Sex-specific dispersal in spatially varying environments leads to habitat-dependent evolutionary stable offspring sex ratios

When the environment varies spatially, so that some habitatsare more favorable to reproduction than others, an individualshould attempt to increase the number of offspring establishingin high-quality habitats. Hence, if male and female dispersalbehavior differ, it may be adaptive to produce more offspringof the more dispersing sex in low-quality habitats, since these offspring are likely to disperse to another patch, and moreoffspring of the most philopatric sex in high-quality habitats,since these offspring are likely to remain in that patch. Sucha strategy is shown to be evolutionarily stable provided thatmale and female dispersal rates are different and that reproductivesuccess varies between habitats (lack of ideal free distribution).Highly biased sex ratios are predicted (1) in rare habitats, (2) in poor habitats, (3) when difference between habitat qualityis large, (4) when at least one sex disperses at a rate closeto random with respect to habitat availability, (5) when bothsexes disperse at a high rate, (6) when individuals are unableto select their reproducing habitat, and, presumably, (7) withmoderate temporal variation of habitat quality. The model appearsto be a good candidate to explain the pattern of sex ratiovariation in a variety of species : phytophagous arthropods,species with environmental sex determination, and territorialpasserines.     

A drug-resistant mutation in plant target of rapamycin validates the specificity of ATP-competitive TOR inhibitors in vivo

Kinases are major components of cellular signaling pathways, regulating key cellular activities through phosphorylation. Kinase inhibitors are efficient tools for studying kinase targets and functions, however assessing their kinase specificity in vivo is essential. The identification of resistant kinase mutants has been proposed to be the most convincing approach to achieve this goal. Here, we address this issue in plants via a pharmacogenetic screen for mutants resistant to the ATP-competitive TOR inhibitor AZD-8055. The eukaryotic TOR (Target of Rapamycin) kinase is emerging as a major hub controlling growth responses in plants largely thanks to the use of ATP-competitive inhibitors. We identified a dominant mutation in the DFG motif of the Arabidopsis TOR kinase domain that leads to very strong resistance to AZD-8055. This resistance was characterized by measuring root growth, photosystem II (PSII) activity in leaves and phosphorylation of YAK1 (Yet Another Kinase 1) and RPS6 (Ribosomal protein S6), a direct and an indirect target of TOR respectively. Using other ATP-competitive TOR inhibitors, we also show that the dominant mutation is particularly efficient for resistance to drugs structurally related to AZD-8055. Altogether, this proof-of-concept study demonstrates that a pharmacogenetic screen in Arabidopsis can be used to successfully identify the target of a kinase inhibitor in vivo and therefore to demonstrate inhibitor specificity. Thanks to the conservation of kinase families in eukaryotes, and the possibility of creating amino acid substitutions by genome editing, this work has great potential for extending studies on the evolution of signaling pathways in eukaryotes.     

Functional Constraints on Insect Immune System Components Govern Their Evolutionary Trajectories

Roles of constraints in shaping evolutionary outcomes are often considered in the contexts of developmental biology and population genetics, in terms of capacities to generate new variants and how selection limits or promotes consequent phenotypic changes. Comparative genomics also recognizes the role of constraints, in terms of shaping evolution of gene and genome architectures, sequence evolutionary rates, and gene gains or losses, as well as on molecular phenotypes. Characterizing patterns of genomic change where putative functions and interactions of system components are relatively well described offers opportunities to explore whether genes with similar roles exhibit similar evolutionary trajectories. Using insect immunity as our test case system, we hypothesize that characterizing gene evolutionary histories can define distinct dynamics associated with different functional roles. We develop metrics that quantify gene evolutionary histories, employ these to characterize evolutionary features of immune gene repertoires, and explore relationships between gene family evolutionary profiles and their roles in immunity to understand how different constraints may relate to distinct dynamics. We identified three main axes of evolutionary trajectories characterized by gene duplication and synteny, maintenance/stability and sequence conservation, and loss and sequence divergence, highlighting similar and contrasting patterns across these axes amongst subsets of immune genes. Our results suggest that where and how genes participate in immune responses limit the range of possible evolutionary scenarios they exhibit. The test case study system of insect immunity highlights the potential of applying comparative genomics approaches to characterize how functional constraints on different components of biological systems govern their evolutionary trajectories.     

Partial purification and characterization of two isoenzymes involved in the sulfurylation of catecholamines

To elucidate the specificity of the enzymatic system involved in the sulfurylation of catecholamines, the purification of the enzyme(s) from canine liver was undertaken. Ion-exchange chromatography led to the resolution of two sulfotransferases A and B with different pH optima for dopamine (6 for A and 9.5 for B). The apparent K_m values for 3′-phosphoadenosine 5′-phosphosulfate and dopamine were 1.7 μM and 17.7 μM for enzyme A and 26 μM and 6.2 μM for enzyme B. Each enzyme has a molecular weight of 60 000 while their isoelectric points differ; 5.7 for A and 4.7 for B. The enzyme B catalyzes the sulfurylation of a wider range of substrates than A which is preferentially active with dopamine. These results suggest the presence of two isoenzyme forms of sulfotransferase in canine liver.     

Isochromosome 17q in two cases of acute blast transformation in myeloproliferative disorders

Summary Two case of acute blast cell transformation in myeloproliferative disorders associated with a dicentric 17q isochromosome are reported. In both cases, the karyotypes also also included a Philadelphia 9q;22q translocation, and in one case, an additional chromosome 8 (trisomy 8).     

Functional Interaction between the Bovine Papillomavirus Virus Type 1 Replicative Helicase E1 and Cyclin E-Cdk2

We have found that the replicative helicase E1 of bovine papillomavirus type 1 (BPV-1) interacts with a key cell cycle regulator of S phase, the cyclin E-Cdk2 kinase. The E1 helicase, which interacts with cyclin E and not with Cdk2, presents the highest affinity for catalytically active kinase complexes. In addition, E1, cyclin E, and Cdk2 expressed in Xenopus egg extracts are quantitatively coimmunoprecipitated from crude extracts by either anti-Cdk2 or anti-E1 antibodies. E1 protein is also a substrate of the cyclin E-Cdk2 kinase in vitro. Using the viral components required for in vitro BPV-1 replication and free-membrane cytosol from Xenopus eggs, we show that efficient replication of BPV plasmids is dependent on the addition of E1-cyclin E-Cdk2 complexes. Thus, the BPV initiator of replication and cyclin E-Cdk2 are likely to function together as a protein complex which may be the key to the cell cycle regulation of papillomavirus replication.     

Variation in the stopover duration of Reed Warblers Acrocephalus scirpaceus in Morocco: effects of season, age and site

To test the prediction that stopover duration reflects the rate of body mass gain during stopover, the relationship between these two parameters was investigated in the Reed Warbler Acrocephalus scirpaceus at two sites in Morocco, Sidi Bou Ghaba on the Atlantic coast, and Kerbacha on the Mediterranean coast. Estimation of stopover duration was made using the recently published method by M. Schaub et al . We investigated effects of age and site on stopover parameters during autumn and spring migration. Stopover duration was longer for juveniles than for adults, longer at the Atlantic site than at the Mediterranean site and longer in autumn than in spring. Altogether, estimated stopover duration was longer than expected from previous studies based on minimum stopover duration. Body mass gain varied inconsistently among site, season and age classes, without a clear relation to stopover duration. This suggests that stopover duration is not dependent only on the rate of body mass gain.