Japanese barberry seed predation by Rhagoletis meigenii fruit flies harboring Wolbachia endosymbionts

The phytophagous fruit fly Rhagoletis meigenii harbors the bacterium Wolbachia pipientis and, together with Japanese barberry, form a tri-partite symbiosis. R. meigenii is a seed predator of invasive Japanese barberry plants and is dependent on this insect-plant interaction for reproductive success. The endosymbiotic bacterium W. pipientis is a reproductive parasite known to alter the sex ratios of offspring and the fitness of infected host insects. We investigated Japanese barberry fruit for the degree of infestation by R. meigenii and characterized the Wolbachia strain infecting R. meigenii. Densities of R. meigenii in four naturalized stands of Japanese barberry revealed low numbers of fruit flies with high variability in the population densities observed among individual plants. Overall, R. meigenii infested roughly 10–20 % of the Japanese barberry fruits analyzed; fruit with two seeds (vs. one seed) were the most frequently infested. Approximately, 90 % of the R. meigenii tested positive for Wolbachia infection via PCR amplification of the Wolbachia surface protein (wsp) gene. No bacterial strain diversity was observed when comparing multi-locus sequence typing (MLST) profiles within or among five R. meigenii populations in Maine, although the MLST profile obtained from R. meigenii differed from three co-occurring Rhagoletis. The Wolbachia endosymbiont of R. meigenii is a member of the Wolbachia supergroup A and the ST-13 cluster complex.     

Yohimbine increases plasma insulin concentrations of dogs

Recent evidence suggests that catecholamines inhibit insulin release by stimulating alpha 2-adrenoreceptors in beta-cells of the pancreatic islets. In the present study, iv injections of 0.1 and 0.3 mg/kg of yohimbine, an alpha 2-adrenoreceptor antagonist, resulted in increased plasma insulin and decreased plasma glucose concentrations in the dog. The use of alpha 2-adrenoreceptor antagonists may be of value in non-insulin-dependent diabetic patients by counteracting the inhibitory influence of endogenous catecholamines.     

Evidence for retrograde flow of spermatozoa into the urinary bladder of bulls during electroejaculation

Spermatozoa were not found in the urine collected from 12 bulls before electroejaculation, whereas spermatozoa were found in the urine collected after electroejaculation. The concentration of spermatozoa in four consecutive samples of urine collected during the first postelectroejaculation micturition did not differ (P > 0.80) within bulls, suggesting that the spermatozoa found in the urine were those that had flowed into the urinary bladder during electroejaculation. The mean percentage of retrograde flow was 21% and ranged from 1 to 50% for the 12 bulls. These findings demonstrate that there was a significant urinary loss of spermatozoa during electroejaculation.     

SSCP analysis of the tyrosine kinase domain of the insulin receptor gene: Polymorphisms detected in South African black and white subjects

The frequency of DNA polymorphisms in the tyrosine kinase domain (exons 17–21) of the insulin receptor gene was assessed in 30 black and 30 white South Africans, using single-stranded conformation polymorphism and direct sequencing analysis. A comparison of the frequencies of the normal versus the combined polymorphic alleles, found only in exon 17, showed a significant difference between black and white groups (P = 0.037). Received: 25 May 1995 / Revised: 1 September 1995     

Purification and characterization of tomatinase from Fusarium oxysporum f. sp. lycopersici.

The antifungal compound alpha-tomatine, present in tomato plants, has been reported to provide a preformed chemical barrier against phytopathogenic fungi. Fusarium oxysporum f. sp. lycopersici, a tomato pathogen, produces an extracellular enzyme inducible by alpha-tomatine. This enzyme, known as tomatinase, catalyzes the hydrolysis of alpha-tomatine into its nonfungitoxic forms, tomatidine and beta-lycotetraose. The maximal tomatinase activity in the fungal culture medium was observed after 48 h of incubation of germinated conidia at an alpha-tomatine concentration of 20 micrograms/ml. The enzymatic activity in the supernatant was concentrated against polyethylene glycol 35,000, and the enzyme was then purified to electrophoretic homogeneity by a procedure that includes preparative isoelectric focusing and preparative gel electrophoresis as main steps. The purification procedure had a yield of 18%, and the protein was purified about 40-fold. Tomatinase was found to be a monomer of 50 kDa by both native gel electrophoresis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The analytical isoelectric focusing of the native tomatinase showed at least five isoforms with pIs ranging from 4.8 to 5.8. Treatment with N-glycosidase F gave a single protein band of 45 kDa, indicating that the 50-kDa protein was N glycosylated. Tomatinase activity was optimum at 45 to 50 degrees C and at pH 5.5 to 7. The enzyme was stable at acidic pH and temperatures below 50 degrees C. The enzyme had no apparent requirement for cofactors, although Co2+ and Mn2+ produced a slight stimulating effect on tomatinase activity. Kinetic experiments at 30 degrees C gave a K(m) of 1.1 mM for alpha-tomatine and a Vmax of 118 mumol/min/mg. An activation energy of 88 kJ/mol was calculated.     

QTL analysis of trichome-mediated insect resistance in potato

Genetic mapping of several components of a complex type of insect resistance has been undertaken as a means toward more efficient use of the valuable characteristics of a wild relative of potato. RFLP maps constructed on interspecific diploid progenies of Solanum tuberosum × S. berthaultii were used in conjunction with morphological, biochemical and biological phenotyping to identify quantitative trait loci (QTLs) contributing to trichome-mediated insect resistance. By superimposing QTL data for a wide range of phenotypes including biochemical assays, correlative and direct screens for insect resistance, and adaptation to the target environment on the genetic maps, we have addressed the organization, action and interaction of genes controlling the resistance mechanism. The outcome contributes to an understanding of the association between component traits and between desirable and undesirable features of the donor species generated in an applied breeding program. Research is proceeding toward the development of selectable markers for the introgression and transfer of this resistance among potato gene pools.