Byssochlamys nivea with patulin-producing capability has an isoepoxydon dehydrogenase gene (idh) with sequence homology to Penicillium expansum and P. griseofulvum

Nucleotide sequences of the isoepoxydon dehydrogenase gene (idh) for eight strains of Byssochlamys nivea were determined by constructing GenomeWalker libraries. A striking finding was that all eight strains of B. nivea examined had identical nucleotide sequences, including those of the two introns present. The length of intron 2 was nearly three times the size of introns in strains of Penicillium expansum and P. griseofulvum, but intron 1 was comparable in size to the number of nucleotides present in introns 1 and 2 of P. expansum and P. griseofulvum. A high degree of amino acid homology (88 %) existed for the idh genes of the strains of B. nivea when compared with sequences of P. expansum and P. griseofulvum. There were many nucleotide differences present, but they did not affect the amino acid sequence because they were present in the third position. The identity of the B. nivea isolates was confirmed by sequencing the ITS/partial LSU (28 S) rDNA genes. Four B. nivea strains were analysed for production of patulin, a mycotoxin found primarily in apple juice and other fruit products. The B. nivea strains produced patulin in amounts comparable to P. expansum strains. Interest in the genus Byssochlamys is related to the ability of its ascospores to survive pasteurization and cause spoilage of heat-processed fruit products worldwide.     

Escovopsioides nivea is a non-specific antagonistic symbiont of ant-fungal crops

Fungus-growing attine ants maintain a mutualistic relationship with basidiomycete fungi which they cultivate for food. In addition to the fungal partner, attine ant colonies harbor a myriad of microorganisms, including the genus Escovopsis, fungal parasites of the ant crops. Because Escovopsioides nivea is phylogenetically close to Escovopsis, previous studies assumed it has a negative interaction in the ant-fungus association. Here, we present an extended phylogeny of E. nivea based on new collections from different attine ant genera found in different localities. We also carried out co-culture experiments between E. nivea with different fungal cultivars. Our results suggest E. nivea is a symbiont of attine ant colonies, which inhibits the growth of fungal crops, supporting the hypothesis it is antagonistic to the system. However, the patterns of interaction between E. nivea and fungal crops differ from those shown by Escovopsis, suggesting a different evolution from that of the parasite.     

Population dynamics,age composition and survival of Downsiomyia nivea in relation to transmission of diurnally subperiodic filariasis

Diurnally subperiodic Wuchereria bancrofti (DSPWB) filariasis is transmitted by the Downsiomyia nivea. In India, it is prevalent only in the Nicobar district of Andaman and Nicobar Islands. Knowledge of the population dynamics and bio-ecology of vectors is crucial to develop intervention measures. Entomological studies were performed for 12 months by collecting mosquitoes that landed on human baits for feeding in Teressa Island. Age composition, mosquitoes that had laid eggs at least once, finite rate of natural increase (λ) and vector survival reflecting the population dynamics of Do. nivea in relation to transmission of filariasis were estimated. A total of 3625 Do. nivea were collected. Changes in finite rate of increase (λ > 1) during favorable months indicate an increase in the vector population, suggesting the need for intensified intervention. The proportion of mosquitoes completing more than one gonotrophic cycle was higher in months when λ was 1. Do. nivea abundance and its parous densities varied with seasons. Survival of Do. nivea (indicated by the proportion of parous mosquitoes) was lower in the pre-monsoon season than during the monsoon and post-monsoon seasons. The probability of the daily survival of Do. nivea through one gonotrophic cycle was 0.75, with a declining trend as age increased. The maximum transmission of DSPWB occurred during the pre-monsoon, followed by the late monsoon, post-monsoon and monsoon seasons. Perennial transmission is evident. Therefore intervention measures must be planned throughout the year. Prospects of vector control are limited due to the cryptic breeding and diurnal biting habits. Mass chemotherapy with a single dose of an antifilarial drug is a potential option for control.     

Mutations perturbing petal cell shape and anthocyanin synthesis influence bumblebee perception of Antirrhinum majus flower colour

We wished to understand the effects on pollinator behaviour of single mutations in plant genes controlling flower appearance. To this end, we analysed snapdragon flowers (Antirrhinum majus), including the mixta and nivea mutants, in controlled laboratory conditions using psychophysical tests with bumblebees. The MIXTA locus controls petal epidermal cell shape, and thus the path that incident light takes within the pigment-containing cells. The effect is that mixta mutant flowers are pink in comparison to the wild type purple flowers, and mutants lack the sparkling sheen of wild type flowers that is clearly visible to human observers. Despite their fundamentally different appearance to humans, and even though bees could discriminate the flowers, inexperienced bees exhibited no preference for either type, and the flowers did not differ in their detectability in a Y-maze—either when the flowers appeared in front of a homogeneous or a dappled background. Equally counterintuitive effects were found for the non-pigmented, UV reflecting nivea mutant: even though the overall reflectance intensity and UV signal of nivea flowers is several times that of wild type flowers, their detectability was significantly reduced relative to wild type flowers. In addition, naïve foragers preferred wild type flowers over nivea mutants, even though these generated a stronger signal in all receptor types. Our results show that single mutations affecting flower signal can have profound effects on pollinator behaviour—but not in ways predictable by crude assessments via human perception, nor simple quantification of UV signals. However, current models of bee visual perception predict the observed effects very well.     

Presence of alternating glucosaminoglucan in the sheath of Thiothrix nivea

A sheath-forming sulfa oxidizer, Thiothrix nivea, was mixotrophically cultured in a medium supplemented with acetic acid and sodium disulfide. Its sheath, a microtube-like extracellular supermolecule, was prepared by selectively removing the cells with lysozyme, sodium dodecyl sulfate, and sodium hydroxide. The sheath was not visibly affected by hydrazine treatment, suggesting that it is not a proteinous supermolecule. From the acid hydrolysate of the sheath, glucose and glucosamine were detected in an approximate molar ratio of 1:1. Three other saccharic compounds were detected and recovered by HPLC as fluorescent derivatives prepared by reaction with 4-aminobenzoic acid ethyl ester. Nuclear magnetic resonance (NMR) analysis suggested that one of the derivatives was derived from an unidentified deoxypentose. NMR analysis for the other 2 derivatives showed that they were derived from β-1,4-linked disaccharides and tetrasaccharides, which were composed of glucose and glucosamine. The sheath was readily broken down by weak HCl treatment, releasing an unidentified deoxypentose and polymer. Chemical analysis showed the presence of β-1,4-linked d-Glcp and d-GlcNp in the polymer. NMR analysis revealed that the polymer had a repeating unit of →4)-d-Glcp-(β1→4)-d-GlcNp-(β1→. The solid-state 1D-¹³C NMR spectrum of the polymer in N-acetylated form supported this result. The molecular weight of the polymer was estimated to be 8.2 × 10⁴ by size exclusion chromatography. Based on these results, the sheath of T. nivea is hypothesized to be assembled from alternately β-1,4-linked glucosaminoglucan grafted with unidentified deoxypentose.     

Association of three highly mutable genes involving pigmentation in Anthirrhinum majus

Unstable alleles at three unlinked loci (delilah, nivea and pallida) can mutate somatically to allow the production of clones of pigmented cells (“flakes”) in particular parts of the corolla. The size of the flakes depends on the timing of the mutations during the development of the flower.     

Ambrosia johnstoniorum (Asteraceae), a new species of ragweed from the Chihuahuan Desert

Ambrosia johnstoniorum is described from two collections of I. M. Johnston from central Coahuila. The taxon has a distinctive assortment of characteristics and appears most closely related toAmbrosia nivea (Robins. & Fern.) Payne of northern Chihuahua.     

Antibiose manifestée par une souche de Byssochlamys nivea Westling, 1909. II. Spectre d'activité

A strain of Byssochlamys nivea, isolated from altered heat processed strawberries, produces an antibiotic substance which is efficient against several species of gram (-) bacteria and a few species of gram (+). This substance is completely ineffectual on Mycobacteria and fungi (yeasts or moulds) at the concentration used.     

Feeding habits and dietary overlap of Naididae (Oligochaeta) from a bog stream

Feeding habits and dietary overlap of three species of naidid oligochaetes (Chaetogaster diastrophus, Dero digitata, Dero nivea) were studied during June 1982–December 1983 from a bog stream in Wisconsin, USA. Chaetogaster diastrophus primarily ingested diatoms, while D. digitata and D. nivea primarily ingested detritus. Dietary overlap was substantial (97–98%) between D. digitata and D. nivea using the dietary overlap coefficient. Dietary overlap between C. diastrophus and D. digitata was 58–62% and that between C. diastrophus and D. nivea was 51–55%. Dietary differences existed between the three species in the percentage of each major food type and diatom genera ingested, selective ingestion or avoidance of diatom genera and in the size classes (length and/or volume) of diatoms consumed. These data suggest temporal coexistence of these species may possibly be due to complex food resource partitioning, although in this habitat, C. diastrophus, D. digitata, and D. nivea did not exhibit concurrent peak abundances; thus, interspecific competition for food was minimized.     

STUDIES ON THE PRODUCTION AND PHYSIOLOGICAL EFFECTS OF ASYMMETRIN

In shake-flask culture asymmetrin was produced by PenicIlliumthomiiaud Byssochlamys niveaduring autolysis. A bioassay wasdevised to estimate relative concentrations of this compound.Culture filtrates of P. thomiicontaining asymmetrin caused adecrease in wet weight, dry weight, and total nitrogen of Phaseolusvulgarisup to 18 days after treatment. At certain intervalsafter treatment with culture filtrate of B. nivea,respirationwas inhibited, and changes were observed in isotope ratio valuesof plants supplied with glucose-¹⁴ C. Plants treated previouslywith culture filtrates of B. nivearesponded but little to gibberelhcacid. High concentrations of mdoleacetic acid inhibited growthof control plants but stimulated growth of plants treated withculture filtrate of B. nivea. ¹Present address: United Fruit Company, Norwood, Massachusetts.Supported in part by a Public Health Service Fellowship No.GF 13,776 from the division of General Medical Sciences, PublicHealth Service, National Institutes of Health, and Grant G 20989from the National Science Foundation. ²Journal Paper No. 2170 of the Purdue Agricultural ExperimentStation.     

De novo activation of the transposable element Tam2 of Antirrhinum majus

Summary The nivea locus of Antirrhinum majus encodes the enzyme chalcone synthase required for the synthesis of red anthocyanin pigment. The stable allele niv-44 contains an insertion in the nivea gene (Tam2) which has all the structural features of a transposable element. We have shown that this insertion can excise from the nivea locus when niv-44 is combined with another allele (niv-99) in a heterozygote. Activation of Tam2 excision is caused by a factor tightly linked to the niv-99 allele and may be due to complementation between Tam2 and a related element, Tam1. Factors which repress the excision of Tam2 and Tam1 are also described. Repression is not inherited in a simple mendelian way. Many stable mutations may be due to the insertion of transposable elements. Our data suggest that their stability may be due to the absence in the genome of activating factors and to the presence of repressors.     

Dry soil determines the pseudoviviparous reproduction in Comanthera nivea (Eriocaulaceae) in the Campos Rupestres in south-eastern Brazil

Pseudovivipary is an asexual reproduction strategy correlated with extreme environments. Comanthera nivea occurs in habitats with low water retention. This study investigated the effect of soil moisture availability on C. nivea pseudoviviparous reproduction and flowering. We established four permanent plots (1 × 1 m), two in a shaded area, in which we marked 15 rosettes in each plot, and two in a full-sun area, in which we marked 10 rosettes in each plot. We made monthly observations from August 2016 to January 2017, to quantify the number of flower heads and of pseudoviviparous ramets per rosette, and measured soil moisture. Our results showed a high correlation between soil moisture and flowering. Flowering in C. nivea occurs in periods of increased soil moisture, whereas pseudoviviparous reproduction occurs in the driest period. The advantages of a pseudoviviparous canopy-forming strategy in habitats with scarcity of water in the soil are discussed.     

New species of Peliosanthes,Rohdea and Tupistra (Asparagaceae) from Laos and Vietnam

We describe and illustrate four new species, Peliosanthes choriandra, P. tatianae and Tupistra orlovii from central to northern Laos, and Rohdea filosa from northern Vietnam. These are all very local in distribution and endemic to the respective countries. We also report new localities and their ecological conditions for five other species of Peliosanthes (P. argenteostriata, P. hirsuta, P. irinae, P. micrantha and P. nivea) recently described from Laos and/or Vietnam. Furthermore, Peliosanthes nivea is recorded as new to the flora of Laos.     

Immobilized copies with a nearly intact structure of the transposon Tam3 in Antirrhinum majus: implications for the cis-element related to the transposition

 In this study we have focused on two copies of the transposon Tam3 isolated from an Antirrhinum majus plant which has flower variegation due to the excision of Tam3 from the nivea locus. These two copies possess a high homology, over 95%, to an active Tam3 element found in the nivea ^{recurrence:Tam3} allele. Although somatic excision of the Tam3 copy from the nivea locus can be detected at 15°C by Southern blotting, neither of the two copies showed any sign of the excision. Both of the immobilized copies were also found in five varieties from different A. majus sources, all of which contain common fragments. The results suggest that the two copies have been fixed in the genomes of many A. majus varieties. Structural differences between these immobilized copies and the known active copy were mainly observed in the subterminal regions, including the terminal inverted repeats. The immobility of the two Tam3 copies might be due to mutations within the end regions of essential cis-elements in Tam3 transposition, as reported for Ac and En/Spm. Received: 30 June 1997 / Accepted: 5 August 1997     

The transposable element Tam1 of Antirrhinum majus is 17 kb long

Summary The nivea locus of Antirrhinum majus encodes chalcone synthase, a key enzyme in anthocyanin biosynthesis. Genetic instability is known to occur at this locus. In vitro cloning and characterization of genomic DNA fragments from the unstable nivea-recurrens allele T53 revealed that the instability of nivea-recurrens is due to the presence of a 17 kb DNA insert in the nivea locus. Somatic instability leading to the variegated phenotype, i.e. highly spotted flowers, is due to frequent excision of the 17 kb Tam1 element (Transposon antirrhinum majus) during development of the plant. Excision of Tam1 is not tissue specific, but occurs with similar frequencies in leaves and blossoms.     

The ultrastructure of the diffuse kinetochore in Luzula nivea

Material of Luzula nivea was fixed and processed in the normal way for sectioning and use of the transmission electron microscope. In addition, irradiated as well as control material was employed. Irradiation is known to produce chromosome breaks which rejoin. Apparent side-by-side adherence at metaphase of the chromosomes of Luzula nivea in control material disappeared at the earliest moment of anaphase and because of the high visibility of the kinetochores of this species, one pair of sister kinetochores could be readily associated with one pair of chromatids. Rejoining of chromosome breaks which does not disappear at anaphase, could not be distinguished at metaphase from the above described adherence. Chromatids also were apparently adherent at metaphase and it is pointed out that this is commonly seen in most organisms sectioned for the electron microscope. The apparent adherence is regarded as an artifact of fixation and subsequent processing. The authors do not agree with the interpretation of the chromosomes of Luzula as polycentric. From serial sections it has been established that in Luzula nivea a single diffuse kinetochore extends along most of the length of the chromosome, but does not occupy the whole width.     

Comparison of fungicidal properties of non-thermal plasma produced by corona discharge and dielectric barrier discharge

The inactivation of four micromycete species by action of non-thermal plasma was followed. Two sources of plasma were compared, namely, positive corona discharge and dielectric barrier discharge. The corona discharge appeared as suitable for fungal spore inactivation in water suspension, whereas the barrier discharge inactivated spores on the surface of cultivation agar. Cladosporium sphaerospermum was the most sensitive, being inactivated within 10 min of exposure to plasma, whereas Aspergillus oryzae displayed decrease in viable cell count only, the complete inactivation was not achieved even after 40 min of exposure. Intermediate sensitivity was found for Alternaria sp. and Byssochlamys nivea. The significant delay of growth was observed for all fungi after exposure to sublethal dose of plasma, but we failed to express this effect quantitatively.