Variation in regulation of aflatoxin biosynthesis among isolates ofAspergillus flavus

Two new phenotypes ofAspergillus flavus which exhibit novel patterns of aflatoxin production have been identified and characterized. In one of the new variants ofA. flavus, aflatoxin is made in the absence of carbohydrate and concomitantly with growth, without a lag period. A second variant did not produce aflatoxin in the presence or absence of carbohydrate. Chemical mutagenesis of this nonaflatoxigenic strain resulted in mutant strains which produced aflatoxin on carbohydrate-containing media. The aflatoxin production pattern observed in these mutants resembled the typical production scheme, with a lag period through log phase growth.     

Intracolonial worker relationship and sperm competition in the honeybee (Apis mellifera L.)

Summary Queens, homozygous for three marker genes, were inseminated with eight different types of semen, each carrying one combination of the markers. Intracolonial worker relationship (_c) was estimated by genotype frequencies in the offspring of the experimental queens. _c was larger than under random distribution of semen types in the spermatheca. Estimates of most quantitative genetical parameters will be more accurate using the presented estimator for intracolonial relationship. The insemination order affected genotype frequencies in the offspring, suggesting a weak last male advantage. There was, however, no evidence of intra spermathecal sperm competition.     

Reproductive competition and colony fragmentation in the guest-ant,Formicoxenus provancheri

Aggressive reproductive conflicts and dominance interactions among queens are involved in establishing functional monogyny in the ant,Formicoxenus provancheri. Competition among potential reproductives may lead to the founding of new societies by budding or colony fragmentation.     

Secreted oleanolic acid on the cuticleOlea europaea (Oleaceae); a chemical barrier to fungal attack

Summary The leaf of the bitter oliveOlea europaea (Oleaceae) is heavily coated by almost pure oleanolic acid, which forms part of a multichemical defense against fungal attack.We thank Mr K. A. Hoelmer for taking the electron micrographs and also Professor T. Kamikawa for NMR measurements.     

Pheromone behavioral responses in unusual male European corn borer hybrid progeny not correlated to electrophysiological phenotypes of their pheromone-specific antennal neurons

In genetic studies on the sex pheromone communication system of two races of European corn borer, which use opposite pheromone blends of the E and Z compounds, it was found that antennal olfactory cell response amplitudes to the two compounds were controlled by an autosomal factor, whereas behavioral responses to the blends were controlled by a sex-linked locus. Because of the difference in genetic controls, it was postulated that some unusual males would be produced in F₂ crosses between these two races. These unusual males would have antennal olfactory cells that respond as the Z-race males, but would respond behaviorally to the E blend. The present studies combined behavioral studies in a flight tunnel and single cell electrophysiological studies to show that these unusual males do indeed exist. These findings show that the spike amplitude of peripheral olfactory cells is not important in regulating species- or race-specific pheromone responses, as compared to some central nervous system factor assesses the spike frequencies from different pheromone-component-specific cells on the antenna. This factor seems to be essential in governing the pheromone-blend specific behavioral responses of male moths.     

Genetics of toxin production and resistance in phytopathogenic bacteria

Genes for phytotoxin production have been identified and cloned from several phytopathogenic pseudomonads. These genes comprise physically linked clusters that have been located both on the chromosome and on endogenous plasmids. Contained within these genetic regions are resistance genes specific to those toxins that have a bactericidal component to their activity. DNA sequences required for toxin production are often conserved among bacteria with divergent host specificities, suggesting the ability of toxin genes to be transferred between bacteria. Toxins are usually modulators of plant pathogenicity, their production causing a significant increase in disease severity. In one case, however, toxin production appears to be a major contributor to the basic pathogenicity of a plant pathogenic bacterium.     

Unique sex chromosome mediated behavioral response specificity of hybrid male European corn borer moths

Unlike the narrow response windows exhibited by the parent races, hybrid male European corn borers resulting from crosses of the E and Z races respond to a wide range of sex pheromone blends. The F₁ response profile consists of some individuals that respond to both the Z pheromone and the 6535 E/Z blend produced by F₁ females. Some F₁ males fail to respond to any blend and some do not respond as broadly as others. The hybrid male populations, however, are not tuned optimally to the pheromone blend produced by F₁ females and there is no coupling of F₁ blend production and response.     

Effects of a juvenile hormone mimetic,fenoxycarb, on post-embryonic development of the European corn borer,Ostrinia nubilalis Hbn.

Summary The effect of a juvenile hormone mimetic, fenoxycarb, Ro 13-5223, was tested on the larval instars of the European corn borer,Ostrinia nubilalis, by dipping or topical application. When larvae were treated in instars 2, 3 or 4, the duration of the fifth instar was modified. More permanent and fewer supernumerary larvae were obtained when treatment occurred in the early instars. This non-neurotoxic compound exhibited a strong dose-dependent juvenile hormone type of activity when it was applied to last instar larvae. Fenoxycarb prevented the onset of pupation and produced supernumerary larvae and intermediates. Permanent larvae were obtained if fenoxycarb was applied on day 0 or day 1 of the last instar. The use of such a JH mimetic in the understanding of endocrine control of diapause is discussed.     

Effects of feeding on healthy and diseased corn plants on a vector and on a non-vector insect

Insect-transmitted plant pathogens can have positive, negative or no effects on the vector insect. Effects could be direct (caused by the pathogen) or indirect (mediated by changes in the plant). Pathogen effects on non-vector insects are less well known.Peregrinus maidis (Ashmead) (Homoptera: Delphacidae), an insect that is not a vector of the corn stunt spiroplasma (CSS), weighed less 15 days after feeding on CSS-infected corn plants relative to insects feeding on healthy corn plants. Fecundity of non-vector insects that were removed from diseased plants was higher than for insects coming from healthy plants. ForDalbulus maidis (DeLong & Wolcott) (Homoptera: Cicadellidae), an insect that transmits CSS, there were no differences in weight, longevity, eggs per day, weekly or total fecundity after feeding on healthy or on CSS-infected corn plants. Significant differences in some phloem amino acids were detected between healthy and CSS-infected plants. Infected plants also showed an increased phloem acidity as disease symptoms progressed. Feeding on CSS-infected corn plants by an insect that does not vector the pathogen infecting the plant can have favorable consequences as evidenced by an increased fecundity.Scientific aritcle no. 8819, contribution no. A-6605 of the Maryland Agricultural Experiment Station.     

Alternariol,a dibenzopyrone mycotoxin ofAlternaria spp., is a new photosensitizing and DNA cross-linking agent

Summary The mycotoxin alternariol (3,4,5-trihydroxy-6-methyldibenzo [a] pyrone) but not alternariol monomethyl ether (3,4-dihydroxy-5-methoxy-6-methyldibenzo [a] pyrone) is phototoxic toEscherichia coli in the presence of near UV light (320–400 nm). The phototoxicity bioassays with a DNA repair-deficient mutant ofE. coli suggested that DNA may be the molecular target for photo-induced toxicity of alternariol. Interactions between alternariol and double-stranded, supercoiled DNA suggest that alternariol interacts with DNA by intercalation. No DNA breakage was detected in this system; however, alternariol forms a complex and cross-links double-stranded DNA in near UV light. These results suggest that alternariol is a new phototoxic, DNA-intercalating agent and is a DNA cross-linking mycotoxin in near UV light.Acknowledgment. Dr Albert Stoessl (Agriculture Canada, London, Ontario, Canada) generously provided a mixture of alternariol and alternariol monomethyl ether, and made many helpful suggestions. Dr Ashwood-Smith (University of Victoria, Victoria, British Columbia, Canada) kindly supplied the microorganisms through Dr G.H.N. Towers (University of British Columbia, Vancouver). We gratefully acknowledge the gifts. It is a pleasure to acknowledge the able assistance of Mr S. Tallevi.     

Enhanced production of aggregation pheromones in four stored-product coleopterans feeding on methoprene-treated oats

Summary Production of aggregation pheromones by maleOryzaephilus surinamensis, O. mercator, Cryptolestes ferrugineus, andTribolium castaneum was enhanced by feeding on methoprene-treated oats, implicating juvenile hormone in control of pheromone production. Methoprene application to control insects in stored food products may cause enhanced pheromone production by these insects, thus drawing additional beetles into the treated product.Acknowledgments. We thank Dr. G. B. Staal of Zoëcon Corp. for a generous gift of methoprene. Particular thanks are due to J. Dodic for technical assistance. Research funded by the Natural Sciences and Engineering Research Council of Canada and the Science Council of British Columbia.     

Role of toxins in evolution and ecology of plant pathogenic fungi

Many fungal pathogens of plants adapt readily to changes in agriculture. Among the most revealing is a fungal group whose species produce host-selective toxins as key determinants of disease. Several lines of evidence support the hypothesis that these fungi evolved from opportunistic, low-grade pathogens by gaining new genetic information leading to toxin production; in some species, toxin production is known to be under single gene control. as a result of this evolution, these fungi became virulent and host-specialized. The best-known model cases belong to the generaCochliobolus andAlternaria; there are suggestions of evolutionary lines among these genera, with species that range from saprophytes to opportunists to specialized pathogens. Host specialization can lead to genetic isolation, a first step in speciation. Ability to produce host-selective toxin has allowed these fungi to exploit the monocultures and genetic uniformity of modern agriculture. Destructive epidemics have been the result.     

Sclerotial and low aflatoxigenic morphological variants from haploid and diploidAspergillus parasiticus

Summary Serial transfer of mycelial macerates of a wild type, haploid, aflatoxigenic strain ofAspergillus parasiticus in a defined liquid medium resulted in the production of three new morphological classes: a sclerotial form with high aflatoxin production, and two variant forms (fan andfluff) with lowered sporulation, no sclerotia, and attenuated levels of aflatoxin. A genetically marked diploid containing mutant markers for aflatoxin pathway intermediates yielded the same three morphological classes upon serial transfer of macerated mycelia. When these diploid variants were treated with a haploidization agent, and the phenotypes of the resultant segregants scored, a low frequency of colonies producing aflatoxin pathway intermediates was recovered. These genetic data indicate that the structural genes for the aflatoxin pathway are present but somehow attenuated in thefan andfluff strains.This work was supported by a Cooperative Agreement from the U.S. Department of Agriculture, (58-7B30-3-556).     

Insect tissues,not microorganisms,produce linoleic acid in the house cricket and the American cockroach

Summary Biosynthesis of linoleic acid, 182(n–6), was unambiguously demonstrated to occur in the cockroach,Periplaneta americana, and the cricket,Acheta domesticus. Axenic tissue from both of these insect species was demonstrated by radio-gas-liquid chromatography (radio-GLC) and radio-high-performance liquid chromatography (radio-HPLC) to incorporate [1-¹⁴C]acetate and [1-¹⁴C]oleate into this essential fatty acid.This work was supported by the National Science Foundation under grant DCB-8914417. We would like to thank Coby Schal for his generous gift of American cockroaches and Tania Kellermeyer for her excellent technical assistance.     

Stimulatory effect of methyl jasmonate on the ethylene production in tomato fruits

Summary Methyl jasmonate at a concentration of 0.5% in lanolin paste was applied to detached mature green and red ripe tomatoes cv. Tempo. One to 10 days after treatment, slices were cut at a depth of about 2 mm for ethylene determination. It was found that methyl jasmonate strongly stimulated ethylene production both in green and red fruits, production was about 1.6 to 7.9 times higher than in control tissue.Acknowledgments. We wish to thank Dr E. Demole, Firmenich SA, Geneva, Switzerland, for the gift of authentic (±)-methyl jasmonate and Mrs H. Sas for her excellent technical assistance.     

Hydroxylation of menthols and cineoles withm-chloroperbenzoic acid

Summary Reaction of menthols and cineoles withm-chloroperbenzoic acid afforded tertiary, secondary, and primary alcohols, some of which were natural products having potent plant growth regulatory activity or were mammlianm metabolies.We thank Nippon Terpene Co. Ltd for their generous gift of the compounds used in this work and Drs M. Kido and Y. Fukuyama, Otsuka Pharmaceutical Co. Ltd, for measurement of high resolution mass spectra. The present work was supported in part by a Grant-in-Aid for Cancer Research from the Ministry of Health and Welfare.     

Laccase production byPolyporus sanguineus under different nutritional and environmental conditions

Summary Laccase production was higher in malt extract medium than in lignin, andPolyporus sanguineus appears to be better thanPolyporus versicolor andTrametes hirsuta (syn.Polyporus hirsutus) for enzyme production. Phenolic compounds, of which resorcinol was the most active, induced enzyme production; while sugars repressed it. A temperature of 37°C, pH 3 and indulin AT at a concentration of 0.2% gave the best enzyme yield.A part of Ph. D. thesis of D.S. Arora.Acknowledgments. We thank Westvaco Chemical Division, USA, and Dr P.S. Rehill, Forest Research Institute, Dehradun, India for providing lignin samples and the fungal strain, respectively. D.S. Arora further thanks University Grants Commission, New Delhi for financial assistance.     

Paracelsin; characterization by NMR spectroscopy and circular dichroism,and hemolytic properties of a peptaibol antibiotic from the cellulolytically active mnoldTrichoderma reesei. Part B

Summary Paracelsin, a hemolytic and membrane active polypeptide antibiotic of the peptaibol class which is excreted by the moldTrichderma reesei, was obtained by a simplified and isolation procedure utilziing hydrophobic adsorber resin. Investigation by¹³C nuclear magnetic resonance spectroscopy and circular dichroism revealed considerable helical portions in solution, and the very recently accomplished sequence determination of paracelsin allows the discussion of the results with regard to the closely related analogues, alamethicin and suzukacillin. A selective cleavage of the peptide was achieved by careful treatment with various acids, and a buffer of pH 8.25 and of high ionic strength made possible the quantitative determination of the C-terminal phenylalaninol released by means of ion-exchange chromatography. The significance of the production of paracelsin and related mycotoxins of the peptaibol class, exhibiting various kinds of biological activity, is discussed with respect to the extensive effort being made towards biotechnological applications of species, strains and cellulolytically highly active mutants of the fungusTrichoderma.Presented in part at the 5th European Symposium on Animal, Plant and Microbial Toxins, Hannover, August 29–September 2, 1983 and a lecture given at Ciby-Geigy/Basel in March 1984.Acknowledgment. We thank I. Ackermann for excellent and skilled technical assistance and gratefully acknowledge the help of R. Ratz for support in CD spectroscopy.     

Babesia bovis: the effect of acute inflammation and isoantibody production in the detection of babesial antigens

Summary Immunoblots ofBabesia bovis antigen contain dominant antigens which react not only with antisera toB. bovis but with sera from naive calves recovering from an acute inflammatory reaction. It seems likely these antigens are from the host rather than the parasite.