist as a genetic chimera. DNA gel blot hybridizationwas performed to confirm the specificities of selected bands.Our study indicates that differences among individuals of variouspopulations and mutants may be detected using RAPD markers.Copyright 1999 Annals of Botany Company Ixora L., variegated variety, RAPD fingerprinting, DNA gel blot, intraspecific genetic similarity, atavistic mutant.     

Sows affect their piglets’ faecal microbiota until fattening but not their Salmonella enterica shedding status

Recent studies have shown that Salmonella shedding status affects sows’ microbiota during gestation and that these modifications are reflected in the faecal microbiota of their piglets at weaning. The aims of this study were: (a) to evaluate the persistence, up to the fattening period, of the previously measured link between the microbiota of piglets and their mothers’ Salmonella shedding status; and (b) measure the impact of the measured microbiota variations on their Salmonella excretion at this stage. To achieve this, 76 piglets born from 19 sows for which the faecal microbiota was previously documented, were selected in a multisite production system. The faecal matter of these swine was sampled after 4 weeks, at the fattening stage. The Salmonella shedding status and faecal microbiota of these animals were described using bacteriological and 16S rRNA gene amplicon sequencing respectively. The piglet digestive microbiota association with the Salmonella shedding status of their sows did not persist after weaning and did not affect the risk of Salmonella excretion during fattening, while the birth mother still affected the microbiota of the swine at fattening. This supports the interest in sows as a target for potentially transferrable microbiota modifications.     

Ecological interactions in Aedes species on Reunion Island

Two invasive, container‐breeding mosquito species, Aedes aegypti (Stegomyia aegypti) and Aedes albopictus (Stegomyia albopicta) (Diptera: Culicidae), have different distribution patterns on Reunion Island. Aedes albopictus occurs in all areas and Ae. aegypti colonizes only some restricted areas already occupied by Ae. albopictus. This study investigates the abiotic and biotic ecological mechanisms that determine the distribution of Aedes species on Reunion Island. Life history traits (duration of immature stages, survivorship, fecundity, estimated finite rate of increase) in Ae. aegypti and Ae. albopictus were compared at different temperatures. These fitness measures were characterized in both species in response to competitive interactions among larvae. Aedes aegypti was drastically affected by temperature, performing well only at around 25 °C, at which it achieved its highest survivorship and greatest estimated rate of increase. The narrow distribution of this species in the field on Reunion Island may thus relate to its poor ability to cope with unfavourable temperatures. Aedes aegypti was also more negatively affected by high population densities and to some extent by interactions with Ae. albopictus, particularly in the context of limited food supplies. Aedes albopictus exhibited better population performance across a range of environmental conditions. Its ecological plasticity and its superior competitive ability relative to its congener may further enhance its invasion success on Reunion Island.     

Crystal structure of a novel mid-gut procarboxypeptidase from the cotton pest Helicoverpa armigera.

The cotton bollworm Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) is one of the most serious insect pests in Australia, India and China. The larva causes substantial economical losses to legume, fibre, cereal oilseed and vegetable crops. This pest has proven to be difficult to control by conventional means, mainly due to the development of pesticide resistance. We present here the 2.5 A crystal structure from the novel procarboxypeptidase (PCPAHa) found in the gut extracts from H. armigera larvae, the first one reported for an insect. This metalloprotease is synthesized as a zymogen of 46.6 kDa which, upon in vitro activation with Lys-C endoproteinase, yields a pro-segment of 91 residues and an active carboxypeptidase moiety of 318 residues. Both regions show a three-dimensional structure quite similar to the corresponding structures in mammalian digestive carboxypeptidases, the most relevant structural differences being located in the loops between conserved secondary structure elements, including the primary activation site. This activation site contains the motif (Ala)(5)Lys at the C terminus of the helix connecting the pro- and the carboxypeptidase domains. A remarkable feature of PCPAHa is the occurrence of the same (Ala)(6)Lys near the C terminus of the active enzyme. The presence of Ser255 in PCPAHa instead of Ile and Asp found in the pancreatic A and B forms, respectively, enlarges the S1' specificity pocket and influences the substrate preferences of the enzyme. The C-terminal tail of the leech carboxypeptidase inhibitor has been modelled into the PCPAHa active site to explore the substrate preferences and the enzymatic mechanism of this enzyme.     

Immunologic and nonimmunologic responsiveness in ragweed-sensitized dogs

The relationship between airway responsiveness to inhaled antigen and histamine, immunologic release of lung histamine, immunologic responsiveness of skin, and specific immunoglobulin E (IgE) antibodies were examined in 11 inbred allergic dogs immunized with extracts of ragweed and grass and 5 nonimmunized control dogs from the same colony. Airway responsiveness to antigen and histamine was characterized by the doses that increased the airflow resistance of the total respiratory system to twice the control values (ED200). Highly significant correlations were found between airway responsiveness and cutaneous responsiveness to antigen and other immunologic characteristics (e.g., IgE and histamine released from lung by inhaled antigen) in all dogs. In ragweed-sensitized dogs, there was an inverse correlation between immunologic responsiveness (reflected by the cutaneous response to antigen and histamine released from lung by inhaled antigen) and nonimmunologic responsiveness of airways (histamine ED200: r = 0.73, P less than 0.05 and r = 0.75, P less than 0.01, respectively). Antigen ED200 was also correlated with histamine release from lung after antigen inhalation (r = 0.74; P less than 0.01). We conclude that airway reactions to inhaled antigen in allergic dogs are dependent not only on immunologic factors but also on the degree of nonimmunologic airway responsiveness to histamine and that these factors are correlated inversely.