Oviposition sequence and offspring of mated and virgin females of Cotesia flavipes (hymenoptera: braconidae) parasitizing Diatraea saccharalis larvae (lepidoptera: crambidae)

Large scale mass rearing of natural enemies has been a mean of improving biological control in the sugarcane intensive agriculture. Among them, Cotesia flavipes, a gregarious koinobiont endoparasitoid, was imported by Brasil to control caterpillars of the sugarcane borer Diatraea saccharalis. The C. flavipes larval development depends on its association with polydnavirus, which blocks the host defense reaction. To verify if the oviposition sequence (1st, 2nd or 3rd) and the female condition (mated or virgin) interfere in the number of C. flavipes descendents, 4th instar caterpillars of D. saccharalis were parasitized. Analysis of the data showed that: a) there is an inverse correlation between the parasitism efficiency and the host reaction (encapsulation); b) the number of caterpillars parasitized by virgin females that released parasitoid larvae in the period from 12 to 15 days was higher than that of caterpillars parasitized by mated females; c) a slight difference between mated and virgin females in relation to the parasitim success was observed; and d) the number of encapsulated parasitoid larvae was higher than that of eggs, suggesting that eggs have a better capacity to overcome the host reaction. In this study, the viability of C. flavipes eggs and larvae in the non-specific host D. saccharalis could be correlated with the oviposition sequence and the female condition

A new firefly luciferase with bimodal spectrum: identification of structural determinants of spectral pH-sensitivity in firefly luciferases.

Fireflies emit flashes in the green-yellow region of the spectrum for the purpose of sexual attraction. The bioluminescence color is determined by the luciferases. It is well known that the in vitro bioluminescence color of firefly luciferases can be shifted toward the red by lower pH and higher temperature; for this reason they are classified as pH-sensitive luciferases. However, the mechanism and structural origin of pH sensitivity in fireflies remains unknown. Here we report the cloning of a new luciferase from the Brazilian twilight active firefly Macrolampis sp2, which displays an unusual bimodal spectrum. The recombinant luciferase displays a sensitive spectrum with the peak at 569 nm and a shoulder in the red region. Comparison of the bioluminescence spectra of Macrolampis, Photinus and Cratomorphus firefly luciferases shows that the distinct colors are determined by the ratio between green and red emitters under luciferase influence. Comparison of Macrolampis luciferase with the highly similar North American Photinus pyralis luciferase (91%) showed few substitutions potentially involved with the higher spectral sensitivity in Macrolampis luciferase. Site-directed mutagenesis showed that the natural substitution E354N determines the appearance of the shoulder in the red region of Macrolampis luciferase bioluminescence spectrum, helping to identify important interactions and residues involved in the pH-sensing mechanism in firefly luciferases.

Haemolymph electrophoretic pattern of Ascia monuste orseis larvae (Lepidoptera: Pieridae) parasitized by Cotesia glomerata (Hymenoptera: Braconidae)

Cotesia glomerata is a natural enemy of the vegetable plague Ascia monuste orseis and preferably parasites 2nd, 3rd and 4th instar larvae. Parasitism effects on the haemolymph protein profile of Ascia monuste orseis larvae from the 2nd to 7th days were analyzed both qualitatively and quantitatively by SDS-PAGE and Coomassie-Blue binding methods. Quantitative analysis showed a progressive increase in the protein content of about 6.5 and 12.5 times in parasitized and non-parasitized larvae from the 2nd to 5th days, respectively. On the 6th day, a decrease in protein content was observed in both groups, although this decrease was significantly less than the control group that continued to metamorphosis. Meanwhile, parasitized larvae had one more day (7th day) in their larval period to complete parasitoid development, justified by the fact that parasitoid is koinobiont and allows host feeding. On this day, a drastic increase in protein content was detected when the parasitoids left the host. The SDS-PAGE showed proteins of high molecular weight (>120 kDa) on the 5th day of the non-parasitized larvae when they entered pre-pupa stage and on the 7th day of parasitized larvae. Proteins with MW lower than 62 kDa and higher than 27 kDa were absent on the 5th day in control larvae (pre-pupa phase), but present in parasitized larvae. This could indicate a possible relation between these proteins and the host juvenile hormone. Therefore, the presence of C. glomerata influences Ascia monuste orseis development, but its own physiological development is apparently independent of the host, which tends to die when parasitism succeeds.

Hymenoptera venom review focusing on Apis mellifera

Hymenoptera venoms are complex mixtures containing simple organic molecules, proteins, peptides, and other bioactive elements. Several of these components have been isolated and characterized, and their primary structures determined by biochemical techniques. These compounds are responsible for many toxic or allergic reactions in different organisms, such as local pain, inflammation, itching, irritation, and moderate or severe allergic reactions. The most extensively characterized Hymenoptera venoms are bee venoms, mainly from the Apis genus and also from social wasps and ant species. However, there is little information about other Hymenoptera groups. The Apis venom presents high molecular weight molecules - enzymes with a molecular weight higher than 10.0 kDa - and peptides. The best studied enzymes are phospholipase A2, responsible for cleaving the membrane phospholipids, hyaluronidase, which degrades the matrix component hyaluronic acid into non-viscous segments and acid phosphatase acting on organic phosphates. The main peptide compounds of bee venom are lytic peptide melittin, apamin (neurotoxic), and mastocyte degranulating peptide (MCD).

Protein requirements in larvae and adults of Scaptotrigona postica (Hymenoptera: Apidae [correction of Apidia], Meliponinae): midgut proteolytic activity and pollen digestion.

The number and degree of digestion of pollen grains in the midgut and rectum, the midgut proteolytic activity and the time of pollen grain passage through the digestive tract in the stingless bee Scaptotrigona postica (Latreille) have been analyzed. The results show similar protein requirements among larvae, nurse bees and queens, as well as between forager bees and old males, but these requirements are higher in individuals from the former groups than in those from the latter. Although protein requirements have been demonstrated to vary according to a bee's activity in the colony, they are similar among bees from different castes or sexes. These changes in feeding behavior are related to the bee's function and to less competition for nourishment among individuals of the colony. It is also noted that pollen grains took between 6 and 28 h to pass through the digestive tract. Pollen grains are irregularly accumulated in the various regions of the midgut, which may reflect functional differentiation throughout the midgut.

Molecular exclusion chromatography of crude venom as an auxiliary tool to identify hybrid honeybee populations

A comparison among the profiles of molecular exclusion chromatography in Sephadex G 100 column of venoms from Apis mellifera adansonii and Africanized honeybees revealed unique peaks which might be used to identify these populations. The venoms from hybrid populations resulting from the reciprocal mating of Apis mellifera adansonii and Africanized honeybees presented unique peaks, probably resulting from a synergistic effect between the parental genomes. The occurrence of characteristic peaks in venoms of hybrid populations might be used to identify these populations as well as to distinguish them from their parents.

The effect of a polydnavirus of Apanteles Galleriae on the hemolymph proteins of host Galleria Mellonela

The presence of a polydnavirus in the ovary of the microhymennoptera Apanteles galleriae was detected. This wasp parasites the larvae of the wax moth Galleria mellonella. To study the possible viral effects on the total protein of G. mellonella, hemolymph extracts of the ovary calyxes of parasitized A. galleriae were injected into 6th and 7th instar cells of G. mellonella larvae. Protein profiles on polyacrilamide gel electrophoresis containing sodium dodecyl sulfate (SDS-PAGE) of host cell extracts showed a suppression of several protein bands when infection occurred in the 6th instar. However, in the 7th instar, parasitism caused an amplification in the synthesis of most proteins with some changes in the electrophoretic profile.

Biochemical properties and study of antigenic cross-reactivity between Africanized honey bee and wasp venom.

Africanized honey bees and the wasp Polistes versicolor are common insects in Brazil; their venoms are composed of a complex mixture of components which present several biological activities. Stinging accidents are very frequent and are generally followed by important clinical reactions, and even deaths are not uncommon. In the present study, venom was extracted from Africanized honey bees and P. versicolor, and it was biochemically characterized and the antigenic cross-reactivity was investigated by Western blot analysis and specific IgE determination by ELISA in the sera of subjects allergic to each venom. The honey bee venom presented higher phospholipase A2 and hyaluronidase activities than P. versicolor venom, which in turn presented higher lipase, acid phosphatase and esterase activities. A high incidence of false-negatives was also observed during determinations of specific IgE for P. versicolor venom when the kits with venoms from wasps of temperate climates were used, suggesting that the diagnosis of allergy to neotropical wasp venom must take into consideration the clinical history and skin tests.

Partial purification and characterization of lysine-ketoglutarate reductase in normal and opaque-2 maize endosperms.

Lysine-ketoglutarate reductase catalyzes the first step of lysine catabolism in maize (Zea mays L.) endosperm. The enzyme condenses l-lysine and alpha-ketoglutarate into saccharopine using NADPH as cofactor. It is endosperm-specific and has a temporal pattern of activity, increasing with the onset of kernel development, reaching a peak 20 to 25 days after pollination, and there-after decreasing as the kernel approaches maturity. The enzyme was extracted from the developing maize endosperm and partially purified by ammonium-sulfate precipitation, anion-exchange chromatography on DEAE-cellulose, and affinity chromatography on Blue-Sepharose CL-6B. The preparation obtained from affinity chromatography was enriched 275-fold and had a specific activity of 411 nanomoles per minute per milligram protein. The native and denaturated enzyme is a 140 kilodalton protein as determined by polyacrylamide gel electrophoresis. The enzyme showed specificity for its substrates and was not inhibited by either aminoethyl-cysteine or glutamate. Steady-state product-inhibition studies revealed that saccharopine was a noncompetitive inhibitor with respect to alpha-ketoglutarate and a competitive inhibitor with respect to lysine. This is suggestive of a rapid equilibrium-ordered binding mechanism with a binding order of lysine, alpha-ketoglutarate, NADPH. The enzyme activity was investigated in two maize inbred lines with homozygous normal and opaque-2 endosperms. The pattern of lysine-ketoglutarate reductase activity is coordinated with the rate of zein accumulation during endosperm development. A coordinated regulation of enzyme activity and zein accumulation was observed in the opaque-2 endosperm as the activity and zein levels were two to three times lower than in the normal endosperm. Enzyme extracted from L1038 normal and opaque-2 20 days after pollination was partially purified by DEAE-cellulose chromatography. Both genotypes showed a similar elution pattern with a single activity peak eluted at approximately 0.2 molar KCL. The molecular weight and physical properties of the normal and opaque-2 enzymes were essentially the same. We suggest that the Opaque-2 gene, which is a transactivator of the 22 kilodalton zein genes, may be involved in the regulation of the lysine-ketoglutarate reductase gene in maize endosperm. In addition, the decreased reductase activity caused by the opaque-2 mutation may explain, at least in part, the elevated concentration of lysine found in the opaque-2 endosperm.