Genetic structure of natural populations ofDryas iulia (Lepidoptera: Nymphalidae) revealed by enzyme polymorphism and mitochondrial DNA (mtDNA) restriction fragment length polymorphism (RFLP)

Dryas iulia appears to have undergone a mode of evolution different from that of other members of its subfamily (Heliconiinae). While other species constitute highly subdivided and inbred populations, those ofD. iulia are thought to be large and uniform. Analyzing six samples from Southern Brazil (state of Rio Grande do Sul) in relation to three enzyme systems (EST, LAP, and PGM) and their mtDNA RFLP patterns, we found that they are very similar at the molecular level. TheF statistics for enzyme polymorphism data revealed that inbreeding makes a great contribution to the population homozygosity, sinceF _IS equals 0.1322 andF _ST equals 0.0023. Since the chi-square test showed thatF _ST is not significant, we conclude that all localities belong to the same population. The mtDNA differentiation was about 12 times greater than for nuclear genes;F _ST was equivalent to 0.0265. We suggest that this difference is due to a higher dispersal of males, in relation to females.     

Chromosomal localization of four human zinc finger cDNAs

cDNA clones encoding zinc finger motifs were isolated by screening human placenta and T-cell (Peer) cDNA libraries with zinc finger (ZNF) consensus sequences. Unique cDNA clones were mapped in the human genome by rodent-human somatic cell hybrid analysis and in some cases in situ chromosomal hybridization. ZNF 80 mapped to 3p12-3qter, ZNF 7 was previously mapped to 8q24 and is here shown by in situ hybridization and use of appropriate hybrids to map telomeric to the MYC locus. ZNF 79 mapped to 9q34 centromeric to the ABL gene and between a constitutional chromosomal translocation on the centromeric side and the CML specific ABL translocation on the telomeric side. ZNF77 mapped to 19p while ZNF 78L1 (pT3) mapped to 19q. Chromosome 19 carries many ZNF loci and other genes with zinc finger encoding motifs; the pT3 clone additionally detected a locus designated ZNF 78L2, which mapped to chromosome region 1p, most likely in the region 1p32 where the MYCL and JUN loci map.     

Metabarcoding reveals seasonal and spatial patterns of arthropod community assemblages in two contrasting habitats: Desert and oasis of the Baja California Peninsula,Mexico

Aim

Desert springs or oases are the only permanent mesic environments in highly water-limited arid regions. Oases have immense cultural, evolutionary and ecological importance for people and a high number of endemic and relic species. Nevertheless, they are also highly vulnerable ecosystems, with invasive species, overexploitation and climate change being the primary threats. We used the arthropod communities' spatiotemporal diversity and distribution patterns as a proxy to understand biodiversity dynamics in two geographically close but ecologically contrasting and highly threatened ecosystems: deserts and oases.

Location

Baja California Peninsula, Mexico.

Methods

Arthropod communities at five oases and surrounding desert scrub areas were sampled in two seasons. Using DNA metabarcoding and traditional taxonomic surveys, we tried to identify what biotic and abiotic characteristics of the habitat are important drivers of arthropod diversity and how these characteristics can change across spatial and temporal scales.

Results

Over 6200 individuals representing 23 orders were collected. In oasis samples, the community composition fluctuated more in space (i.e. among sites) than in time (i.e. seasons). Thus, seasonal changes did not affect oasis community diversity and composition, but the dissimilarity among sites increased with geographic distance. Moreover, anthropic activities negatively correlated with arthropod diversity in oases. On the other hand, the season, geography (e.g. latitude) and biotic characteristics of the habitat (e.g. sampled scrub species) significantly affected the diversity and composition of the desert arthropod communities.

Main Conclusions

Neutral dynamics (e.g. historical climatic events, dispersal limitation and spatial component) and human impact significantly influenced the biodiversity patterns of each oasis. In contrast, the habitat's seasonal variation and biotic characteristics were the most important variables influencing the diversity of the desert communities. Baja California oases harbour distinct invertebrate communities; therefore, each oasis should be conserved individually to preserve these unique assemblages.     

Canopy tree mortality depends on the proportion of crown exposed to sunlight,but this effect varies with species' wood density

Understanding what drives changes in tree mortality as well as the covariates influencing trees' response is a research priority to predict forest responses to global change. Here, we combined drone photogrammetry and ground-based data to assess the influence of crown exposure to light (relative to total crown area), growth deviations (relative to conspecifics), tree size, and species' wood density (as a surrogate for light-demanding and shade-tolerant life-history strategies) on the mortality of 984 canopy trees in an Amazon terra firme forest. Trees with lower wood density were less prone to die when their proportion of crown was more exposed to sunlight, but this relationship with relative crown exposure weakened and slightly reversed as wood density increased. Trees growing less than their species average had higher mortality, especially when the species' wood density decreased. The role of wood density in determining the survival of canopy trees under varying light conditions indicates differential responses of light-demanding versus shade-tolerant species. Our results highlight the importance of accounting for life-history strategies, via plant functional types, in vegetation dynamic models aiming to predict forest demography under a rapidly changing climate. Abstract in Spanish is available with online material.     

Novel Miscanthus hybrids: Modelling productivity on marginal land in Europe using dynamics of canopy development determined by light interception

New biomass crop hybrids for bioeconomic expansion require yield projections to determine their potential for strategic land use planning in the face of global challenges. Our biomass growth simulation incorporates radiation interception and conversion efficiency. Models often use leaf area to predict interception which is demanding to determine accurately, so instead we use low-cost rapid light interception measurements using a simple laboratory-made line ceptometer and relate the dynamics of canopy closure to thermal time, and to measurements of biomass. We apply the model to project the European biomass potentials of new market-ready hybrids for 2020–2030. Field measurements are easier to collect, the calibration is seasonally dynamic and reduces influence of weather variation between field sites. The model obtained is conservative, being calibrated by crops of varying establishment and varying maturity on less productive (marginal) land. This results in conservative projections of miscanthus hybrids for 2020–2030 based on 10% land use conversion of the least (productive) grassland and arable for farm diversification, which show a European potential of 80.7–89.7 Mt year⁻¹ biomass, with potential for 1.2–1.3 EJ year⁻¹ energy and 36.3–40.3 Mt year⁻¹ carbon capture, with seeded Miscanthus sacchariflorus × sinensis displaying highest yield potential. Simulated biomass projections must be viewed in light of the field measurements on less productive land with high soil water deficits. We are attempting to model the results from an ambitious and novel project combining new hybrids across Europe with agronomy which has not been perfected on less productive sites. Nevertheless, at the time of energy sourcing issues, seed-propagated miscanthus hybrids for the upscaled provision of bioenergy offer an alternative source of renewable energy. If European countries provide incentives for growers to invest, seeded hybrids can improve product availability and biomass yields over the current commercial miscanthus variety.     

Two independent type III secretion mechanisms for YopE in Yersinia enterocolitica

Pathogenic Yersinia species escape the infected host's defense mechanisms by targeting cytotoxic Yop proteins into the cytoplasm of macrophages via a type III secretion pathway. Two separate secretion signals contained in YopE were identified, each of which were sufficient but not necessary for the secretion of reporter molecules. One signal is located within the coding sequence of the first 15 amino acids and is sufficient for the secretion of fusion proteins but not required for YopE secretion. The second signal is located downstream at residues 15–100 of YopE and is only recognized by the type III machinery when it is bound to SycE. We propose the existence of two independent mechanisms that allow for the secretion of Yop proteins.     

Regulation of O-antigen chain length is required for Shigella flexneri virulence

It is shown that Shigella flexneri maintains genetic control over the modal chain length of the O-antigen polysaccharide chains of its lipopolysaccharide (LPS) molecules because such a distribution is required for virulence. The effect of altering O-antigen chain length on S. flexneri virulence was investigated by inserting a kanamycin (Km)-resistance cassette into the rol gene (controlling the modal O-antigen chain length distribution), and into the rfbD gene, whose product is needed for synthesis of dTDP-rhamnose (the precursor of rhamnose in the O-antigen). The mutations had the expected effect on LPS structure. The rol ::Km mutation was impaired in the ability to elicit keratoconjunctivitis, as determined by the Serény test. The rol ::Km and rfbD ::Km mutations prevented plaque formation on HeLa cells, but neither mutation affected the ability of S. flexneri to invade and replicate in HeLa cells. Microscopy of bacteria-infected HeLa cells stained with fluorescein isothiocyanate (FITC)-phalloidin demonstrated that both the rol ::Km and rfbD ::Km mutants were defective in F-actin tail formation: the latter mutant showed distorted F-actin tails. Plasma-membrane protrusions were occasionally observed. Investigation of the location of IcsA (required for F-actin tail formation) on the cell surface by immunofluorescence and immunogold electron microscopy showed that while most rol mutant bacteria produced little or no cell-surface IcsA, 10% resembled the parental bacterial cell (which had IcsA at one cell pole; the rfbD mutant had IcsA located over its entire cell surface although it was more concentrated at one end of the cell). That the O-antigen chains of the rol ::Km mutant did not mask the IcsA protein was demonstrated by using the endorhamnosidase activity of Sf6c phage to digest the O-antigen chains, and comparing untreated and Sf6c-treated cells by immunofluorescence with anti-IcsA serum.     

Production of neosolaniol byFusarium tumidum

Extracts from autoclaved maize culture ofFusarium tumidum strain R-5823 were toxic towardsArtemia salina. Bioassay-guided fractionation of the organic extract led to the isolation of the toxic compound that was identified as the trichothecene toxin neosolaniol (NEOS) by¹H,¹³C nuclear magnetic resonance spectroscopy and low-resolution electronic impact mass spectrometry. The amount of NEOS produced by the strain R-5823 was 300 mg/kg maize culture. NEOS was also detected by HPLC in cultures of four out of seven additional strains ofF. tumidum andGibberella tumida with different origin, in amounts ranging from 1 to 311 mg/kg. This is the first report on the production of a trichothecene toxin byF. tumidum.     

Partial deletion of 4p16 band in a ring chromosome and wolf syndrome

Summary A new case of ring chromosome 4 in a 2-day-old female child with multiple malformations is described. By means of the GTG-banding technique, a karyotype 46,XX,r(4), (p16q35) was determined. The characteristics of the child's karyotype and the relationship with the structure of the chromosome, especially the location of the deletion that produces the syndrome, are compared with previous reports.