Social structure and indirect genetic effects: genetics of social behaviour

The social environment modulates gene expression, physiology, behaviour and patterns of inheritance. For more than 50 years, this concept has been investigated using approaches that include partitioning the social component out of behavioural heritability estimates, studying maternal effects on offspring, and analysing dominance hierarchies. Recent advances have formalized this ‘social environment effect’ by providing a more nuanced approach to the study of social influences on behaviour while recognizing evolutionary implications. Yet, in most of these formulations, the dynamics of social interactions are not accounted for. Also, the reciprocity between individual behaviour and group‐level interactions has been largely ignored. Consistent with evolutionary theory, the principles of social interaction are conserved across a broad range of taxa. While noting parallels in diverse organisms, this review uses Drosophila melanogaster as a case study to revisit what is known about social interaction paradigms. We highlight the benefits of integrating the history and pattern of interactions among individuals for dissecting molecular mechanisms that underlie social modulation of behaviour.     

Development and use of striped bass-specific RFLP probes

We sought to develop nuclear DNA (nDNA) probes which could be used to complement mtDNA and DNA fingerprinting markers in distinguishing striped bass, Morone saxatilis (Walbaum), from discrete spawning systems. Restriction endonuclease-generated single copy, 10–20-kb striped bass nuclear nDNA fragments were cloned into the bacteriophage vector Lambda Dash II and tested in Southern blot analyses for their abilities to reveal population-specific polymorphisms. Three of the I7 nDNA sequences tested exhibited polymorphisms which potentially could be used to delineate striped bass populations. One probe, DSB 22, revealed significant genotypic frequency differences between Gulf of Mexico and Atlantic striped bass and among striped bass representative of some Atlantic systems. These preliminary results suggest that single copy nDNA sequences may provide sufficient polymorphisms to aid in stock identification of species which proved genetically monomorphic using other approaches.     

Some new variants of serum protease inhibitors in Meishan pigs

Serum samples of Meishan (13 animals) and Meishan x Wild Boar crosses (361 animals) were analysed by means of two-dimensional electrophoresis. Some new variants in protease inhibitor systems PO1A, PO1B and PI2 are reported.     

The evolution of intrinsic reproductive isolation in the genus Cakile (Brassicaceae)

In theory, adaptive divergence can increase intrinsic post‐zygotic reproductive isolation (RI), either directly via selection on loci associated with RI, or indirectly via linkage of incompatibility loci with loci under selection. To test this hypothesis, we measured RI at five intrinsic post‐zygotic reproductive barriers between 18 taxa from the genera Cakile and Erucaria (Brassicaceae). Using a comparative framework, we tested whether the magnitude of RI was associated with genetic distance, geographic distance, ecological divergence and parental mating system. Early stages of post‐zygotic RI related to F₁ viability (i.e. initial seed set) tended to be stronger than later stages related to F₁ fecundity (i.e. flower number, fruit number). Mating system significantly influenced early stages of RI, such that RI was lowest when the mother was selfing and father was outcrossing, consistent with an imbalance between sink strength and resistance to provisioning. We found little evidence that adaptive divergence accelerates the evolution of intrinsic post‐zygotic RI, consistent with a nonecological model of evolution that predicts the nonlinear accumulation of RI and RI asymmetry with time (i.e. genetic distance), irrespective of adaptive divergence. Thus, although certain aspects of ecological divergence do not appear to have contributed strongly to the evolution of RI in this system, divergence in mating system actually reduced RI, suggesting that mating system evolution may play a significant role in speciation dynamics.     

A testis‐specific gene within a widely expressed gene: Contrasting evolutionary patterns of two differentially expressed mammalian proteins encoded by a single gene,CAMK4

Understanding the patterns of genetic variations within fertility‐related genes and the evolutionary forces that shape such variations is crucial in predicting the fitness landscapes of subsequent generations. This study reports distinct evolutionary features of two differentially expressed mammalian proteins [CaMKIV (Ca²⁺/calmodulin‐dependent protein kinase IV) and CaS (calspermin)] that are encoded by a single gene, CAMK4. The multifunctional CaMKIV, which is expressed in multiple tissues including testis and ovary, is evolving at a relatively low rate (0.46–0.64 × 10^?9 nucleotide substitutions/site/year), whereas the testis‐specific CaS gene, which is predominantly expressed in post‐meiotic cells, evolves at least three to four times faster (1.48–1.98 × 10^?9 substitutions/site/year). Concomitantly, maximum‐likelihood‐based selection analyses revealed that the ubiquitously expressed CaMKIV is constrained by intense purifying selection and, therefore, remained functionally highly conserved throughout the mammalian evolution, whereas the testis‐specific CaS gene is under strong positive selection. The substitution rates of different mammalian lineages within both genes are positively correlated with GC content, indicating the possible influence of GC‐biased gene conversion on the estimated substitution rates. The observation of such unusually high GC content of the CaS gene (≈74%), particularly in the lineage that comprises the bovine species, suggests the possible role of GC‐biased gene conversion in the evolution of CaS that mimics positive selection.     

Drought‐stress and plant resistance affect herbivore performance and proteome: the case of the green peach aphid Myzus persicae (Hemiptera: Aphididae)

Little is known about the simultaneous effects of drought stress and plant resistance on herbivorous insects. By subjecting the green peach aphid Myzus persicae Sulzer to well‐watered and drought‐stressed plants of both susceptible and resistant peach (Prunus persica), the effects of both stressors on aphid performance and proteomics are tested. Overall, the influence of the water treatment on aphid performance is less pronounced than the effect of host plant genetic resistance. On the susceptible cultivar, aphid survival, host acceptance and ability to colonize the plant do not depend on water treatment. On the resistant cultivar, aphid survival and ability to colonize are higher on drought‐stressed than on well‐watered plants. A study examining the pattern of protein expression aiming to explain the variation in aphid performance finds higher protein expression in aphids on the drought‐stressed susceptible cultivars compared with the well‐watered ones. In the susceptible cultivar, the regulated proteins are related to energy metabolism and exoskeleton functionality, whereas, in the resistant cultivar, the proteins are involved with the cytoskeleton. Comparison of the protein expression ratios for resistant versus susceptible plants reveals that four proteins are down‐regulated in well‐watered plants and 15 proteins are down‐regulated in drought‐stressed plants. Drought stress applied to the susceptible cultivar induces the regulation of proteins in M. persicae that enable physiological adaptation to maintain an almost unaltered aphid performance. By contrast, for aphids on the resistant cultivar subjected to drought stress, the down‐regulation of proteins responds to an induced host susceptibility effect.     

Sensing cellular biochemistry with fluorescent chemical–genetic hybrids

Fluorescent biosensors are powerful tools for the detection of biochemical events inside cells with high spatiotemporal resolution. Biosensors based on fluorescent proteins often suffer from issues with photostability and brightness. On the other hand, hybrid, chemical–genetic systems present unique opportunities to combine the strengths of synthetic, organic chemistry with biological macromolecules to generate exquisitely tailored semisynthetic sensors.