Exploring Regional Variation in Roost Selection by Bats: Evidence from a Meta-Analysis

Background and Aims

Tree diameter, tree height and canopy closure have been described by previous meta-analyses as being important characteristics in roost selection by cavity-roosting bats. However, size and direction of effects for these characteristics varied greatly among studies, also referred to as heterogeneity. Potential sources of heterogeneity have not been investigated in previous meta-analyses, which are explored by correlating additional covariates (moderator variables). We tested whether effect sizes from 34 studies were consistent enough to reject the null hypothesis that trees selected by bats did not significantly differ in their characteristics from randomly selected trees. We also examined whether heterogeneity in tree diameter effect sizes was correlated to moderator variables such as sex, bat species, habitat type, elevation and mean summer temperature.

Methods

We used Hedges’ g standardized mean difference as the effect size for the most common characteristics that were encountered in the literature. We estimated heterogeneity indices, potential publication bias, and spatial autocorrelation of our meta-data. We relied upon meta-regression and multi-model inference approaches to evaluate the effects of moderator variables on heterogeneity in tree diameter effect sizes.

Results

Tree diameter, tree height, snag density, elevation, and canopy closure were significant characteristics of roost selection by cavity-roosting bats. Size and direction of effects varied greatly among studies with respect to distance to water, tree density, slope, and bark remaining on trunks. Inclusion of mean summer temperature and sex in meta-regressions further explained heterogeneity in tree diameter effect sizes.

Conclusions

Regional differences in roost selection for tree diameter were related to mean summer temperature. Large diameter trees play a central role in roost selection by bats, especially in colder regions, where they are likely to provide a warm and stable microclimate for reproductive females. Records of summer temperature fluctuations inside and outside tree cavities that are used by bats should be included in future research.     

Host‐induced gene silencing of an essential chitin synthase gene confers durable resistance to Fusarium head blight and seedling blight in wheat

Fusarium head blight (FHB) and Fusarium seedling blight (FSB) of wheat, caused by Fusarium pathogens, are devastating diseases worldwide. We report the expression of RNA interference (RNAi) sequences derived from an essential Fusarium graminearum (Fg) virulence gene, chitin synthase (Chs) 3b, as a method to enhance resistance of wheat plants to fungal pathogens. Deletion of Chs3b was lethal to Fg; disruption of the other Chs gene family members generated knockout mutants with diverse impacts on Fg. Comparative expression analyses revealed that among the Chs gene family members, Chs3b had the highest expression levels during Fg colonization of wheat. Three hairpin RNAi constructs corresponding to the different regions of Chs3b were found to silence Chs3b in transgenic Fg strains. Co‐expression of these three RNAi constructs in two independent elite wheat cultivar transgenic lines conferred high levels of stable, consistent resistance (combined type I and II resistance) to both FHB and FSB throughout the T₃ to T₅ generations. Confocal microscopy revealed profoundly restricted mycelia in Fg‐infected transgenic wheat plants. Presence of the three specific short interfering RNAs in transgenic wheat plants was confirmed by Northern blotting, and these RNAs efficiently down‐regulated Chs3b in the colonizing Fusarium pathogens on wheat seedlings and spikes. Our results demonstrate that host‐induced gene silencing of an essential fungal chitin synthase gene is an effective strategy for enhancing resistance in crop plants under field test conditions.     

Degradation of toluene by ortho cleavage enzymes in Burkholderia fungorum FLU100

Burkholderia fungorum FLU100 simultaneously oxidized any mixture of toluene, benzene and mono‐halogen benzenes to (3‐substituted) catechols with a selectivity of nearly 100%. Further metabolism occurred via enzymes of ortho cleavage pathways with complete mineralization. During the transformation of 3‐methylcatechol, 4‐carboxymethyl‐2‐methylbut‐2‐en‐4‐olide (2‐methyl‐2‐enelactone, 2‐ML) accumulated transiently, being further mineralized only after a lag phase of 2 h in case of cells pre‐grown on benzene or mono‐halogen benzenes. No lag phase, however, occurred after growth on toluene. Cultures inhibited by chloramphenicol after growth on benzene or mono‐halogen benzenes were unable to metabolize 2‐ML supplied externally, even after prolonged incubation. A control culture grown with toluene did not show any lag phase and used 2‐ML as a substrate. This means that 2‐ML is an intermediate of toluene degradation and converted by specific enzymes. The conversion of 4‐methylcatechol as a very minor by‐product of toluene degradation in strain FLU100 resulted in the accumulation of 4‐carboxymethyl‐4‐methylbut‐2‐en‐4‐olide (4‐methyl‐2‐enelactone, 4‐ML) as a dead‐end product, excluding its nature as a possible intermediate. Thus, 3‐methylcyclohexa‐3,5‐diene‐1,2‐diol, 3‐methylcatechol, 2‐methyl muconate and 2‐ML were identified as central intermediates of productive ortho cleavage pathways for toluene metabolism in B. fungorum FLU100.     

The Ubiquitin Proteasome System Plays a Role in Venezuelan Equine Encephalitis Virus Infection

Many viruses have been implicated in utilizing or modulating the Ubiquitin Proteasome System (UPS) to enhance viral multiplication and/or to sustain a persistent infection. The mosquito-borne Venezuelan equine encephalitis virus (VEEV) belongs to the Togaviridae family and is an important biodefense pathogen and select agent. There are currently no approved vaccines or therapies for VEEV infections; therefore, it is imperative to identify novel targets for therapeutic development. We hypothesized that a functional UPS is required for efficient VEEV multiplication. We have shown that at non-toxic concentrations Bortezomib, a FDA-approved inhibitor of the proteasome, proved to be a potent inhibitor of VEEV multiplication in the human astrocytoma cell line U87MG. Bortezomib inhibited the virulent Trinidad donkey (TrD) strain and the attenuated TC-83 strain of VEEV. Additional studies with virulent strains of Eastern equine encephalitis virus (EEEV) and Western equine encephalitis virus (WEEV) demonstrated that Bortezomib is a broad spectrum inhibitor of the New World alphaviruses. Time-of-addition assays showed that Bortezomib was an effective inhibitor of viral multiplication even when the drug was introduced many hours post exposure to the virus. Mass spectrometry analyses indicated that the VEEV capsid protein is ubiquitinated in infected cells, which was validated by confocal microscopy and immunoprecipitation assays. Subsequent studies revealed that capsid is ubiquitinated on K48 during early stages of infection which was affected by Bortezomib treatment. This study will aid future investigations in identifying host proteins as potential broad spectrum therapeutic targets for treating alphavirus infections.     

Gene survival in the Asian wild horse (Equus przewalskii): I. Dependence of gene survival in the calgary breeding group pedigree

The joint probability distribution of the number of distinct (not identical by descent) genes from each founder of the Equus przewalskii population that survive in the five horses of the Calgary Zoological Gardens breeding group has been calculated. The dependence structure of this distribution is investigated, and informative marginal distributions are given, among them the distributions of the genetic contributions of each founder to the Calgary horses and the distribution of wild-type genes in these horses. The dependence pattern is found to be complex; there is no substitute for exact calculation of the full joint probability distribution of numbers of surviving genes. Probabilities of gene survival give a more complete summary of the genetic structure of a set of individuals than is provided by more routine measures such as heterozygosity or founder contributions. The feasibility of computing these probabilities for small groups of current individuals descended from few founders via long and complex pedigrees, provides a new approach to assessing such groups, and could be used also in selecting animals to form the founder stock of propagules for future reintroduction programs.     

Effects of heterogeneous interaction strengths on food web complexity

Using a bioenergetic model we show that the pattern of foraging preferences greatly determines the complexity of the resulting food webs. By complexity we refer to the degree of richness of food-web architecture, measured in terms of some topological indicators (number of persistent species and links, connectance, link density, number of trophic levels, and frequency of weak links). The poorest food-web architecture is found for a mean-field scenario where all foraging preferences are assumed to be the same. Richer food webs appear when foraging preferences depend on the trophic position of species. Food-web complexity increases with the number of basal species. We also find a strong correlation between the complexity of a trophic module and the complexity of entire food webs with the same pattern of foraging preferences.     

Expression of nonstructural rotavirus protein NSP4 mimics Ca2+ homeostasis changes induced by rotavirus infection in cultured cells

Rotavirus infection modifies Ca²⁺ homeostasis, provoking an increase in Ca²⁺ permeation, the cytoplasmic Ca²⁺ concentration ([Ca²⁺]_cyto), and total Ca²⁺ pools and a decrease in Ca²⁺ response to agonists. A glycosylated viral protein(s), NSP4 and/or VP7, may be responsible for these effects. HT29 or Cos-7 cells were infected by the SA11 clone 28 strain, in which VP7 is not glycosylated, or transiently transfected with plasmids coding for NSP4-enhanced green fluorescent protein (EGFP) or NSP4. The permeability of the plasma membrane to Ca²⁺ and the amount of Ca²⁺ sequestered in the endoplasmic reticulum released by carbachol or ATP were measured in fura-2-loaded cells at the single-cell level under a fluorescence microscope or in cell suspensions in a fluorimeter. Total cell Ca²⁺ pools were evaluated as ⁴⁵Ca²⁺ uptake. Infection with SA11 clone 28 induced an increase in Ca²⁺ permeability and ⁴⁵Ca²⁺ uptake similar to that found with the normally glycosylated SA11 strain. These effects were inhibited by tunicamycin, indicating that inhibition of glycosylation of a viral protein other than VP7 affects the changes of Ca²⁺ homeostasis induced by infection. Expression of NSP4-EGFP or NSP4 in transfected cells induced the same changes observed with rotavirus infection, whereas the expression of EGFP or EGFP-VP4 showed the behavior of uninfected and untransfected cells. Increased ⁴⁵Ca²⁺ uptake was also observed in cells expressing NSP4-EGFP or NSP4, as evidenced in rotavirus infection. These results indicate that glycosylated NSP4 is primarily responsible for altering the Ca²⁺ homeostasis of infected cells through an initial increase of cell membrane permeability to Ca²⁺.     

Identification of the most significant amphipathic helix with application to HIV and MHV envelope proteins

Amphipathic helices, which play important roles in protein structure,occur in a wide variety of lengths. Yet existing methods employfixed window lengths. We present a hierarchical procedure thatidentifies the Q most significant amphipathic helices regardlessof length. Since the observed hydrophobicities are not normallydistributed, test statistics usually employed for least-squaresregression are inappropriate for assessing statistical significanceof amphipathic helices. We show that an adjusted F statisticprovides a good test. An application to the envelope proteinof HIV finds an unexpected long amphipathic helix in gp41. Received on July 12, 1989; accepted on February 28, 1990     

SLLP1, a unique,intra-acrosomal,non-bacteriolytic,c lysozyme-like protein of human spermatozoa

We report the presence of a unique, non-bacteriolytic, c (chicken or conventional type) lysozyme-like protein, SLLP1, in the acrosome of human sperm. C lysozymes are bacteriolytic and can also bind to N-acetylglucosamines linked by beta-1,4 glycosidic bonds. Most of the invariant residues (17 out of 20), including all the cysteines, were conserved in SLLP1, but the two catalytic residues E35 and D52 of c lysozymes were replaced with T and N, respectively. The full-length cDNA encodes a protein of 215 aa with a predicted protease cleavage site between A87 and K88. The processed form of SLLP1, which showed an exon-intron organization similar to human c lysozyme, was the major isoform in the acrosome of ejaculated sperm. As expected, based on its sequence, the mature protein secreted from yeast showed no bacteriolytic activity. A significant decrease (54%, P < or = 0.001) in the number of sperm bound to zona-free hamster eggs was observed in the presence of antisera to recombinant SLLP1. SLLP1 mRNA (size, approximately 1 kb) appeared to be expressed only in the testis and in the Burkitt lymphoma Raji cell line. The gene SPACA3 encodes SLLP1 and contains five exons at locus 17q11.2. Because of its typical c lysozyme-like sequence, genomic organization, conservation of putative substrate-binding sites even in the absence of catalytic residues, and localization in the acrosomal matrix, we hypothesize that, after acrosome reaction, SLLP1 could be a potential receptor for the egg oligosaccharide residue N-acetylglucosamine, which is present in the extracellular matrix over the egg plasma membrane, within the perivitelline space, pores of zona pellucida, and cumulus layers.