De speurneus van een sluipwesp

Sluipwespen zijn de bekendste biologische bestrijders. Met gewone wespen hebben deze diertjes niets te maken. Het zijn kleine, tengere insecten die heel goed zijn in het opsporen van hun slachtoffers. Die slachtoffers - of beter gezegd, gastheren waar zij hun eitjes in kunnen leggen - zijn meestal de goed gecamoufleerde eitjes of rupsen van vlinders. Eigenlijk is het een wonder dat de sluipwespen die slachtoffers zo goed weten te vinden op de oneindige akkers. Bij het zoeken naar eitjes en rupsen maken sluipwespen vooral gebruik van hun reukvermogen. De planten waarvan ze eten produceren een kenmerkende geur die alleen wordt afgegeven als er insecten van de plant eten. De geuren die een plant produceert bij insectenvraat zijn vaak specifiek voor de soort of zelfs de leeftijd van de rups die op de plant zit. Een sluipwesp kan dus van een afstand ruiken welke gastheer er op een plant te vinden i

A peptide from the male accessory glands of the Colorado potato beetle

This thesis describes a study of the male accessory glands of the Colorado potato beetle, Leptinotarsa decemlineata (Say). These glands add various substances to the ejaculate. On mating, the ejaculate is transferred to the female, together with the substances from the male accessory glands. The function of these substances is unknown in the case of the Colorado potato beetle. From research on other insect species, we know that some of these substances stimulate the female to oviposit at a higher rate, and to refuse further matings for a certain period. These two effects are known to be evoked by the action of one peptide hormone in the case of Drosophila melanogaster , and this peptide is called sex-peptide. At least part of its activity is thought to be accomplished by stimulation of the corpus allatum (allatotropic) activity, as indicated by in vitro experiments. The activity of the corpora allata is normally under control of some neurons in the brain, the lateral neurosecretory cells, which innervate these glands. These neurons use as yet unidentified peptide hormones as messenger substance, and it is possible that these peptides are similar in structure and activity to sex-peptide.Our immunohistochemical studies on the Colorado potato beetle give indirect support for the possible dual control of corpus allutm activity. We revealed that some glandular cells in the male accessory glands are labelled by a monoclonal antibody that was raised against the peptides in the lateral neurosecretory cells. The question arises whether the antigen in the accessory glands is indeed identical to the antigen in the lateral neurosecretory cells. In that case, both antigens are involved in stimulation of the corpus allatum activity. The aim of the present study is to compare the antigens in the accessory glands and the lateral neurosecretory cells, and to study the function of the former in more detail (chapter 1).The antigen in each of the two accessory glands is present in a specific set of approximately 100 dispersed glandular cells. The immuno-reactive cells contain granules with crystalline contents, and these crystals have a rod-like appearance. Such rods are also immuno-labelled in the lumen of the gland (chapter 2).The antigen in the accessory glands is a peptide of 8 kDa., designated Led-MAGP ( Le ptinotarsa d ecemlineatam ale a ccessory g land p eptide). Part of the amino acid sequence has been determined. Using this structural information the gene encoding this peptide has been identified and thereby the structure of the entire peptide. The peptide is expressed exclusively in the accessory glands, not in the brains. The peptide does not resemble any known peptide hormone, but it shows a considerable degree of similarity to the N-terminus of the chicken prion protein. Prion proteins are at present in the centre of interest since they are involved in certain fatal neurodegenerative diseases in man (Creutzfeldt-Jakob disease) and cattle (scrapie, bovine spongiformic encephalopathies, better known by its acronym BSE) (chapter 3).Four antigens from the lateral neurosecretory cells have been characterized to determine their relatedness to Led-MAGP. However, the peptides isolated all differ in size and chromatographic properties from Led-MAGP. Our initial interpretation that the antigens from the lateral neurosecretory cells might be identical to Led-MAGP, had therefore to be rejected (chapter 4).A recombinant baculovirus is constructed, equipped with the gene encoding Led-MAGP. This way large amounts of this peptide are produced in order to study its function. The recombinant Led-MAGP is produced by infection of insect cells cultures with the recombinant baculovirus. Large scale production is hampered by the formation of large aggregates of Led-MAGP. Nevertheless, sufficient peptide has been harvested to produce a new antibody against Led-MAGP. This antibody recognized the authentic peptide with superior specificity, compared with the monoclonal antibody used previously (chapter 5).Microscopical analysis with the new antiserum reveals the fate of Led-MAGP during copulation. Male and female reproductive tracts were taken from mating couples for immunohistochemical analysis with the new antiserum. The route of the Led-MAGP could be analyzed in detail. Led-MAGP is transferred from the male accessory glands to the spermathecal duct in the female. Led-MAGP most probably diffuses to the hemolymph within minutes after its deposition (chapter 6).A hypothesis is put forward as to the physiological function of Led-MAGP. This hypothesis is based on the homology of Led-MAGP with the chicken prion protein, and on the observation that it binds hemolymph protein. The N-terminus of the chicken prion protein namely contains 8 hexa-repeats, whereas Led-MAGP has and 7 hexa-repeats that are largely homlogous. Although the biological function of the prion protein itself is unknown, the section with the 8 hexarepeats serves as a signal that induces the uptake of the ch-prp in the endocytosis route. By analogy, Led-MAGP could, by binding to hemolymph proteins, induce the uptake of these proteins by the developing oocytes. This way led-MAGP stimulates the growth of the oocytes on the expense of female hemolymph proteins. In other words, the balance of protein use between maintenance and reproduction, is shifted more towards reproduction. This mechanism would at the same time explain the reduction of female receptivity for mating, as remating will lead to the acquisition of too much Led-MAGP, and thus to overstimulation of reproduction at the expense of other body functions (chapter 7).A test of the hypothesis that is proposed in chapter 7 awaits methodological improvements. Detection of Led-MAGP in the mated female, by using the specific antiserum is hampered due to cross-reactivity of several female-derived proteins. The tendency of Led-MAGP to aggregate further complicates a functional analysis. Furthermore, the available inbred laboratory strain of the Colorado potato beetle is probably unsuitable for a bioassay on stimulation of oviposition (general discussion).</p

Herbivore-induced plant volatiles mediate in-flight host discrimination by parasitoids

Herbivore feeding induces plants to emit volatiles that are detectable and reliable cues for foraging parasitoids, which allows them to perform oriented host searching. We investigated whether these plant volatiles play a role in avoiding parasitoid competition by discriminating parasitized from unparasitized hosts in flight. In a wind tunnel set-up, we used mechanically damaged plants treated with regurgitant containing elicitors to simulate and standardize herbivore feeding. The solitary parasitoid Cotesia rubecula discriminated among volatile blends from Brussels sprouts plants treated with regurgitant of unparasitized Pieris rapae or P. brassicae caterpillars over blends emitted by plants treated with regurgitant of parasitized caterpillars. The gregarious Cotesia glomerata discriminated between volatiles induced by regurgitant from parasitized and unparasitized caterpillars of its major host species, P. brassicae. Gas chromatography-mass spectrometry analysis of headspace odors revealed that cabbage plants treated with regurgitant of parasitized P. brassicae caterpillars emitted lower amounts of volatiles than plants treated with unparasitized caterpillars. We demonstrate (1) that parasitoids can detect, in flight, whether their hosts contain competitors, and (2) that plants reduce the production of specific herbivore-induced volatiles after a successful recruitment of their bodyguards. As the induced volatiles bear biosynthetic and ecological costs to plants, downregulation of their production has adaptive value. These findings add a new level of intricacy to plant¿parasitoid interaction

Transcriptomic properties of her2+ ductal carcinoma in situ of the breast associate with absence of immune cells

SIMPLE SUMMARY: Tumor-infiltrating lymphocytes (TILs) are likely to play a role in the biological behavior of HER2+ ductal carcinoma in situ (DCIS). To prevent invasiveness, the potential of targeted immune-modulating treatment of HER2+ DCIS has been explored. We identified a 29-gene expression profile that was associated with the density of TILs. These genes included CCND3, DUSP10 and RAP1GAP, which may guide towards more rationalized choices with respect to immune-mediated therapy in HER2+ DCIS, such as targeted vaccine therapy. ABSTRACT: The identification of transcriptomic alterations of HER2+ ductal carcinoma in situ (DCIS) that are associated with the density of tumor-infiltrating lymphocytes (TILs) could contribute to optimizing choices regarding the potential benefit of immune therapy. We compared the gene expression profile of TIL-poor HER2+ DCIS to that of TIL-rich HER2+ DCIS. Tumor cells from 11 TIL-rich and 12 TIL-poor DCIS cases were micro-dissected for RNA isolation. The Ion AmpliSeq Transcriptome Human Gene Expression Kit was used for RNA sequencing. After normalization, a Mann–Whitney rank sum test was used to analyze differentially expressed genes between TIL-poor and TIL-rich HER2+ DCIS. Whole tissue sections were immunostained for validation of protein expression. We identified a 29-gene expression profile that differentiated TIL-rich from TIL-poor HER2+ DCIS. These genes included CCND3, DUSP10 and RAP1GAP, which were previously described in breast cancer and cancer immunity and were more highly expressed in TIL-rich DCIS. Using immunohistochemistry, we found lower protein expression in TIL-rich DCIS. This suggests regulation of protein expression at the posttranslational level. We identified a gene expression profile of HER2+ DCIS cells that was associated with the density of TILs. This classifier may guide towards more rationalized choices regarding immune-mediated therapy in HER2+ DCIS, such as targeted vaccine therapy

Comprehensive evaluation of methods to assess overall and cell-specific immune infiltrates in breast cancer

Background: Breast cancer (BC) immune infiltrates play a critical role in tumor progression and response to treatment. Besides stromal tumor infiltrating lymphocytes (sTILs) which have recently reached level 1B evidence as a prognostic marker in triple negative BC, a plethora of methods to assess immune infiltration exists, and it is unclear how these compare to each other and if they can be used interchangeably. Methods: Two experienced pathologists scored sTIL, intra-tumoral TIL (itTIL), and 6 immune cell types (CD3+, CD4+, CD8+, CD20+, CD68+, FOXP3+) in the International Cancer Genomics Consortium breast cancer cohort using hematoxylin and eosin-stained (n = 243) and immunohistochemistry-stained tissue microarrays (n = 254) and whole slides (n = 82). The same traits were evaluated using transcriptomic- and methylomic-based deconvolution methods or signatures. Results: The concordance correlation coefficient (CCC) between pathologists for sTIL was very good (0.84) and for cell-specific immune infiltrates slightly lower (0.63-0.66). Comparison between tissue microarray and whole slide pathology scores revealed systematically higher values in whole slides (ratio 2.60-5.98). The Spearman correlations between microscopic sTIL and transcriptomic- or methylomic-based assessment of immune infilt