Flight Tunnel Responses of Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) to Olfactory and Visual Stimuli

Cohorts of mass-reared, naive Diachasmimorpha longicaudata, parasitoids of tephritid fruit flies, were released in a laminar airflow wind tunnel to study their responses to visual and olfactory stimuli associated with their host habitat. Parasitoids were five times more likely to land on yellow plastic spheres emitting the odor of ripe, guava fruit (Psidium guajava L.) than to spheres emitting clean air. The rate of landing was not modified by the presence of green artificial leaves adjacent to the spheres in the tunnel or by the inclusion of green leaf volatiles emanating with the guava odors. However, hovering activity was twice as frequent around spheres adjacent to artificial leaves than around isolated spheres. Oviposition activity on spheres emitting guava odor was not affected by the presence of artificial leaves nor by green leaf volatiles. This suggests that inexperienced D. longicaudata may be instinctively attracted to foliage and to fruit odor but that landing (arrestment) and oviposition are influenced more by odor than by the appearance of fruit or foliage. D. longicaudata are not instinctively attracted to larvae of Bactrocera dorsalis in the absence of host-habitat stimuli. More wasp activity occurred around oviposition units containing larvae if the odor of ripe/overripe guava was present. Successful wasp reproduction occurred only in units with guava odor.     

Probiotic Gut Microbiota Isolate Interacts with Dendritic Cells via Glycosylated Heterotrimeric Pili

Mapping of the microbial molecules underlying microbiota-host interactions is key to understand how microbiota preserve mucosal homeostasis. A pivotal family of such bacterial molecules are pili. Pili are proteinaceous cell wall appendages with a well-documented role in adhesion, whilst their role in immune interaction with the host is less established. Gram-positive pili are often posttranslationally modified by sortase-specific cleavage reactions and the formation of intramolecular peptide bonds. Here we report glycosylation as a new level of posttranslational modification of sortase-dependent pili of a beneficial microbiota species and its role in immune modulation. We focused on the SpaCBA pili of the model probiotic and beneficial human gut microbiota isolate Lactobacillus rhamnosus GG. A unique combination of molecular techniques, nanoscale mechanical and immunological approaches led to the identification of mannose and fucose residues on the SpaCBA pili. These glycans on the pili are recognized by human dendritic cells via the C-type lectin receptor DC-SIGN, a key carbohydrate-dependent immune tailoring pattern recognition receptor. This specific lectin-sugar interaction is moreover of functional importance and modulated the cytokine response of dendritic cells. This provides insight into the direct role bacterial glycoproteins can play in the immunomodulation of the host. Modification of the complex heterotrimeric pili of a model probiotic and microbiota isolate with mannose and fucose is of importance for the functional interaction with the host immune lectin receptor DC-SIGN on human dendritic cells. Our findings shed light on the yet underappreciated role of glycoconjugates in bacteria-host interactions.     

Effect of Diachasmimorpha tryoni on two non-target flowerhead-feedingtephritids

Laboratory tests were conducted to evaluate the possible effect of a deliberately introduced fruit fly parasitoid, Diachasmimorpha tryoni, on 2 non-target flowerhead-feeding tephritid flies,Trupanea dubautiae and Ensina sonchi. The former is an nativecomposite endemic Hawaiian tephritid which feeds on flowerheads of the native composite shrub, Dubautia raillar dioides; the latter is an inadvertently introduced tephritid infesting flowerheads of the exotic weed, Sonchus oleraceus. Gravid females of D. tryoniwere confined in test cages with field-collected D.raillardioides and S. oleraceus flowerheads infested with late instars of T. dubautiae and E. sonchi,respectively. D. tryoni showed low levels of visiting and probing responses to D. raillardioides flowerheads and relatively higher responses to S. oleraceus flower heads in both the presence and absence of the parasitoid's normal host, the Mediterranean fruit fly, Ceratitis capitata. With 72-h exposure to D. tryoni, 13.9 and 2.6% of T. dubautiaewere attacked by test parasitoids in the absence and presence of C.capitata in the test cage, respectively; while 56.8 and34.2% of E. sonchi were attacked. In contrast, 94.0 and84.0% of C. capitata larvae presented in screened disheswith diet in test cages were attacked by D. tryoni in testswith T. dubautiae and E. sonchi, respectively. Attackof D. tryoni on flowerhead-feeding T. dubautiae andE. sonchi resulted in significant reduction in the emergence ofadult flies, especially in the absence of the parasitoid's normal host.While 8.8–12.8 adult D. tryoni per test (both males andfemales) successfully emerged from medflies, no adult D. tryoniprogeny emerged from T. dubautiae, and only 3 deformed males ofD. tryoni (much smaller than the normal wasp) emerged fromE. sonchi. The relevance of these findings to the safety offuture biological control programs against tephritid pests is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Reversal of a trimethyltin-induced learning deficit by desglycinamide-8-arginine vasopressin

Trimethyltin (TMT) is an organometal neurotoxin which produces lesions primarily in the limbic system. Selectivity seems to depend upon the dose, but the hippocampus and related entorhinal cortical structures, of importance for learning and memory, are most often described as target sites. We have previously demonstrated that subjects treated with a moderate dose of TMT prior to acquisition sessions, are unable to learn a forward autoshaping task with a 6 sec delay of reinforcement, but are capable of acquiring the same task when no delay of reinforcement is used. These data suggested that the performance deficit is one of learning (i.e. consolidation) rather than of memory (i.e. storage), retrieval, or sensorimotor impairment. To more rigorously test this hypothesis, we determined if performance of a task already learned would be impaired by the neurotoxin. Adult male Long Evans rats were given 10 acquisition sessions of 24 trials, following which TMT (6.0 mg/kg, p.o.) was administered. One month later, these rats performed the lever-touching behavior as well as controls, despite the fact that the same dose of TMT interfered with learning if given one month prior to acquisition sessions, thus confirming our hypothesis. In a second experiment we determined if the peptide analog of vasopressin, desglycinamide-8-arginine vasopressin (DGAVP), could reverse a learning deficit in a population of non-learners. Rats were treated with TMT or water vehicle one month prior to autoshaping. TMT significantly retarded acquisition. After 10 sessions of 12 trials each, non-learners (i.e. rats treated with TMT that failed to associate the lever with delivery of a reinforcer) were administered saline or DGAVP (7.5 micrograms/kg, s.c.) 1 hr before sessions 11-13; treatment was discontinued prior to sessions 14 and 15. Peptide treated subjects showed evidence of acquisition and exhibited higher levels of lever-directed behavior than saline treated nonlearners. Performance was maintained after DGAVP treatment was discontinued, indicating that the learning-enhancing action of DGAVP was not transient or state-dependent.     

Amplicons of maize zein genes are conserved within genic but expanded and constricted in intergenic regions

The 78 101 base pair long sequence of a cluster of 22-kDa alpha zein genes in the maize inbred BSSS53 was determined. Each zein gene is contained within a repeat unit that varies in length. If such a repeat, or amplicon, is aligned along the entire sequence, a 10.5-fold sequence amplification is delineated. Because of insertions and deletions in intergenic regions, many of the zein genes are spaced over different distances. Only three out of 10 zein-related sequences have an intact open reading frame, indicating an unusual large number of genes unable to contribute to the accumulation of normal-size 22-kDa zein proteins. It is proposed that the seven remaining zein-related sequences be considered gene reserves because of their potential to be restored by gene conversion. Intergenic insertions in the cluster range from 1098 to 14 896 base pairs. Although they are composed of transposable element sequences, they also contain additional open reading frames, two of them showing homology to rice cDNA sequences. The average amplicon is 4423 base pairs long, with the sequence surrounding each zein gene more than 90 % conserved. Coincidently, the size of the amplicon is equivalent to the average gene density (one gene within 4640 bp) in the Arabidopsis thaliana genome, one of the smallest in plants. Successive steps of amplification and insertion of DNA might explain to a certain degree how genome size variation has been generated in plants.     

Design, synthesis and activity of a potent, selective series of N-aryl pyridinone inhibitors of p38 kinase

A series of N-aryl pyridinone inhibitors of p38 mitogen activated protein (MAP) kinase were designed and prepared based on the screening hit SC-25028 (1) and structural comparisons to VX-745 (5). The focus of the investigation targeted the dependence of potency and metabolic stability on the benzyloxy connectivity, the role of the C-6 position and the substitution pattern on the N-phenyl ring. Further optimization produced the highly selective and potent pyridinones 2 and 3. These inhibitors exhibited activity in both acute and chronic models of inflammation.