Pre‐copulation intervals,copulation frequencies,and initial progeny sex ratios in two biotypes of whitefly,Bemisia tabaci

The whitefly Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) is a species complex, and its systematic classification requires controlled crossing experiments among its genetic groups. Accurate information on pre‐copulation intervals, copulation frequencies, and initial frequency of egg fertilization of newly emerged adults is critical for designing procedures for collecting the virgin adults necessary for these experiments. In the literature, considerable variation is reported between B. tabaci populations, with respect to the length of the pre‐copulation interval and the initial frequency of egg fertilization. Here, we used a video‐recording method to observe continuously the copulation behaviour of the Mediterranean/Asia Minor/Africa (B biotype) and the Asia II (ZHJ1 biotype) groups of B. tabaci. We also recorded the initial frequency of egg fertilization, as determined by the sex of the progeny. When adults were caged in female–male pairs on leaves of cotton plants, the earliest copulation events occurred 2–6 h after emergence; at 12 h after emergence 56–84% of the females had copulated at least once, and nearly all (92–100%) had copulated at least once by 36 h after emergence. Both females and males copulated repeatedly. Approximately 80 and 20% of copulation events occurred during the photophase and scotophase, respectively. By 72 h post‐emergence, the females of the B and ZHJ1 biotypes had copulated on average 6.1 and 3.9 times, respectively. When adults were caged in groups on plants 1–13 h after emergence, 30–35% of the eggs deposited during this period were fertilized, and approximately 90% of females were fertilized by the end of the 13 h. Although timing of copulation differed in detail between the two genetic groups, the results demonstrate that B. tabaci adults can start to copulate as early as 2–6 h post‐emergence and the majority of females can become fertilized on the day that they emerge.     

Sri Lankan passion fruit mottle virus, a potyvirus infecting golden passion fruit in Sri Lanka

A sap-transmissible virus, provisionally named Sri Lankan passion fruit mottle virus (SLPFMV), was isolated from Passiflora edulis f. flavicarpa and shown to induce leaf mottling and distortion in that host. The virus infected 23 species in five plant families with systemic infection being common in the Passifloraceae. Chenopodium amaranticolor was a good local lesion host and Passiflora foetida was a useful systemic host for purification. In P. foetida extracts, SLPFMV lost infectivity after 10 min between 70–75°C, 6–7 days at 20–23°C and at dilutions of 10^--⁵ -W^-6. The virus had flexuous, filamentous particles with a normal length of c. 841 nm. Two polypeptides of mol. wt c. 33 200 and 28 700 were detected in purified virus preparations, and a major species of double-stranded RNA (mol. wt 7.0 × 10⁶), was detected in infected plants. Pinwheels, tubular and laminated inclusions were found in ultrathin sections of infected P. edulis f. plavicurpa and cylindrical inclusions were observed in epidermal strips. SLPFMV was transmitted by the aphids Myzus persicae, Aphis spiraecola, A. gossypü and A. cruccivora after brief acquisition feeds. SLPFMV reacted with antisera to several potyviruses including passion fruit woodiness virus, passion fruit ringspot virus, potato virus Y and watermelon mosaic virus 2 and thus, apparently, is a member of the potyvirus group.     

Bilayer stabilizing peptides and the inhibition of viral infection: antimeasles activity of carbobenzoxy-Ser-Leu-amide

A number of carbobenzoxy-dipeptide-amides raise the bilayer to hexagonal phase transition temperature of dielaidoylphosphatidylethanolamine (stabilizes the bilayer). The potency of the peptides in stabilizing the bilayer phase is Z-Tyr-Leu-NH₂= Z-Gly-Phe-NH₂>Z-Ser-Leu-NH₂>Z-Gly-Leu-NH₂>Z-Gly-Gly-NH₂. A linear correlation was found between the respective HPLC retention time parameterk for the peptide and the slope of the bilayer stabilization curve determined with model membranes by differential scanning calorimetry. One dipeptide, Z-Ser-Leu-NH₂, reduces measles virus cytopathic effect (CPE) in Vero cells. The mechanism by which this peptide reduces the CPE is not known, although some peptides which raise the bilayer to hexagonal phase transition temperature of phospholipids inhibit membrane fusion.Abbreviations Z carbobenzoxy - DEPE dielaidoylphosphatidylethanolamine - DSC differential scanning calorimetry - HPLC high pressure liquid chromatography - CPE cytopathic effect To whom correspondence should be addressed.     

Detection of CaMV gene I and gene VI protein products in vivo using antisera raised to COOH-terminal β-galactosidase fusion proteins

Specific antisera were prepared to the inclusion body protein (gene VI product) and the gene I product of cauliflower mosaic virus (CaMV). Translational fusions between the lacZ gene and gene VI or gene I were constructed by cloning the relevant DNA fragments into the expression vectors pUR290, pUR291 or pUR292. Large amounts of fusion protein were synthesized when the inserted DNA fragment was in frame with the lacZ gene of the expression vector. These fusion proteins were used to raise specific antisera to gene VI and gene I proteins of CaMV. Antiserum to the gene VI product detected a range of proteins in crude extracts and in a subcellular fraction enriched for virus inclusion bodies. This range of proteins was further shown to be related to gene VI by Staphylococcus aureus V8 partial proteolysis. Antiserum to the gene I product detected viral specific proteins of 46, 42 and 38 K in preparations of CaMV replication complexes from infected plants but not in any other subcellular fraction.     

Identification,purification, and characterization of pathogenesis-related proteins from virus-infected Samsun NN tobacco leaves

Ten pH-3 soluble, low-molecular-weight pathogenesis-related proteins (PRs) were found to accumulate in leaves of tobacco cv. Samsun NN reacting hypersensitively to tobacco mosaic virus. Besides the previously characterized PRs 1a, 1b, 1c and 2, these proteins were provisionally designated N, O, P, Q, R, and S in order of decreasing electrophoretic mobility in native polyacrylamide gels. Two-dimensional gel electrophoresis indicated that the PRs consist of single polypeptides, except for R, which is composed of two components with slightly different molecular weights. Estimated molecular weights in SDS-containing gels were: PRs 1a and 1b 17 kD, 1c 16.5 kD, 2 31 kD, N 33 kD, O 35 kD, P 27 kD, Q 28 kD, R 13 and 15 kD, and S 25 kD. However, based on their elution from gel filtration columns and relative moblities in native gels of different acrylamide concentrations, P and Q appeared to have molecular weights similar to those of the PR 1 group. Upon chromatofocusing no additional components were resolved. The PRs were eluted between pH 7 and 4; except for R, their pIs, as judged from isoelectric focusing, appeared to lie in the range from pH 4 to 5.2. In the presence of 6 M urea PR 1a was split into two components, one of which was strongly retarded on gels, as were P and Q. None of the PRs was detected when gels were stained for glycoproteins.By combinations of gel filtration, DEAE-cellulose chromatography, and chromatofocusing, PRs 1a, 1b, 1c, 2 and N were purified, their amino acid compositions determined, and antisera raised against each of these components. By Western blotting, antisera against either PR 1a, 1b, or 1c reacted with each of the components of the PR 1 group, as well as with PR S. Similarly, the antisera against either PR 2 or N reacted with both 2 and N, as well as with O and R. On the basis of major similarities in molecular weight characteristics, amino acid compositions, and serological relationships, it is proposed to classify tobacco PRs into five groups: 1: PRs 1a, 1b, and 1c; 2: 2a (formerly 2), 2b (N), and 2c (O); 3: 3a (P), and 3b (Q); 4: 4a and 4b (the two components of R); and 5: PR 5 (S).     

Reassembly of brome mosaic virus from dissociated virus

The reconstitution of Brome Mosaic Virus (BMV) has been studied using neutron scattering. Experiments were performed on disassembled virus without subsequent separation of components. Phase diagrams of the disassembly and subsequent reassembly of BMV were established as a function of pH and LiCl molarity by analytical centrifugation and quasi-elastic light scattering. Disassembly occurs at a pH above 6.5 and above 0.8 M LiCl. On reassembly, if the pH is lowered first, capsids are formed without subsequent incorporation of RNA. Neutron scattering was used to investigate the formation of virus particles, when the ionic strength was lowered from 1.4 to 0.1 M LiCl at pH 7.8. The reconstitution was followed continuously. As it was driven by a lowering of the ionic strength the kinetics of the process cannot be studied for short times. However the fact that at any given ionic strength no evolution of the scattering was observed with time implies that the reconstitution is complete within a few minutes. The observations in buffers with various amounts of D₂O lead to the conclusion that the reassembly is achieved by co-condensation of the RNA and of the capsid proteins.     

Turnover of Brain Monoamine Oxidase Measured In Vivo by Positron Emission Tomography Using l-[11C]Deprenyl

The distribution of carbon-11-labeled L-deprenyl, an irreversible inhibitor of monoamine oxidase type B (MAO-B), was determined in the baboon brain by positron emission tomography. The irreversible blood-to-brain transfer constant (influx constant, K_i) was measured using a complete metabolite-corrected arterial plasma concentration curve. This influx constant was used as a measure of functional enzyme activity for sequential determinations of MAO-B recovery following a single high dose of unlabeled l -deprenyl. The half-life for turnover of MAO-B was thus determined to be 30 days. Using appropriate irreversible inhibitors, this procedure should be generally useful for determining enzyme turnover rates in any organ in vivo and can be applied to some human studies as well.     

Increased Concentrations of 3-Hydroxykynurenine in Vitamin B6 Deficient Neonatal Rat Brain

Increased concentrations of the endogenous tryptophan metabolite 3-hydroxykynurenine (3-HK) were measured in the brains of vitamin B6 deficient neonatal rats. Mean concentrations of 3-HK in B6 deficient cerebellum, corpus striatum, frontal cortex, and pons/medulla ranged from 9.7 to 18.6 and 102 to 142 nmol/g of wet tissue at 14 and 18 days of age, respectively. 3-HK was not significantly increased in control neonatal or adult rat brain, vitamin B6 deficient rat brain at 7 days of age, or in brains from adult rats deprived of vitamin B6 for 58 days. The administration of daily intraperitoneal injections of vitamin B6 from the 14th to the 18th day of age decreased the concentration of 3-HK to control levels. 3-HK has been shown by other investigators to produce seizures when injected into the cerebral ventricles of adult rodents. Thus, our studies show the accumulation in brain of a putative endogenous convulsant as the result of a nutritional deficiency.     

Characterization ofR. fredii QB1130, a strain effective on commercial soybean cultivars

Summary Two rhizobial strains (QB1130 and C3A) from northeast China were identified asRhizobium fredii on the basis of growth rate, media acidification and growth on a wide range of carbon substrates. The strains were shown to be distinct from USDA 191 on the basis of plasmid number and size. Bothnif and commonnod genes were located on the 295 kb plasmid of strains QB1130 and USDA 191, while onlynif genes were identified on this plasmid in C3A. When used to inoculate four commercial soybean (Glycine max) cultivars, one of the strains (C3A) was found to be ineffective, while the other (QB1130) was at least as effective as USDA 191, a strain ofR. fredii reported to be widely effective on North American cultivars of soybean. Further, QB1130 was capable of more effective nodulation of cowpea or the uncultivated soybean line, Peking, than either USDA 191 or the slow-growingBradyrhizobium japonicum USDA 16. Strain QB1130 should be useful for studies directed at improving symbiotic performance in soybean, or for studies of the comparative physiology and genetics of FG and SG strains on a single host.