Utility of the white gene in estimating phylogenetic relationships among mosquitoes (Diptera: Culicidae)

The utility of a nuclear protein-coding gene for reconstructing phylogenetic relationships within the family Culicidae was explored. Relationships among 13 species representing three subfamilies and nine genera of Culicidae were analyzed using a 762-bp fragment of coding sequence from the eye color gene, white. Outgroups for the study were two species from the sister group Chaoboridae. Sequences were determined from clone PCR products amplified from genomic DNA, and aligned following conceptual intron splicing and amino acid translation. Third codon positions were characterized by high levels of divergence and biased nucleotide composition, the intensity and direction of which varied among taxa. Equal weighting of all characters resulted in parsimony and neighboring-joining trees at odds with the generally accepted phylogenetic hypothesis based on morphology and rDNA sequences. The application of differential weighting schemes recovered the traditional hypothesis, in which the subfamily Anophelinae formed the basal clade. The subfamily Toxorhynchitinae occupied an intermediate position, and was a sister group to the subfamily Culicinae. Within Culicinae, the genera Sabethes and Tripteroides formed an ancestral clade, while the Culex-Deinocerites and Aedes- Haemagogus clades occupied increasingly derived positions in the molecular phylogeny. An intron present in the Culicinae- Toxorhynchitinae lineage and one outgroup taxon was absent in the basal Anophelinae lineage and the second outgroup taxon, suggesting that intron insertions or deletions may not always be reliable systematic characters.      

Nucleo-cytoplasmic interaction between oligomycin-resistant mutations in Saccharomyces cerevisiae

1.A single-gene nuclear mutant of Saccharomyces cerevisiae, isolated as oligomycin-resistant, exhibits in vivo cross-resistance to venturicidin and collateral sensitivity to Synthalin. All three compounds are inhibitors of mitochondrial oxidative phosphorylation. Oligomycin resistance and Synthalin sensitivity are recessive, while venturicidin resistance is dominant. 2. Acytoplasmic mutant, also isolated as oligomycin-resistant, shows collateral sensitivity to both Synthalin and venturicidin. All three traits undergo mitotic segregation in diploids formed by crossing mutant and normal halpoids. 3. A novel nucleocytoplasmic interaction is observed in diploids formed by crossing haploid strains containing the nuclear and the cytoplasmic mutations, respectively. The dominant venturicidin resistance determined by the nuclear gene undergoes mitotic segregation, which results from a suppression of the nuclear phenotype by the cytoplasmic mutation. When a diploid mitotic segregant contains primarily mutant-type mitochondria, venturicidin resistance is completely suppressed. In haploids containing both the nuclear and cytoplasmic mutations, suppression is only partial. 4. Oxidative phosphorylation and ATPase in mitochondrial fractions isolated fromcytoplasmic mutant cells are less sensitive to inhibition by oligomycin than normal, but in vitro sensitivity to venturicidin is not significantly changed. In similar mitochondrial fractions isolated from normal and nuclear mutant cells, no significant differences in sensitivity to either inhibitor are detected. 5. The molecular basis for the nucleocytoplasmic suppression of venturicidin resistance may involve participation of mitochondrial membrane, plasma membrane or both. Either mitochondria can undergo changes in venturicidin sensitivity upon isolation, or the molecular entity which controls access of venturicidin to the mitochondria resides outside of the organelles. 6. Our data establish that aspects of the response in vivo of both venturicidin and Snythalin are controlled by the mitochondrial genome. 7. The nucleocytoplasmic interaction described here is the first example in which a specific restricted mitochondrial mutation modifies the phenotypic expression of a nuclear gene.     

Cloning of an endoglucanase gene fromPseudomonas fluorescens var.cellulosa intoEscherichia coli andPseudomonas fluorescens

Summary An endoglucanase chromosomal gene from the cellulolyticPseudomonas fluorescens var.cellulosa (NCIB 10462) was cloned inEscherichia coli. Chromosomal DNA was partially digested with the restriction enzymeEcoRI and ligated into the broad host-range, mobilizable plasmid pSUP104 that had been linearized with the same enzyme. After transformation ofEscherichia coli, and endoglucanase-positive clone was detected in situ by use of the Congo-red assay procedure. The endoglucanase gene on the recombinant plasmid pRUCL 100 was expressed in the non-cellulolyticPseudomonas fluorescens PF41. The DNA fragment carrying the gene was transferred to the plasmid pBR322, generating plasmids pRUCL150 and pRUCL151, and its restriction map was derived.Abbreviations CMC carboxymethylcellulose - EG endoglucanase - kb kilobase pairs - Mops 4-morpholinepropanesulfonic acid - Ap^r-s resistance-sensitivity to the antibiotic ampicillin - Cm^r-s resistance-sensitivity to the antibiotic chloramphenicol - Tc^r-s resistance-sensitivity to the antibiotic tetracycline - Sm^r-s resistance-sensitivity to the antibiotic streptomycin - Tp^r-s resistance-sensitivity to the antibiotic trimethoprim     

Cloning, nucleotide sequence and expression in Escherichia coli of a lipase gene from Bacillus subtilis 168.

The gene coding for an extracellular lipase of Bacillus subtilis 168 was cloned and found to be expressed in Escherichia coli. Enzyme activity measurements showed no fatty acid chain length preference. A set of Tn5 insertions which inactivate the gene were localized and used to initiate its sequencing. The nucleotide sequence was determined on two independent clones expressed in E. coli. In one of these clones, the sequence revealed a frameshift, due to the presence of an additional adenine in the N-terminal region, which caused the interruption of the open reading frame, probably allowing translation to initiate at a second ATG codon. The sequence of the wild-type lip gene from B. subtilis was confirmed on the chromosomal fragment amplified by polymerase chain reaction (PCR). When compared to other lipases sequenced to date, the enzyme described here lacks the conserved pentapeptide Gly-X-Ser-X-Gly supposed to be essential for catalysis. However, alignments of several microbial lipase sequences suggest that the pentapeptide Ala-X-Ser-X-Gly present in the lipase B. subtilis may function as the catalytic site. Homologies were found in the N-terminal protein region with lipases from different Pseudomonas species. The predicted M(r) and isoelectric point for the mature protein are 19,348 and 9.7 respectively.     

Comparative study of the condensation of chicken erythrocyte and calf thymus chromatins by di- and multivalent cations

The condensation of chicken erythrocyte (CE) and calf thymus (CT) chromatins upon addition of di- and multivalent cations has been studied using turbidity, precipitation and electric dichroism measurements. For all the cations investigated (Mg2+, Tb3+, Co(NH3)6(3+), spermidine Spd2+ and spermine Sp4+) condensation of CE chromatin occurred before the onset of aggregation, while aggregation of CT chromatin started before condensation with all cations except Mg2+ and Tb3+. Precipitation of CE chromatin required lower di- and multivalent cations concentrations than CT chromatin. The electric dichroism data for both chromatins, at low ionic strength in the absence of di- or multivalent cations, indicated that the nucleoprotein molecules were not totally decondensed but that a "precondensed" state was already present. A positive electric dichroism was observed for the most condensed chromatin fibers, in agreement with the "cross-linker" models. Tb3+ led to less compact condensed particles as judged from the electric dichroism observations, but electron microscopy revealed that "30 nm fibers" were formed. Very little aggregation was produced by Tb3+. On the contrary, spermine produced very large networks of condensed molecules, but large spheroidal particles were also observed. The condensation of CE chromatin happened without changes of solution conductivity upon cation salt addition, regardless of the condensing cation, indicating a cooperative uptake of the ions during this process.     

Chronic Uncertainty and Momentary Opportunity: A half century of adaptation among Zambia’s Gwembe Tonga

In Zambia’s Southern Province, where a history of climatic and political fluctuation have played out in peoples livelihood choices and ecological impacts, the Gwembe Tonga people have learned to respond to uncertainty by expecting the worst. This outlook emerges from at least 50 years of experience. The building of the Kariba Dam on the Middle Zambezi River in the late 1950s resulted in the forced relocation of Gwembe people. Since resettlement in 1958, Gwembe people have lived under conditions of increasing uncertainty, both environmental and sociopolitical, that have enormous implications for environmental change. Understanding environmental change in this region demands an exploration of the social, political and economic context of Gwembe Tonga lives. In looking for broad patterns of adaptation and response, one point emerges clearly. For the Gwembe Tonga, the most recurrent pattern, and most reliable response to living in conditions of extreme uncertainty, is an increasingly opportunistic use of the environment and other resources. This article presents ethnographic data collected over more than 50 years (through the Gwembe Tonga Research Project) in Southern Zambia.     

Allelism relationships between diuron-resistant, antimycin-resistant and funiculosin-resistant loci of the mitochondrial map in Saccharomyces cerevisiae.

Summary Using allelism tests, two diuron (DIU1, DIU2), one funiculosin (FUN1), and two antimycin (ANA1, ANA2) resistance loci are resolved into two mitochondrial drug-resistant genetic loci. DIU1 is allelic to ANA2 and FUN1. DIU2 is allelic to ANA1.Chercheur qualifié du Fonds National de la Recherche Scientifique