African swine fever virus attachment protein.

Treatment of African swine fever virus particles with nonionic detergents released proteins p35, p17, p14, and p12 from the virion. Of these proteins, only p12 bound to virus-sensitive Vero cells but not to virus-resistant L or IBRS2 cells. The binding of p12 was abolished by whole African swine fever virus and not by similar concentrations of subviral particles that lacked the external proteins. A monoclonal antibody (24BB7) specific for p12 precipitated a protein that, when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the absence of 2-mercaptoethanol, showed a molecular mass of 17 kDa (p17*) instead of 12 kDa as found in the presence of 2-mercaptoethanol. The relationship between these two proteins was confirmed by the conversion of p17* to p12 when the former was isolated from polyacrylamide gels in the absence of 2-mercaptoethanol and subsequently treated with the reducing agent. The supernatant obtained after immunoprecipitation with the p12-specific antibody lacked the virus-binding protein.     

Gly-Gly-X, a novel consensus sequence for the proteolytic processing of viral and cellular proteins

Three African swine fever virus structural proteins of relative molecular weights 150,000, 37,000, and 34,000 (p150, p37, and p34) are derived from precursors with relative molecular weights 220,000, 60,000, and 39,000 (pp220, pp60, and pp39) by proteolytic cleavage after the second Gly residue in the sequence Gly-Gly-Ala/Gly. A search of the National Biomedical Research Foundation Data Bank revealed that several adenovirus proteins, ubiquitin, and an interferon-induced 15-kDa protein are also derived from precursors that are cleaved at the sequence Gly-Gly-X, where X is often an amino acid residue with a hydrophobic side chain. The sequence Gly-Gly-X together with other physical properties of the protein seems to be a recognition sequence for the processing of a variety of viral and cellular proteins.     

The influence of two endoparasitic wasps, <Emphasis Type="Italic">Hyposoter didymator</Emphasis> and <Emphasis Type="Italic">Chelonus inanitus</Emphasis>, on the growth and food consumption of their host larva <Emphasis Type="Italic">Spodoptera littoralis</Emphasis>

The influence of parasitism by Hyposoter didymator (Thunberg; Hymenoptera: Ichneumonidae) and Chelonus inanitus (Linnaeus) (Hymenoptera: Braconidae) on the growth and food consumption of their host Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) was studied in the laboratory. Parasitised larvae consumed significantly less artificial diet than unparasitised ones. Egg parasitisation by C. inanitus affected host larval consumption from the second day after emergence and it was significantly different from that of unparasitised ones. H. didymator, however, started to reduce larval consumption 4 days after parasitisation on the third instar host larvae. The overall reduction achieved by the larval endoparasitoid H. didymator is higher than that caused by the egg-larval endoparasitoid C. inanitus. The final body weight of a parasitised host larva by H. didymator and C. inanitus was only 6.7 and 13.0% of the maximum weight of an unparasitised sixth instar larva respectively. Moreover, parasitised larvae never reached the last instar. Results indicated that parasitised larvae might cause considerable less damage to the host plant than unparasitised ones.     

Insecticidal effects of various concentrations of selected extractions of Cestrum parqui on adult and immature Ceratitis capitata

Aqueous extracts of Cestrum parqui L'Héritier (Solanaceae) were evaluated at different concentrations in several stages of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae). For adults, the study was extended to extracts obtained with several solvents of an increasing degree of polarity. Aqueous extracts from C. parqui showed a high toxicity to neonate larvae when ingested through diet, inhibiting pupation at a concentration above 0.6%. Lower concentrations delayed the larval development and reduced the percentages of pupae formed and adult emergence. An LC50 = 0.9% after 3 d of continuous ingestion of C. parqui aqueous extracts could be calculated, whereas extracts obtained with organic compounds were nearly innocuous except with the use of the solvent methanol/water (80:20), the more polar of those tested, that killed 12.5% of adults. Aqueous extracts were also harmful to adults by diminishing the reproductive potential, which implies a significant effect on the offspring. Egg contact with insecticide or dipping third instars did not cause any adverse effect, supporting the hypothesis that only by means of ingestion can the toxic compounds of C. parqui reach the target. Our results showed that C. parqui components causing C. capitata mortality are mostly dissolved in water and not in organic solvents, which point out their polar character.     

Genetic and physical localization of the soybean Rpg1-b disease resistance gene reveals a complex locus containing several tightly linked families of NBS-LRR genes

Alleles or tightly linked genes at the soybean (Glycine max L. Merr.) Rpg1 locus confer resistance to strains of Pseudomonas syringae pv. glycinea that express the avirulence genes avrB or avrRpm1. We have previously mapped Rpg1-b (the gene specific for avrB) to a cluster of resistance genes (R genes) with diverse specificities in molecular linkage group F. Here, we describe the high-resolution physical and genetic mapping of Rpg1-b to a 0.16-cM interval encompassed by two overlapping BAC clones spanning approximately 270 kilobases. Rpg1-b is part of a complex locus containing numerous genes related to previously characterized coiled coil-nucleotide binding site-leucine rich repeat (CC-NBS-LRR)-type R genes that are spread throughout this region. Phylogenetic and Southern blot analyses group these genes into four distinct subgroups, some of which are conserved in the common bean, Phaseolus vulgaris, indicating that this R gene cluster may predate the divergence of Phaseolus and Glycine. Members from different subgroups are physically intermixed and display a high level of polymorphism between soybean cultivars, suggesting that this region is rearranging at a high frequency. At least five CC-NBS-LRR-type genes cosegregate with Rpg1-b in our large mapping populations.     

Migration of Mitochondria to Viral Assembly Sites in African Swine Fever Virus-Infected Cells

An examination by electron microscopy of the viral assembly sites in Vero cells infected with African swine fever virus showed the presence of large clusters of mitochondria located in their proximity. These clusters surround viral factories that contain assembling particles but not factories where only precursor membranes are seen. Immunofluorescence microscopy revealed that these accumulations of mitochondria are originated by a massive migration of the organelle to the virus assembly sites. Virus infection also promoted the induction of the mitochondrial stress-responsive proteins p74 and cpn 60 together with a dramatic shift in the ultrastructural morphology of the mitochondria toward that characteristic of actively respiring organelles. The clustering of mitochondria around the viral factory was blocked in the presence of the microtubule-disassembling drug nocodazole, indicating that these filaments are implicated in the transport of the mitochondria to the virus assembly sites. The results presented are consistent with a role for the mitochondria in supplying the energy that the virus morphogenetic processes may require and make of the African swine fever virus-infected cell a paradigm to investigate the mechanisms involved in the sorting of mitochondria within the cell.     

Analysis of a laboratory method to test the effects of pesticides on adult females of Opius concolor (Hym., Braconidae), a parasitoid of the olive fruit fly,Bactrocera oleae (Dip., Tephritidae)

The laboratory test described in the present paper assesses pesticide effects on the ‘most exposed’ life stage of the parasitic wasp Opius concolor, and it has been developed and interpreted according to the guidelines of the IOBC/WPRS Working Group ‘Pesticides and Beneficial Organisms ‘. The evaluation of results is based on longevity and parasitism of adult females exposed to afresh residue of pesticide on a glass surface. Longevity measurements were based on the time of exposure required to cause 50% mortality (LT₅₀) and were compared to a standard control LT₅₀ in order to calculate the reduction caused by the pesticide. Parasitism was surveyed by means of three sequential determinations: the number of days that females were seen parasitizing, the mean number of attacked hosts and the progeny size per female. These determinations were also compared to a control to calculate the impact of pesticides. Using this ‘worst case’ situation, pesticides reducing the beneficial capacity of O. concolor below the IOBC threshold for harmlessness may be recommended for field use in combination with this wasp.     

Order of the two major head protein genes of bacteriophage phi 29 of Bacillus subtilis.

Bacteriophage phi 29 mutation sus8(22) has been mapped by two-factor crosses between markers sus8(769) and ts8(93). Whe sus8(22) infects Bacillus subtilis su- proteins, HP1 (major head protein) and HP3 (fiber protein) are not synthesized; instead, a fragment with a molecular weight of 25,000 is produced. The tryptic peptides of the fragments overlap with corresponding peptides in protein HP1, but not with the peptides of protein HP3, showing that cistron 8 codes for the major head protein HP1.     

Assembly of Bacillus subtilis phage phe29. 2. Mutants in the cistrons coding for the non-structural proteins.

The effect on phage morphogenesis of sus mutations in the cistrons coding for nonstructural proteins has been studied. Mutants in three cistrons analyzed that are involved in phage DNA synthesis, as well as in cistron 16 which codes for a late nonstructural protein, produce prolate capsids which are more rounded at the corners than complete phage heads and have an internal core; they contain the head proteins, the upper collar protein and protein p7, not present in mature phage particles. Mutants in cistron 7 do not produce capsids nor other phage-related structures; this result and the presence of p7 in phage capsids suggest an essential role in capsid assembly for this protein. The protein product of cistron 13 is probably needed for a stable DNA encapsulation since mutants in this cistron produce mainly DNA-free complete phage particles and only about 10% of uninfective DNA-containing complete phage. Cistron 15 codes for a late, partially dispensable, nonstructural protein which is present in the DNA-free capsids produced after infection with the delayed-lysis mutant sus14(1242), used as the wild-type control, or with mutants in cistrons 9, 11,12 and 13. Proteins p15 and p16 are probably involved in the encapsulation of viral DNA in a prohead.