Modelling intraspecific resting egg shape variation in a freshwater fairy shrimp Tanymastix stagnalis (L., 1758) (Crustacea, Branchiopoda)

The shape of the resting eggs of a large branchiopod crustacean, the Anostraca Tanymastix stagnalis , is represented very accurately by analytical expressions. The occurrence of atypical shape of some T. stagnalis eggs may be viewed as a simple change of the analytical expression describing the usual egg shape. Their unusual shape may be explained by a higher embryo volume within an envelope of a given size. Biological implications are briefly discussed and hypothesized in an evolutionary point of view.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 55–60.     

Adult movements between populations in the specialist butterfly Proclossiana eunomia (Lepidoptera, Nymphalidae)

Abstract.

• 1 The structure of local populations of a monophagous butterfly, the bog fritillary Proclossiana eunomia, was studied in a complex of suitable habitat patches separated by spruce plantations or fertilized pasture.
• 2 An unexpected high level of adult movements between habitat patches was detected by a mark—release—recapture technique. Local populations were connected by adult movements across unsuitable habitats, leading to a meta-population structure.
• 3 This evidence of the metapopulation structure of a specialist butterfly challenges the supposed relationship between habitat specialization and closed, isolated populations.
• 4 Males and females of P.eunomia exhibited different spatial behaviours; females were more likely to emigrate and dispersed further than males. These differences in spatial behaviour are related to the mating system.

     

Isolation and characterization of tetranucleotide microsatellite markers in a mouth‐brooding haplochromine cichlid fish (Pseudocrenilabrus multicolor victoriae) from Uganda

Eight tetranucleotide microsatellite loci were isolated from the haplochromine cichlid fish, Pseudocrenilabrus multicolor victoriae, an important model species for studies in respiratory ecology, conservation, and evolution. We surveyed variation at these loci in 23 individuals from western Uganda, finding four to 19 alleles per locus and an average expected heterozygosity of 0.8575. These microsatellite loci will be used to examine gene flow and population structure in Ugandan P. m. victoriae.     

Stability and transformations of bis-PNA/DNA triplex structural isomers

Structurally isomeric complexes formed between homopyrimidine bis-PNAs (T(2)JT(2)JT(4)-linker-T(4)CT(2)CT(2)) and single- and double-stranded DNA targets were investigated. These complexes are triplexes designated S1, S2 and S3 in order of increased mobility by polyacrylamide gel electrophoresis. It is shown that the S3 isomer is formed only on double-stranded DNA and possesses highest stability. Isomers S2 and S1 are formed upon binding of bis-PNA to double-stranded as well as to single-stranded DNA. It was found that the stability of the isomer S1 increases dramatically in the presence of excess single-stranded oligonucleotide complementary to the bis-PNA. The structure of the stabilized S1 isomer is proposed to consist of two bis-PNA/DNA triplexes. The relationship between the yield of the isomer S1 formed on single-stranded DNA and the bis-PNA concentration was investigated and a kinetic model of the formation of S1 is presented.     

Substrate water exchange in photosystem II core complexes of the extremophilic red alga Cyanidioschyzon merolae

The binding affinity of the two substrate–water molecules to the water-oxidizing Mn₄CaO₅ catalyst in photosystem II core complexes of the extremophilic red alga Cyanidioschyzon merolae was studied in the S₂ and S₃ states by the exchange of bound ¹⁶O-substrate against ¹⁸O-labeled water. The rate of this exchange was detected via the membrane-inlet mass spectrometric analysis of flash-induced oxygen evolution. For both redox states a fast and slow phase of water-exchange was resolved at the mixed labeled m/z 34 mass peak: k_f = 52 ± 8 s^− 1 and k_s = 1.9 ± 0.3 s^− 1 in the S₂ state, and k_f = 42 ± 2 s^− 1 and k_slow = 1.2 ± 0.3 s^− 1 in S₃, respectively. Overall these exchange rates are similar to those observed previously with preparations of other organisms. The most remarkable finding is a significantly slower exchange at the fast substrate–water site in the S₂ state, which confirms beyond doubt that both substrate–water molecules are already bound in the S₂ state. This leads to a very small change of the affinity for both the fast and the slowly exchanging substrates during the S₂ → S₃ transition. Implications for recent models for water-oxidation are briefly discussed.     

Thermodynamics of the melting of PNA(2)/DNA triple helices.

Equilibrium melting curves were obtained for triplexes, formed by single stranded DNA containing an A10 target with bis-PNA consisting of two T10 decamers. Thermodynamic parameters of melting were determined for Na(+) concentrations 50, 200 and 600mM by two methods. The melting enthalpy Delta H degrees was evaluated from the width of the differential melting curves and from the concentration dependence of the melting temperature. The latter method allowed also evaluating the melting entropy Delta S degrees. The following results were obtained: Delta H degrees = - 137 kcal/M, Delta S degrees = - 368 cal/M.K, Delta G degrees (298)= - 27 kcal/M. No dependence of Delta H degrees, Delta S degrees and Delta G degrees (298) was observed upon ionic strength within the accuracy of the experiment (+/- 10%). The absolute values of Delta H degrees, Delta S degrees and Delta G degrees(298) are 2 to 3 times higher than the published values of corresponding melting parameters for decameric PNA/DNA duplexes of various nucleic base sequences. The origin of the extremely high stability of the triplexes is discussed.     

‘Arctic Crashes:’ Revisiting the Human-Animal Disequilibrium Model in a Time of Rapid Change

The paper introduces a new vision advanced by the recent project, Arctic People and Animal Crashes: Human, Climate and Habitat Agency in the Anthropocene (2014–2015) developed at the Smithsonian Institution. Unlike earlier top-down models of polar animal-climate-people connections that tied changes in Arctic species’ abundance and ranges to alternating warmer and cooler temperatures or high ice/low sea-ice regimes, rapid animal declines (‘crashes’) may be better approached at regional and local scales. This approach is close to Arctic peoples’ traditional vision that animals, like people, live in ‘tribes’ and that they ‘come and go’ according to their relations with the local human societies. As the Arctic changes rapidly and climate/sea-ice/ecotone boundaries shift, we see diverse responses by Arctic people and animals to environmental stressors. I examine recent data on the status of three northern mammal species – caribou/reindeer, Pacific walrus, and polar bear—during two decades of the ongoing Arctic warming. The emerging record may be best approached as a series of local human-animal disequilibria interpreted from different angles by population biologists, indigenous peoples, and anthropologists, rather than a top-down climate-induced ‘crash.’ Such new understanding implies the varying speed of change in the physical, animal, and human domains, which was not factored in the earlier models of climate–animal–people’s interactions.     

Deletion of <Emphasis Type="Italic">psbQ</Emphasis>’ gene in <Emphasis Type="Italic">Cyanidioschyzon merolae</Emphasis> reveals the function of extrinsic <Emphasis Type="Italic">PsbQ</Emphasis>’ in PSII

Key message

We have successfully produced single-cell colonies of C. merolae mutants, lacking the PsbQ’ subunit in its PSII complex by application of DTA-aided mutant selection. We have investigated the physiological changes in PSII function and structure and proposed a tentative explanation of the function of PsbQ’ subunit in the PSII complex.

Abstract

We have improved the selectivity of the Cyanidioschyzon merolae nuclear transformation method by the introduction of diphtheria toxin genes into the transformation vector as an auxiliary selectable marker. The revised method allowed us to obtained single-cell colonies of C. merolae, lacking the gene of the PsbQ’ extrinsic protein. The efficiency of gene replacement was extraordinarily high, allowing for a complete deletion of the gene of interest, without undesirable illegitimate integration events. We have confirmed the absence of PsbQ’ protein at genetic and protein level. We have characterized the physiology of mutant cells and isolated PSII protein complex and concluded that PsbQ’ is involved in nuclear regulation of PSII activity, by influencing several parameters of PSII function. Among these: oxygen evolving activity, partial dissociation of PsbV, regulation of dimerization, downsizing of phycobilisomes rods and regulation of zeaxanthin abundance. The adaptation of cellular physiology appeared to favorite upregulation of PSII and concurrent downregulation of PSI, resulting in an imbalance of energy distribution, decrease of photosynthesis and inhibition of cell proliferation.

     

A novel mutation in the <Emphasis Type="Italic">AGXT</Emphasis> gene causing primary hyperoxaluria type I: genotype–phenotype correlation

Primary hyperoxaluria type I (PH1) is an autosomal recessive metabolic disorder caused by inherited mutations in the AGXT gene encoding liver peroxisomal alanine : glyoxylate aminotransferase (AGT) which is deficient or mistargeted to mitochondria. PH1 shows considerable phenotypic and genotypic heterogeneity. The incidence and severity of PH1 varies in different geographic regions. DNA samples of the affected members from two unrelated Tunisian families were tested by amplifying and sequencing each of the AGXT exons and intron–exon junctions. We identified a novel frameshift mutation in the AGXT gene, the c.406_410dupACTGC resulting in a truncated protein (p.Gln137Hisfs*19). It is found in homozygous state in two nonconsanguineous unrelated families from Tunisia. These molecular findings provide genotype/phenotype correlations in the intrafamilial phenotypic and permit accurate carrier detection, and prenatal diagnosis. The novel p.Gln137Hisfs*19 mutation detected in our study extend the spectrum of known AGXT gene mutations in Tunisia.