Structural and functional characterization of pseudopodocyte, a shaggy immune cell produced by two Drosophila species of the obscura group.

We recently reported that most of the Drosophila species of the obscura group were unable to mount cellular capsules and no lamellocyte was ever found in the hemolymph of any of the tested species. Only three species were able to encapsulate, despite lacking lamellocytes. Their encapsulation ability was always associated with the presence of an unpreviously described kind of capsule-forming immunocytes designated as "atypical hemocytes".

Spodoptera frugiperda X-tox protein, an immune related defensin rosary, has lost the function of ancestral defensins.

Background: X-tox proteins are a family of immune-related proteins only found in Lepidoptera and characterized by imperfectly conserved tandem repeats of several defensin-like motifs. Previous phylogenetic analysis of X-tox genes supported the hypothesis that X-tox have evolved from defensins in a lineage-specific gene evolution restricted to Lepidoptera. In this paper, we performed a protein study in which we asked whether X-tox proteins have conserved the antimicrobial functions of their ancestral defensins and have evolved as defensin reservoirs.

The emerging human pathogen Photorhabdus asymbiotica is a facultative intracellular bacterium and induces apoptosis of macrophage-like cells.

Photorhabdus species are gram-negative entomopathogenic bacteria of the family Enterobacteriaceae. Among the different members of the genus, one species, Photorhabdus asymbiotica, is a pathogen of both insects and humans. The pathogenicity mechanisms of this bacterium are unknown.

Effect of a toxicant on phagocytosis pathways in the freshwater snail Lymnaea stagnalis.

The disturbance of plasma membrane carbohydrates and of lipopolysaccharide (LPS) ligands in relation to cytoskeletal transformations of haemocytes has been investigated after chronic exposure of pond snails (Lymnaea stagnalis) to the peroxidizing toxicant fomesafen. Neither of the two lectins used (concanavalin A and wheat germ agglutinin) showed any binding modification after incubation of the snails in the presence of the toxicant. However, after exposure of the snails to fomesafen, a clear and persistent reduction in LPS labelling of haemocytes occurred.

X-tox: an atypical defensin derived family of immune-related proteins specific to Lepidoptera.

We report here the isolation in Spodoptera frugiperda (Lepidoptera) of an immune-related protein (hereafter named Spod-11-tox), characterized by imperfectly conserved tandem repeats of 11 cysteine-stabilized alpha beta motifs (CS-alphabeta), the structural scaffold characteristic of invertebrate defensins and scorpion toxins. Spod-11-tox orthologs were only found in Lepidopteran species, suggesting that this new protein family (named X-tox) is specific to this insect order. Moreover, phylogenetic analysis suggests that X-tox proteins represent a new class of proteins restricted to Lepidoptera and likely derived from Lepidopteran defensins.

The xaxAB genes encoding a new apoptotic toxin from the insect pathogen Xenorhabdus nematophila are present in plant and human pathogens.

Xenorhabdus nematophila, a member of the Enterobacteriaceae, kills many species of insects by strongly depressing the immune system and colonizing the entire body. A peptide cytotoxin has been purified from X. nematophila broth growth, and the cytolytic effect on insect immunocytes and hemolytic effect on mammalian red blood cells of this toxin have been described (Ribeiro, C.

Insect haemocytes: what type of cell is that?

Classification of insect larvae circulating haemocytes is the subject of controversy, and the terminology used to designate each cellular type is often different from one species to another. However, a survey of the literature on insect haemocytes suggests that there are resemblances for most of the cell types and functions, in different insect species. In this review paper, we compare the structure and functions of circulating haemocytes in those insect species that are, by far, the most often used species for insect physiology studies, i.

Modes of phagocytosis of Gram-positive and Gram-negative bacteria by Spodoptera littoralis granular haemocytes.

Haemocytes are the main immunocompetent cells in insect cellular immune reactions. Here, we show that in Spodoptera littoralis, granular haemocytes are the primary phagocyte haemocytes, both in vivo and in vitro. The "trigger" and "zipper" modes of engulfment known in mammal macrophages are active, in vivo, in S.

Site-specific antiphagocytic function of the Photorhabdus luminescens type III secretion system during insect colonization.

Photorhabdus is an entomopathogenic bacterium belonging to the Enterobacteriaceae. The genome of the TT01 strain of Photorhabdus luminescens was recently sequenced and a large number of toxin-encoding genes were found. Genomic analysis predicted the presence on the chromosome of genes encoding a type three secretion system (TTSS), the main role of which is the delivery of effector proteins directly into eukaryotic host cells.

Stages of infection during the tripartite interaction between Xenorhabdus nematophila, its nematode vector, and insect hosts.

Bacteria of the genus Xenorhabdus are mutually associated with entomopathogenic nematodes of the genus Steinernema and are pathogenic to a broad spectrum of insects. The nematodes act as vectors, transmitting the bacteria to insect larvae, which die within a few days of infection. We characterized the early stages of bacterial infection in the insects by constructing a constitutive green fluorescent protein (GFP)-labeled Xenorhabdus nematophila strain.

Insect immunity-effects of factors produced by a nematobacterial complex on immunocompetent cells(1).

During in vitro incubations, the nematobacterial complex Steinernema carpocapsae-Xenorhabdus nematophilus produces different factors having toxic activities in vitro towards haemocytes, the insect cells responsible for cellular immune defense reactions. Among others, two effects were evident on haemocyte monolayers; one of them was a cytotoxic activity while the other was an unsticking effect. The factors responsible for cytotoxic activity and unsticking effect, were separated from each other by a single chromatography on anion exchange column.

Xenorhabdus nematophila (enterobacteriacea) secretes a cation-selective calcium-independent porin which causes vacuolation of the rough endoplasmic reticulum and cell lysis.

Xenorhabdus nematophila and Photorhabdus luminescens are two related enterobacteriaceae studied for their use in biological control and for synthesis of original virulence factors and new kinds of antibiotics. X. nematophila broth growth exhibits different cytotoxic activities on insect (Spodoptera littoralis, lepidoptera) immunocytes (hemocytes).

Two distinct hemolytic activities in Xenorhabdus nematophila are active against immunocompetent insect cells.

Xenorhabdus spp. and Photorhabdus spp. are major insect bacterial pathogens symbiotically associated with nematodes.

The plcR regulon is involved in the opportunistic properties of Bacillus thuringiensis and Bacillus cereus in mice and insects.

Bacillus thuringiensis has been widely used for 40 years as a safe biopesticide for controlling agricultural pests and mosquitoes because it produces insecticidal crystal proteins. However, spores have also been shown to contribute to overall entomopathogenicity. Here, the opportunistic properties of acrystalliferous B.

Haemocyte changes in resistant and susceptible strains of D. melanogaster caused by virulent and avirulent strains of the parasitic wasp Leptopilina boulardi.

Two strains of Drosophila melanogaster (resistant and susceptible) were parasitized by a virulent or avirulent strain of the parasitoid wasp Leptopilina boulardi. The success of encapsulation depends on both the genetic status of the host strain and the genetic status of the parasitoid strain: the immune cellular reaction (capsule) is observed only with the resistant strain-avirulent strain combination. The total numbers of host haemocytes increased in all 4 combinations, suggesting that an immune reaction was triggered in all hosts.

Low molecular weight serine protease inhibitors from insects are proteins with highly conserved sequences.

A low molecular weight protease inhibitor peptide found in ovaries of the desert locust Schistocerca gregaria (SGPI-2), was purified from plasma of the same locust and sequenced. It was named SGCI. It was found active towards chymotrypsin and human leukocyte elastase.

[Cellular defence reactions and their depression in insects].

In insects the main cellular defence reactions are phagocytosis and encapsulation of foreign bodies. Free cells of haemolymph called haemocytes are the effectors of these reactions. They are achieved under the control of humoral factors of the plasma or of the serum.

Two major proteins from locust plasma are involved in coagulation and are specifically precipitated by laminarin, a beta-1,3-glucan.

Incubation of plasma of the locust Locusta migratoria, with laminarin induced the precipitation of two major proteins with molecular masses of about 260,000 (P260) and 85,000 Da (P85). This precipitation was not observed when other polysaccharides, such as curdlan, dextran, chitin, cellulose or mannan were used. P260 and P85 were purified to homogeneity by a single step on heparin-sepharose chromatography.

Cooperation of dopachrome conversion factor with phenoloxidase in the eumelanin pathway in haemolymph of Locusta migratoria (Insecta).

Dopachrome Conversion Factor (DCF) was found in the plasma of the locust Locusta migratoria. It has an apparent molecular mass of 85,000. Its K(m) was 0.

Immune suppressive virus-like particles in a Drosophila parasitoid: significance of their intraspecific morphological variations.

The Eucoilid parasitoid Leptopilina boulardi is able to suppress its host Drosophila melanogaster immune reaction. Some strains, however, are non-immune suppressive to that host. Virus-like particles (VLPs) responsible for the immune suppressive ability were investigated in different strains of L.

Insect immunity: early events in the encapsulation process of parasitoid (Leptopilina boulardi) eggs in resistant and susceptible strains of Drosophila.

Eggs of an immune suppressive strain (= virulent) of the parasitoid Leptopilina boulardi are encapsulated neither in resistant nor in susceptible strains of Drosophila melanogaster but are encapsulated in Drosophila yakuba. Eggs of a nonimmune suppressive strain (= avirulent) of the same parasitoid are encapsulated in a resistant strain of D. melanogaster and in D.

Insect immunity: two proteinase inhibitors from hemolymph of Locusta migratoria.

Two protease inhibitors were isolated from the plasma of Locusta migratoria and sequenced. They were 35 and 36 amino acids long and revealed very little similitude for the protease inhibitors isolated from other arthropods. They inhibit the proPhenoloxidase Phenoloxidase proteolytic activation cascade in hemocyte extracts of the same insect.

Lysogeny and bacteriocinogeny in Xenorhabdus nematophilus and other Xenorhabdus spp.

Induction by mitomycin or high-temperature treatment resulted in the production of bacteriocins and phages in both phases of Xenorhabdus nematophilus A24, indicating lysogeny. Phage DNA purified from X. nematophilus A24 hybridized to several fragments of DraI-digested A24 chromosomal DNA, confirming that the phage genome was incorporated into the bacterial chromosome.

Purification of a protease inhibitor which controls prophenoloxidase activation in hemolymph of Locusta migratoria (insecta).

A protein which inhibits the prophenoloxidase----phenoloxidase (EC 1.14.18.