Allozyme polymorphism in <Emphasis Type="Italic">Drosophila</Emphasis>

Every population possesses genetic variations which are achieved through gene mutation, genetic recombination, hybridization, gene duplication etc. These genetic variations provide raw materials for evolutionary forces to create a better surviving species. Genetic polymorphism is reflected at every level in the populations, for example, at phenotypic, chromosomal, protein and DNA levels. Protein or enzyme polymorphisms have been well studied in various organisms including Drosophila and humans. Drosophila has proven to be a good model organism for carrying out polymorphism studies. Among the different species of Drosophila, there is a wide variation in the levels of allozyme polymorphisms and heterozygosities which depends upon species, geographical regions, number and nature of loci in question etc. In Drosophila, the average polymorphic enzyme loci and average heterozygosity ranges from 35 to 70 percent and 10 to 20 percent respectively. The genetic differentiation as observed through allozyme or isozyme variation affords an important parameter in evaluating the phylogenetic relationships between different species of Drosophila and also for discussing the adaptive significance of allozyme polymorphisms. Therefore, this review attempts to compile all studies on allozyme polymorphism in Drosophila that have been undertaken so far.     

The status of <Emphasis Type="Italic">Her2</Emphasis> amplification and <Emphasis Type="Italic">Kras</Emphasis> mutations in mucinous ovarian carcinoma

Jayson GC et al. remarked in Lancet that nearly 100% of mucinous ovarian cancer cases have Kras mutation as well as a high frequency of Her2 amplification. Using the Abbott PathVysion Her2 DNA Probe Kit and Kras mutant-enriched PCR Kits (FemtoPath®), 21 samples of primary ovarian mucinous cystadenocarcinomas from Taiwanese patients were examined to determine the status of Her2 amplification and Kras mutations. Our results showed the Her2 amplification rates were 33.33%, while the Kras mutation rates were 61.90%. We present here our results in order to enlighten the readership that the ~100% Kras mutant frequency and the high Her2 amplification rate reported by Jayson et al. may be too exaggerated to be applicable into all populations. Additionally, we report another 2 novel Kras mutations (A11V, V14I).     

The first complete <Emphasis Type="Italic">Mag</Emphasis> family retrotransposons discovered in <Emphasis Type="Italic">Drosophila</Emphasis>

A retrotransposon of the Mag family was found in the Drosophila simulans genome for the first time. We also identified novel transposable elements representing the Mag family in seven Drosophila species. The high similarity between the 3’ and 5’ long terminal repeats in the found copies of transposable elements indicates that their retrotransposition has occurred relatively recently. Thus, the Mag family of retrotransposons is quite common for the genus Drosophila.     

<Emphasis Type="Italic">Fusarium verticillioides</Emphasis> and fumonisin contamination in <Emphasis Type="Italic">Bt</Emphasis> and non-<Emphasis Type="Italic">Bt</Emphasis> maize cultivated in Brazil

Fusarium verticillioides is one of the main pathogens of maize, causing ear and stalk rots. This fungus is also able to produce high levels of fumonisins, which have been linked to various illnesses in humans and animals. Previous studies have shown that maize hybrids genetically modified with the cry genes from the bacterium Bacillus thuringiensis (Bt) presented lower incidence of F. verticillioides and fumonisin levels, presumably through the reduction of insects, which could act as vectors of fungi. The aim of this study was to assess the incidence of F. verticillioides and the concentration of fumonisins in Bt and isogenic non-Bt hybrids (2B710Hx, 30F35YG, 2B710, and 30F35, respectively). The samples of 2B710Hx and 30F35YG presented lower F. verticillioides frequency than 2B710 and 30F35 samples. However, there was no statistical difference between fumonisin contamination when Bt and non-Bt samples were compared (P > 0.05). The results suggest that other environmental parameters could possibly trigger fumonisin production during plant development in the field; consequently, other management strategies should be applied to aid controlling fumonisin contamination in maize.     

Molecular evolution of mobile elements of the <Emphasis Type="Italic">gypsy</Emphasis> group: A homolog of the <Emphasis Type="Italic">gag</Emphasis> gene in <Emphasis Type="Italic">Drosophila</Emphasis>

Retrotransposons of the gypsy group of Drosophila melanogaster that are structurally similar to retroviruses of vertebrates occupy an important place among retroelements of eukaryotes. The infectious abilities of some retrotransposons of this group (gypsy, ZAM, and Idefix) have been demonstrated experimentally, and therefore they are true retroviruses. It is supposed that retrotransposons can evolve acquiring new components, the sources of which remain to be elucidated. In this work, the CG4680gene (Gag related protein, Grp) homologous to gag of retrotransposons of the gypsy group has been identified in the genome of D. melanogaster and characterized. The Grp gene product has a highly conserved structure in different species of the Drosophilidae family and is under of purifying selection, which suggests its important genomic function in Drosophila. In view of the earlier data, it can be concluded that homologous genes of all components of gypsy retrotransposons are present in the Drosophila genome. These genes can be both precursors and products of domestication of retrovirus genes.     

New <Emphasis Type="Italic">slbo</Emphasis>-Gal4 driver lines for the analysis of border cell migration during <Emphasis Type="Italic">Drosophila</Emphasis> oogenesis

Border cell (BC) migration during Drosophila oogenesis is an excellent model for the analysis of the migratory and invasive cell behavior. Most studies on BC migration have exploited a slbo-Gal4 driver to regulate gene expression in these cells or to mark them. Here, we report that the slbo-Gal4 transgene present in the line #6458 from the Bloomington Stock Center is inserted within chickadee (chic), a gene encoding the actin-binding protein Profilin, which promotes actin polymerization and is known to be involved in cell migration. The chic⁶⁴⁵⁸ mutation caused by the transgene insertion behaves as a null chic allele and is homozygous lethal. To evaluate possible effects of chic⁶⁴⁵⁸ on the assessment of BC behavior, we generated new lines bearing the slbo-Gal4 transgene inserted into different second chromosome loci that do not appear to be involved in cell migration. Using these new lines and the slbo-Gal4-chic⁶⁴⁵⁸ line, we defined the functional relationships between the twinfilin (twf) and chic in BC migration. Migration of BCs is substantially reduced by mutations in twf, which encodes an actin-binding protein that inhibits actin filament assembly. The defects caused by twf mutations are significantly suppressed when the slbo-Gal4-chic⁶⁴⁵⁸, but not the new slbo-Gal4 drivers were used. These findings indicate twf and chic interact and function antagonistically during BC migration in Drosophila oogenesis.     

An <Emphasis Type="Italic">Escherichia coli</Emphasis> Strain Producing a Leaderless mRNA from the Chromosomal <Emphasis Type="Italic">lac</Emphasis> Promoter

A special Escherichia coli strain capable of producing a leaderless lacZ mRNA from the chromosomal lac promoter was constructed to study the mechanism of the leaderless mRNA translation. The translation efficiency of this noncanonical mRNA is very low in comparison with the canonical cellular templates, but it increases by one order of magnitude in the presence of chromosomal mutations in the genes encoding ribosomal S1 and S2 proteins. The new strain possesses obvious advantages over the commonly used plasmid constructs (first of all, due to the constant dosage of lacZ gene in the cell) and opens the possibilities of investigation of the specific conditions for the leaderless mRNA translation in vivo using the molecular genetic approaches.     

Interaction between checkpoint genes <Emphasis Type="Italic">RAD9, RAD17, RAD24</Emphasis>, and <Emphasis Type="Italic">RAD53</Emphasis> involved in the determination of yeast <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> sensitivity to ionizing radiation

Mechanisms for genetic control of cell division cycle (checkpoint control) have been studied in most detail in yeast Saccharomyces cerevisiae. To clarify the role of checkpoint genes RAD9, RAD17, RAD24, and RAD53 in cell radioresistance, double mutants were analyzed for cell sensitivity to ionizing radiation. Double mutants carrying mutations in combination with mutation rad9Δ were shown to manifest the epistatic type of interaction. Our results suggest that checkpoint genes RAD9, RAD17, RAD24, and RAD53 belong to a single epistatic group designated RAD9 and govern the same pathway. Genes RAD9 and RAD53 have a positive effect on sensitivity to γ-radiation, whereas RAD17 and RAD24 have a negative effect. Interactions between mutations may differ when considering their sensitivity to γ-radiation and UV light; mutations rad9Δ and rad24Δ were shown to manifest the additive effect in the first case and epistatic effect in the second.     

Conjugative chromosomal gene transfer in <Emphasis Type="Italic">Bacillus subtilis</Emphasis>

Conjugative transfer of 20-kb chromosomal fragment carrying genes encoding tetracycline (tet ^r ) and lincomycin (lin ^r ) resistance in the soil strain Bacillus subtilis 19 is described. Transfer was preceded by this fragment insertion into the large conjugative p19cat plasmid producing a hybrid plasmid. Insertion frequency was 10^?4?10^?5. Then genes tet ^r and lin ^r were transferred to the recipient strains. The transfer of chromosomal genes inserted into the plasmid and plasmid gene cat occurred sequentially and resembled sexduction, which represents chromosomal gene transfer by F′ and R′ plasmids during conjugation in Escherichia coli and other gram negative bacteria.     

<Emphasis Type="Italic">Candida krusei</Emphasis> and <Emphasis Type="Italic">Candida glabrata</Emphasis> reduce the filamentation of <Emphasis Type="Italic">Candida albicans</Emphasis> by downregulating expression of <Emphasis Type="Italic">HWP1</Emphasis> gene

Pathogenicity of Candida albicans is associated with its capacity switch from yeast-like to hyphal growth. The hyphal form is capable to penetrate the epithelial surfaces and to damage the host tissues. Therefore, many investigations have focused on mechanisms that control the morphological transitions of C. albicans. Recently, certain studies have showed that non-albicans Candida species can reduce the capacity of C. albicans to form biofilms and to develop candidiasis in animal models. Then, the objective of this study was to evaluate the effects of Candida krusei and Candida glabrata on the morphogenesis of C. albicans. Firstly, the capacity of reference and clinical strains of C. albicans in forming hyphae was tested in vitro. After that, the expression of HWP1 (hyphal wall protein 1) gene was determined by quantitative real-time PCR (polymerase chain reaction) assay. For both reference and clinical strains, a significant inhibition of the hyphae formation was observed when C. albicans was incubated in the presence of C. krusei or C. glabrata compared to the control group composed only by C. albicans. In addition, the culture mixed of C. albicans-C. krusei or C. albicans-C. glabrata reduced significantly the expression of HWP1 gene of C. albicans in relation to single cultures of this specie. In both filamentation and gene expression assays, C. krusei showed the higher inhibitory activity on the morphogenesis of C. albicans compared to C. glabrata. C. krusei and C. glabrata are capable to reduce the filamentation of C. albicans and consequently decrease the expression of the HWP1 gene.     

Chromosomal locations of U2 snDNA clusters in <Emphasis Type="Italic">Megaleporinus</Emphasis>, <Emphasis Type="Italic">Leporinus</Emphasis> and <Emphasis Type="Italic">Schizodon</Emphasis> (Characiformes: Anostomidae)

The U small nuclear RNA (U snRNA) genes comprise a multigene family and are required for splicing of pre-mRNA. In this paper, we aimed to study the chromosomal location of the U2 snRNA gene in Megaleporinus, Leporinus and Schizodon species, which constitute interesting models for the study of repetitive DNA and genomic evolution in fish once the group comprises species with and without heteromorphic sex chromosomes. The all six species showed 2n?=?54 chromosomes: Megaleporinus elongatus, Megaleporinus macrocephalus, Leporinus striatus, Leporinus friderici, Schizodon borelli and Schizodon isognathus. The U2 snDNA clusters were evident in only one medium-sized submetracentric pair in all analyzed species and this may represent a condition shared by Anostomidae family.     

Role of Arabidopsis <Emphasis Type="Italic">ABF1</Emphasis>/<Emphasis Type="Italic">3</Emphasis>/<Emphasis Type="Italic">4</Emphasis> during <Emphasis Type="Italic">det1</Emphasis> germination in salt and osmotic stress conditions

Key message

Arabidopsis det1 mutants exhibit salt and osmotic stress resistant germination. This phenotype requires HY5, ABF1, ABF3, and ABF4.

Abstract

While DE-ETIOLATED 1 (DET1) is well known as a negative regulator of light development, here we describe how det1 mutants also exhibit altered responses to salt and osmotic stress, specifically salt and mannitol resistant germination. LONG HYPOCOTYL 5 (HY5) positively regulates both light and abscisic acid (ABA) signalling. We found that hy5 suppressed the det1 salt and mannitol resistant germination phenotype, thus, det1 stress resistant germination requires HY5. We then queried publically available microarray datasets to identify genes downstream of HY5 that were differentially expressed in det1 mutants. Our analysis revealed that ABA regulated genes, including ABA RESPONSIVE ELEMENT BINDING FACTOR 3 (ABF3), are downregulated in det1 seedlings. We found that ABF3 is induced by salt in wildtype seeds, while homologues ABF4 and ABF1 are repressed, and all three genes are underexpressed in det1 seeds. We then investigated the role of ABF3, ABF4, and ABF1 in det1 phenotypes. Double mutant analysis showed that abf3, abf4, and abf1 all suppress the det1 salt/osmotic stress resistant germination phenotype. In addition, abf1 suppressed det1 rapid water loss and open stomata phenotypes. Thus interactions between ABF genes contribute to det1 salt/osmotic stress response phenotypes.

     

New sterigmatocystin-producing species of <Emphasis Type="Italic">Aspergillus</Emphasis> section <Emphasis Type="Italic">Versicolores</Emphasis> from indoor air in Croatia

Multilocus DNA sequence-based identification methods raised the number of known species assigned to the Aspergillus section Versicolores. Currently, there are 16 species accepted in the section, including A. amoenus, A. austroafricanus, A. creber, A. cvjetkovicii, A. fructus, A. griseoaurantiacus, A. hongkongensis, A. jensenii, A. protuberus, A. puulaauensis, A. subversicolor, A. sydowii, A. tabacinus, A. tennesseensis, A. venenatus, and A. versicolor. Based on morphological identifications, most of these species were identified as either A. sydowii or A. versicolor, with the latter reported to have a world-wide distribution, growing in many habitats. Aspergillus versicolor has been implicated in health hazards including sick building syndrome, human and animal mycoses, and contamination of food and feed were assigned primarily to this species. A. versicolor is still commonly isolated from indoor surveys, even though species such as A. jensenii and A. creber seem more common. From indoor air samples collected at a grain mill in Croatia, we isolated an undescribed species assigned to the Aspergillus section Versicolores. A polyphasic approach, including sequence-based methods, morphological and physiological studies, was used for species characterization and in this paper is described as Aspergillus pepii. Additionally, sterigmatocystin producing abilities have been confirmed. Based on a combined phylogenetic tree, morphological features and sterigmatocystin producing abilities, A. pepii is closely related to A. versicolor. Further studies should explore the frequency of the species in indoor environments and its medical, industrial, and environmental significance.     

<Emphasis Type="Italic">Diplazium</Emphasis> hybrids involving <Emphasis Type="Italic">D. plantaginifolium</Emphasis> and <Emphasis Type="Italic">D</Emphasis>. <Emphasis Type="Italic">ternatum</Emphasis> from Mexico and Central America

Here we evaluate the origins and relationships of Mexican and Central American Diplazium hybrids derived from crosses involving either D. plantaginifolium or D. ternatum. Based on study of live plants and herbarium specimens, we distinguish D. ×verapax from the similar D. riedelianum and present evidence that the former is a sterile hybrid derived from a cross between D. plantaginifolium and D. werckleanum. We also describe new hybrids, D. ×torresianum and D. ×subternatum from Mexico and northern Central America. Both involve D. ternatum as one parent. Diplazium. cristatum is the other putative parent of D. ×torresianum, and D. plantaginifolium is the second parent of D. ×subternatum. We also designate lectotypes for D. cordovense and D. dissimile.     

Various <Emphasis Type="Italic">Wolbachia</Emphasis> genotypes differently influence host <Emphasis Type="Italic">Drosophila</Emphasis> dopamine metabolism and survival under heat stress conditions

Background

One of the most widespread prokaryotic symbionts of invertebrates is the intracellular bacteria of Wolbachia genus which can be found in about 50% of insect species. Wolbachia causes both parasitic and mutualistic effects on its host that include manipulating the host reproductive systems in order to increase their transmission through the female germline, and increasing the host fitness. One of the mechanisms, promoting adaptation in biological organisms, is a non-specific neuroendocrine stress reaction. In insects, this reaction includes catecholamines, dopamine, serotonin and octopamine, which act as neurotransmitters, neuromodulators and neurohormones. The level of dopamine metabolism correlates with heat stress resistance in Drosophila adults.

Results

To examine Wolbachia effect on Drosophila survival under heat stress and dopamine metabolism we used five strains carrying the nuclear background of interbred Bi90 strain and cytoplasmic backgrounds with different genotype variants of Wolbachia (produced by 20 backcrosses of Bi90 males with appropriate source of Wolbachia). Non-infected Bi90 strain (treated with tetracycline for 3 generations) was used as a control group. We demonstrated that two of five investigated Wolbachia variants promote changes in Drosophila heat stress resistance and activity of enzymes that produce and degrade dopamine, alkaline phosphatase and dopamine-dependent arylalkylamine N-acetyltransferase. What is especially interesting, wMelCS genotype of Wolbachia increases stress resistance and the intensity of dopamine metabolism, whereas wMelPop strain decreases them. wMel, wMel2 and wMel4 genotypes of Wolbachia do not show any effect on the survival under heat stress or dopamine metabolism. L-DOPA treatment, known to increase the dopamine content in Drosophila, levels the difference in survival under heat stress between all studied groups.

Conclusions

The genotype of symbiont determines the effect that the symbiont has on the stress resistance of the host insect.

     

Horizontal transfer of the C-termini of <Emphasis Type="Italic">tccC</Emphasis> genes in <Emphasis Type="Italic">Photorhabdus</Emphasis> and <Emphasis Type="Italic">Xenorhabdus</Emphasis>

The high molecular weight insecticidal toxin complexes (Tcs), including four toxin-complex loci (tca, tcb, tcc and tcd), were first identified in Photorhabdus luminescens W14. Each member of tca, tcb or tcc is required for oral toxicity of Tcs. However, the sequence sources of the C-termini of tccC3, tccC4, tccC6 and tccC7 are unknown. Here, we performed a whole genome survey to identify the orthologs of Tc genes, and found 165 such genes in 14 bacterial genomes, including 40 genes homologous to tccC1-7 in P. luminescens TT01. The sequence sources of the C-termini of tccC2-6 were determined by sequence analysis. Further phylogenetic investigations suggested that the C-termini of 6 tccC genes experienced horizontal gene transfer events.