Functional expression of the lipase gene Lip2 of <Emphasis Type="Italic">Pleurotus</Emphasis> <Emphasis Type="Italic">sapidus</Emphasis> in <Emphasis Type="Italic">Escherichia</Emphasis> <Emphasis Type="Italic">coli</Emphasis>

The lipase Lip2 of the edible basidiomycete, Pleurotus sapidus, is an extracellular enzyme capable of hydrolysing xanthophyll esters with high efficiency. The gene encoding Lip2 was expressed in Escherichia coli TOP10 using the gene III signal sequence to accumulate proteins in the periplasmatic space. The heterologous expression under control of the araBAD promoter led to the high level production of recombinant protein, mainly as inclusion bodies, but partially in a soluble and active form. A fusion with a C-terminal His tag was used for purification and immunochemical detection of the target protein. This is the first example of a heterologous expression and periplasmatic accumulation of a catalytically active lipase from a basidiomycete fungus.     

<Emphasis Type="Italic">Carex</Emphasis> × <Emphasis Type="Italic">involuta</Emphasis> and <Emphasis Type="Italic">Carex juncella</Emphasis> in the flora of Slovakia

The paper brings information on an isolated occurrence and morphological characters of Carex × involuta and C. juncella populations in the Vel’ká Fatra Mts. Their presence has been known neither from the territory of Slovakia nor from the whole Western Carpathians till now.     

Blooms of the invasive ctenophore, <Emphasis Type="Italic">Mnemiopsis</Emphasis> <Emphasis Type="Italic">leidyi</Emphasis>, span the Mediterranean Sea in 2009

Blooms of the invasive ctenophore, Mnemiopsis leidyi, occurred in 2009 along the Mediterranean Sea coasts of Spain and Israel. This voracious zooplanktivore spread throughout the Black Sea basin after its introduction in the early 1980s, throughout northern European coastal waters, and now occurs throughout the Mediterranean Sea. M. leidyi occurred throughout the summer along the entire Catalan Spanish and Israeli coasts in 2009. Those locations had high temperatures (18–26°C) and salinities (37–38) during the blooms. The patterns of abundance of large jellyfish along the Catalan coast were unusual in 2009, with low numbers during July, August, and September when ctenophores were abundant. Small populations of those potential predators and food competitors of M. leidyi could have contributed to the ctenophore bloom. The identity of the ctenophores from Spain and Israel was confirmed as M. leidyi by molecular analysis based on DNA sequencing of the nuclear internal transcribed spacer (ITS) regions. This is the first molecular confirmation of M. leidyi in the Mediterranean Sea. Most ctenophores had an ITS genotype previously found in M. leidyi from other invaded regions (the Black, Azov, and Mediterranean seas), as well as native regions in the United States, suggesting common ancestry. Based on the circulation patterns of Mediterranean surface waters and shipping activities, we conclude that the spread of M. leidyi in the Mediterranean probably resulted from re-introductions by ballast water transport and subsequent distribution by currents. We also conclude that the near-simultaneous blooms in opposite ends of both the Mediterranean basins indicate that M. leidyi is resident around the Mediterranean. We discuss environmental conditions, food, and predators of M. leidyi in both regions that would influence the future effects of this voracious consumer on the pelagic food web of the Mediterranean Sea.     

Significant ecosystem-wide effects of the swiftly spreading invasive freshwater bivalve <Emphasis Type="Italic">Limnoperna</Emphasis> <Emphasis Type="Italic">fortunei</Emphasis>

Since its introduction in South America around 1990, the freshwater Asian mussel Limnoperna fortunei has been shown to strongly interact with several components of the local biota. However, investigation of its ecosystem-wide effects was hindered by (1) difficulties associated with evaluation of its densities over large spatial scales and (2) scarcity of pre-invasion environmental data. The present survey overcomes these shortcomings and addresses the question whether Limnoperna’s impact on the ecosystem-wide scale is measurable and significant. On the basis of diver-collected bottom samples, we estimated the overall density of this mussel in a reservoir (Embalse de Río Tercero, Argentina), where Limnoperna is present since 1998 and analyzed changes in several water-column properties before and after the invasion. The 47 km² reservoir hosts around 45 billion mussels; at these densities, a volume equivalent to that of this water body can potentially be filtered by the bivalves every 2–3 days. Data collected regularly since 1996 indicate that after the invasion water transparency increased, and suspended matter, chlorophyll a, and primary production decreased significantly, with strong changes occurring in the area with highest mussel densities. Our results indicate that the ecosystem-wide impacts of Limnoperna are generally comparable to those described in Europe and North America for another invasive mussel—Dreissena polymorpha. However, given Limnoperna’s wider tolerance limits, its influence on newly invaded water bodies, potentially including Europe and North America, will probably be stronger.     

Brood cell size of <Emphasis Type="Italic">Apis</Emphasis> <Emphasis Type="Italic">mellifera</Emphasis> modifies the reproductive behavior of <Emphasis Type="Italic">Varroa</Emphasis> <Emphasis Type="Italic">destructor</Emphasis>

We undertook a field study to determine whether comb cell size affects the reproductive behavior of Varroa destructor under natural conditions. We examined the effect of brood cell width on the reproductive behavior of V. destructor in honey bee colonies, under natural conditions. Drone and worker brood combs were sampled from 11 colonies of Apis mellifera. A Pearson correlation test and a Tukey test were used to determine whether mite reproduction rate varied with brood cell width. Generalized additive model analysis showed that infestation rate increased positively and linearly with the width of worker and drone cells. The reproduction rate for viable mother mites was 0.96 viable female descendants per original invading female. No significant correlation was observed between brood cell width and number of offspring of V. destructor. Infertile mother mites were more frequent in narrower brood cells.     

Influence of the macrophyte <Emphasis Type="Italic">Eichhornia azurea</Emphasis> on fish assemblage of the Upper Paraná River floodplain (Brazil)

The architecture of aquatic macrophytes adds structural complexity to the littoral region. This increased habitat heterogeneity prompts greater diversity and stability of biotic communities. However, there are few studies that explore the ecological role of macrophytes in the Neotropical region. Then, the aim of this study was to determine spatial and diel influence of near-shore Eichhornia azurea stands on fish assemblage attributes and structure, in the Upper Paraná River floodplain, considering a meso-habitat scale. To achieve this objective, fish were trapped in four stands of macrophytes, in three positions (middle and border of the stand and open area) with samplings taken at different times of the day (6 h, 12 h and 18 h). A total of 537 fish of 16 species were caught. Dissolved oxygen varied significantly among positions. Fish assemblage attributes (species richness, evenness and Shannon Diversity Index) also varied among positions. Fish assemblage structure (summarized by a detrended correspondence analysis) and size structure were strongly influenced by times of the day and positions. The patterns observed can be explained by factors such as oxygen concentration, food resource availability and predation, all influenced by macrophytes. We suggest that any strategy to manage fish diversity and fish stocks has to consider aquatic macrophytes.     

Testing hypotheses on the origin and dispersion of <Emphasis Type="Italic">Limnoperna fortunei</Emphasis> (Bivalvia,Mytilidae) in the Iguassu River (Paraná, Brazil): molecular markers in larvae and adults

The invasive bivalve Limnoperna fortunei (Dunker 1857) was introduced in South America in 1991, with the first occurrence in Brazil in 1998. In the Iguassu River, the species was recorded in 2001; however, it is unknown how it was introduced and spread. Adults and larvae were sampled in Iguassu and Paraná Rivers, and the genetic profiles were compared. The species was absent in the upper reaches and only larvae were found, in low densities, in intermediary reaches. The L. fortunei populations from the lower Iguassu River presented no genetic differentiation among themselves, suggesting strong connectivity, and were significantly different from the Paraná River populations, most likely because of Iguassu Falls. Furthermore, the results suggest that the Paraná River represents the source of propagules to the Iguassu River. Generally, no significant differences were observed between the genetic structure inferred from adults and larvae. Only the population from the Iguassu National Park, a lotic environment, differed from the remaining subpopulations. The characterization of genetic profile using larval stages of L. fortunei populations was satisfactory, and represents an important protocol for studying the population genetics of aquatic species with planktonic larval stages.     

<Emphasis Type="Italic">Astyanax</Emphasis> <Emphasis Type="Italic">bockmanni</Emphasis> Vari and Castro, 2007: an ambiguous karyotype in the <Emphasis Type="Italic">Astyanax</Emphasis> genus

Despite the widespread distribution of Astyanax bockmanni in streams from Upper Paraná River system in central, southeastern, and southern Brazil, just recently, it has been identified as a distinct Astyanax species. Cytogenetic studies were performed in two populations of this species, revealing conservative features. A. bockmanni shows 2n = 50 chromosomes, a karyotypic formula composed of 10 M + 12SM + 12ST + 16A and multiple Ag-NORs. Eight positive signals in subtelocentric/acrocentric chromosomes were identified by fluorescent in situ hybridization (FISH) with 18S rDNA probes. After FISH with 5S rDNA probes, four sites were detected, comprising the interstitial region of a metacentric pair and the terminal region on long arms of another metracentric pair. Little amounts of constitutive heterochromatin were observed, mainly distributed at distal region in two chromosomal pairs. Additionally, heterochromatin was also located close to the centromeres in some chromosomes. No positive signals were detected in the chromosomes of A. bockmanni by FISH with the As-51 satellite DNA probe. The studied species combines a set of characteristics previously identified in two different Astyanax groups. The chromosomal evolution in the genus Astyanax is discussed.     

<Emphasis Type="Italic">In vitro</Emphasis> and <Emphasis Type="Italic">in vivo</Emphasis> inhibition of α-amylases of stored-product mite <Emphasis Type="Italic">Acarus siro</Emphasis>

The stored-product mites are the most abundant and frequent group of pests living on the stored food products in Europe. They endanger public health since they produce allergens and transmit mycotoxin-producing fungi. Novel acaricidal compounds with inhibitory effects on the digestive enzymes of arthropods are a safe alternative to the traditional neurotoxic pesticides used for control of the stored-product pests. In this work, we explored the properties of acarbose, the low molecular weight inhibitor of -amylases (AI), as a novel acaricide candidate for protection of the stored products from infestation by Acarus siro (Acari: Acaridae). In vitro analysis revealed that AI blocked efficiently the enzymatic activity of digestive amylases of A. siro, and decreased the physiological capacity of mites gut in utilizing a starch component of grain flour. In vivo experiments showed that AI suppressed the population growth of A. siro. The mites were kept for three weeks on experimental diet enriched by AI in concentration range of 0.005 to 0.25%. Population growth of A. siro was negatively correlated with the content of AI in the treated diet with a half-population dose of 0.125%. The suppressive effect of AIs on stored-product mites is discussed in the context of their potential application in GMO crops     

New family of pectinase genes <Emphasis Type="Italic">PGU1</Emphasis>b–<Emphasis Type="Italic">PGU3b</Emphasis> of the pectinolytic yeast <Emphasis Type="Italic">Saccharomyces bayanus</Emphasis> var. <Emphasis Type="Italic">uvarum</Emphasis>

Using yeast genome databases and literature data, we have conducted a phylogenetic analysis of pectinase PGU genes from Saccharomyces strains assigned to the biological species S. arboricola, S. bayanus (var. uvarum), S. cariocanus, S. cerevisiae, S. kudriavzevii, S. mikatae, S. paradoxus, and hybrid taxon S. pastorianus (syn. S. carlsbergensis). Single PGU genes were observed in all Saccharomyces species, except S. bayanus. The superfamily of divergent PGU genes has been documented in S. bayanus var. uvarum for the first time. Chromosomal localization of new PGU1b, PGU2b, and PGU3b genes in the yeast S. bayanus var. uvarum has been determined by molecular karyotyping and Southern hybridization.     

Heterologous expression of a gene for thermostable xylanase from <Emphasis Type="Italic">Chaetomium</Emphasis> <Emphasis Type="Italic">thermophilum</Emphasis> in <Emphasis Type="Italic">Pichia</Emphasis> <Emphasis Type="Italic">pastoris</Emphasis> GS115

We studied heterologous expression of xylanase 11A gene of Chaetomium thermophilum in Pichia pastoris and characterized the thermostable nature of the purified gene product. For this purpose, the xylanase 11A gene of C. thermophilum was cloned in P. pastoris GS115 under the control of AOX1 promoter. The maximum extracellular activity of recombinant xylanase (xyn698: gene with intron) was 15.6 U ml⁻¹ while that of recombinant without intron (xyn669) was 1.26 U ml⁻¹ after 96 h growth. The gene product was purified apparently to homogeneity level. The optimum temperature of pure recombinant xylanase activity was 70°C and the enzyme retained its 40.57% activity after incubation at 80°C for 10 min. It exhibited quite lower demand of activation energy, enthalpy, Gibbs free energy, entropy, and xylan binding energy during substrate hydrolysis than that required by that of the donor, thus indicating its thermostable nature. pH-dependent catalysis showed that it was quite stable in a pH range of 5.5–8.5. This revealed that gene was successfully processed in P. pastoris and remained heat stable and may qualify for its potential use in paper and pulp and animal feed applications.     

Disruption of the GPI Protein-Encoding Gene <Emphasis Type="Italic">IFF4</Emphasis> of <Emphasis Type="Italic">Candida</Emphasis> <Emphasis Type="Italic">albicans</Emphasis> Results in Decreased Adherence and Virulence

Candida albicans is the most important cause of systemic fungal infection in immunocompromised humans. Candidiasis is often initiated by the adherence and the colonization of inert surfaces such as peripheral venous catheters, central catheters, prosthetic cardiac valves, and other prostheses. We have studied the early stage of adherence and have shown that the disruption of C. albicans IFF4 gene encoding a GPI-anchor protein, led to a decrease of adherence of the germ tubes to plastic. Here, we demonstrated the role of the IFF4 gene in adherence to silicone catheter, as well as in virulence using a murine model of disseminated candidiasis. The iff4 Δ null mutant showed both a decrease of adherence to silicone catheter and a reduction of virulence. This work presents evidence for the importance of the IFF4 gene in host-fungal interaction.     

Butterfly diversity in Mediterranean islands and in Pentadaktylos <Emphasis Type="Italic">Pinus</Emphasis><Emphasis Type="BoldItalic"> </Emphasis><Emphasis Type="Italic">brutia</Emphasis> forests of Cyprus

We analysed the influence of contemporary geography on butterfly diversity for islands in the Mediterranean Basin. We found that island size and distance from the mainland has a significant effect on the number of species. We also used butterflies as an indicator group to identify the importance of forest habitats for biodiversity conservation in the island of Cyprus. To understand the relative importance of local vegetation characteristics of butterflies in the Pentadaktylos mountains transect counts were used to assess the abundance and butterfly diversity in two different forest types. A total of 1,602 butterflies and 23 species were recorded during this research. We observed highly significant effects of forest type on abundance and species richness of butterflies. For example, number of butterflies was significantly higher in old forest than young pine forest. Also, the abundance of endemic butterflies was highest in old forest habitats. Therefore, the survival of the majority of endemic butterflies in Cyprus may depend on conservation of old forests and their understorey plants.     

Is the <Emphasis Type="Italic">Mnr</Emphasis> locus of Triticeae species the same as the <Emphasis Type="Italic">Ndh</Emphasis> and <Emphasis Type="Italic">Dia</Emphasis> loci?

The menadione reductase (MNR), the nicotinamide adenine dinucleotide dehydrogenase (NDH) and diaphorase (DIA) isozymes were studied in the allohexaploid Triticum aestivum cv ”Chinese Spring” and in five diploid Triticeae species. The Mnr1, Ndh3 and Dia1 loci were located on the chromosome arms 3AL, 3BL and 3DL of T. aestivum, respectively. These loci were also located on the 3H chromosome of Hordeum vulgare cv ”Betzes”, the 3L chromosome of Aegilops longissima and the 6RL chromosome arm of Secale cereale cv ”Imperial”. The chromosomal location results together with the segregation studies support a tetrameric behaviour of the MNR1, NDH3 and DIA1 isozymes. The Ndh1 and Dia3 loci were located on homoeologous group 4 showing a monomeric behaviour. The chromosomal locations and linkage data of the Mnr, Ndh and Dia loci suggest that Mnr1=Ndh3=Dia1; Ndh1=Dia3 and Ndh2=Dia2. Received: 3 June 2001 / Accepted: 11 July 2001     

Chromosome polymorphism in <Emphasis Type="Italic">Rineloricaria pentamaculata</Emphasis> (Loricariidae,Siluriformes) of the Paraná River basin

Cytogenetic analysis in three Rineloricaria pentamaculata populations revealed diploid number 2n = 56 chromosomes, karyotype formula 8m/sm + 48st/a and FN = 64. Owing to the presence of the heteromorphic chromosome pair with a big submetacentric chromosome and a small acrocentric one in both males and females, 42.9% of specimens in the Tauá Stream population had the karyotype formula 9m/sm + 47st/a and FN = 65. Analysis of the nucleolus-organizing region by Ag-NOR and FISH techniques showed a single NOR system at pair 5 for R. pentamaculata populations of the Keller River and the Tauá Stream. However, specimens of populations of the Tatupeba Stream had multiple NOR systems at pairs 5 and 8. A constitutive heterochromatin pattern in R. pentamaculata is mainly distributed in the pericentromeric and telomeric regions with interstitial markers in certain chromosomes. Heterochromatin is located in the telomeric and centromeric positions of the acrocentric chromosome in the heteromorphic pair of the Tauá Stream population. In the submetacentric chromosome the markings are located in the telomeric (short arm), pericentomeric and interstitial (long arm) positions. The origins of polymorphisms are discussed.     

Molecular variation of the testes-specific β<Emphasis Type="Italic">NACtes</Emphasis> genes in the <Emphasis Type="Italic">Drosophila melanogaster</Emphasis> genome

The βNACtes gene family of the Drosophila melanogaster genome provides a model for investigating the mechanisms of the molecular evolution of recently evolved genes. The βNACtes genes code for proteins that are homologous to the subunit of the nascent polypeptide-associated complex (NAC), are expressed exclusively in the testis, and are localized on the X chromosome as two-gene clusters and one separate copy. Population polymorphism of the βNACtes genes was studied using several wild-type D. melanogaster stocks, and βNACtes paralogs were compared with each other. A heterogeneous pattern was observed for βNACtes polymorphism: the 3′ genes of the two-gene clusters were low polymorphic, whereas, separate, the βNACtes1 gene was the most variable. The 5′ βNACtes copies of the two-gene tandems were practically identical, whereas the 3′ βNACtes copies were highly diverged. Hence, local gene conversion was assumed to provide for the selective homogenization of the 5′ genes. A comparison of the βNACtes paralogs showed that the majority of amino acid differences were in the N-terminal region, containing the βNAC domain. The McDonald-Kreitman test was used to analyze the divergence of βNACtes paralogs and implicated positive selection in the evolution of the βNACtes gene family.     

The <Emphasis Type="Italic">GAL10</Emphasis> Gene is Located 40 kbp Away from the <Emphasis Type="Italic">GAL7</Emphasis>-<Emphasis Type="Italic">GAL1</Emphasis> Region in the Yeast <Emphasis Type="Italic">Kazachstania naganishii</Emphasis>

Of the genes involved in galactose metabolism, GAL7, GAL10, and GAL1 are tightly linked in this order on chromosome II in Saccharomyces cerevisiae. While several species of the order Saccharomycetales have similar gene organization, Kazachstania naganishii is unique, in which GAL7 and GAL1 are close to each other whereas GAL10 is substantially apart from them on chromosome XI. In this study, we inserted the recognition sequence of I-SceI homing-endonuclease into GAL10 and also into the intervening segment of GAL7-GAL1. By cleaving chromosome DNA of the gene-manipulated strain with I-SceI, we obtained evidence that chromosome XI (610 kbp) was replaced with three fragments (305, 265, and 40 kbp). Using appropriate probes, we further found that GAL10 was about 40 kbp apart from the GAL7-GAL1 cluster and that orientation of GAL10 was reversed comparing to the S. cerevisiae counter part. We, therefore, contend that comparison of the organization of the GAL cluster among Saccharomycetales is of importance to elucidate evolution of chromosomes and that the experimental scheme developed in this study is useful for this line of investigation.