A. M. Kulikov

The endosymbiotic bacterium Wolbachia enhances the nonspecific resistance to insect pathogens and alters behavior of Drosophila melanogaster

To determine biologically important effects of the cytoplasmic endosymbiont Wolbachia, two substrains of the same Drosophila melanogaster strain have been studied, one of them infected with Wolbachia and the other treated with tetracycline to eliminate the bacterium. Females of D. melanogaster infected with Wolbachia are more resistant to the fungus Blauveria bassiana (an insect pathogen) than uninfected females; infected females also exhibited changes in oviposition substrate preference. Males infected with the bacterium are more competitive than uninfected males. The possible role of Wolbachia in the formation of alternative ecological strategies of D. melanogaster is discussed.

Aggression, digit ratio, and variation in the androgen receptor, serotonin transporter, and dopamine D4 receptor genes in African foragers: the Hadza.

The role of genes in the expression of aggression and masculinity traits in humans has been a focus of recent behavioral genetic studies. This is the first study on the variation in aggression, the digit ratio (the ratio between the second and the fourth digits, 2D:4D), the directional asymmetry in 2D:4D (DR-L) and polymorphisms of the AR, DRD4, and 5-HTTL genes in simple hunter-gatherers, namely the Hadza of Tanzania (142 adult men). The distribution of AR, DRD4E3, and 5-HTTLPR genotypes and allele frequencies in Hadza was compared to other African populations on which the data were available. Hadza and Ariaal differed significantly in the distributions of frequencies of AR alleles with different numbers of CAG repeats. Hadza population was similar to other African populations in the distribution of allelic frequencies of the DRD4E3 locus, and to Afro-Americans in the distribution of allelic types of the 5-HTTLPR locus. We found no influence of AR gene on the right hand 2D:4D ratio, DR-L, and any of aggression subscales of the Buss-Perry Aggression Questionnaire (AQ). Although, a weak positive correlation between CAG repeats and the left hand 2D:4D was found. The multiple regression analysis with digit ratios, DR-L and aggression subscales of AQ as dependent variables and the three gene candidates (AR, DRD4E3, and 5-HTTLPR) as independent variables revealed the following: men with lower number of CAG repeats had significantly lower left hand 2D:4D ratio; men with higher numbers of 48-bp unit copies in exon 3 of a VNTR polymorphism in the DRD4 gene had significantly lower digit ratios on both hands; no effect of the 5-HTTLPR gene on either the digit ratio or aggressive behavior. These findings demonstrate the complexity of gene effects on digit ratios and aggression and call for simultaneous analysis of more candidate genes. It is noteworthy that these results were obtained for a human population that is still practicing foraging and has been subjected to a high selective pressure due to harsh environments and practically has no access to modern medical care. Hadza are highly egalitarian, and their culture does not favor persons with a dominant or aggressive behavior. It is still to be found to what extent the relationships observed in this study are similar to those in other human populations.

Symbiotic bacteria affect mating choice in Drosophila melanogaster

Mating preferences depending on Wolbachia infection were studied in two genotypically different strains of Drosophila melanogaster. Females from both strains carry two attached X chromosomes. Males from the red-eyed strain (R) have the wild-type X chromosome compared to males from the white-eyed strain (W), whose X chromosome contains two deleterious mutations (white and singed). Three types of competition tests showed that assortative mating depends on genotype, infection status and their combination in the mating partners. Males of strain R, genetically closer to the wild type, were more successful than males of strain W. Wolbachia infection increased the mating ability of W males but did not affect that of R males. Strain W showed positive assortative mating (preference for ‘self’) with regard to genotype and infection status. In strain R, negative assortative mating (preference for ‘nonself’) was observed. Moreover, the most affected flies (infected W) showed higher preference for ‘self’, while the least affected ones (uninfected R) showed higher preference for ‘nonself’. These results support the idea that mating choice may involve testing the partner for degree of genetic or biochemical similarity with self, based on chemoreception with possible participation of immune system components.

The Phylogeny of Triticum L. and Aegilops L. Inferred from Comparative Analysis of Nucleotide Sequences in rDNA Promoter Regions

The process of accumulation of knowledge on wheat and related wild species during the 20th century is briefly reviewed with special reference to the evidence of the recent years on evolution of polyploid wheats and the role of diploid species. The latter serve as potential donors of the genomes, detection of which is particularly important because of the continuing speciation in the tribe Triticeae and artificial development of synthetic forms. The arguments in favor of the donor role for various diploid wheat and aegilops species from the section Sitopsis are compared. It is stated that in the formation of the both lines of polyploid wheats turgidum–aestivumand timopheevi,diploid Aegilops speltoides acted as a maternal form. In addition to cytoplasmic genomes, this aegilops species introduced into them also the B and G nuclear subgenomes. A comparison of nucleotide sequences in the variable part of the promoter of evolutionary conserved rRNA genes in polyploid wheats with their counterparts in diploid wheats and aegilops species confirmed the accepted wheat phylogenies.

Aggression and polymorphisms in AR, DAT1, DRD2, and COMT genes in Datoga pastoralists of Tanzania

The aim of this study was to analyse the relationships between polymorphisms in four candidate genes (AR, DAT1, DRD2, and COMT) and aggression in men from a traditional society of East African pastoralists, the Datoga. Buss and Perrys Aggression Questionnaire was used to measure aggression. The number of CAG repeats in the AR gene was negatively correlated with physical aggression, anger, and hostility. Among the genes of the dopaminergic system, a significant single-gene effect was detected only for DRD2 with regard to anger. At the level of a two-gene model, a significant effect for DRD2 and a tendency for DAT1 were observed for the DAT1-DRD2 gene pair regarding hostility, and two tendencies were observed for the interaction effect of the DAT1-COMT pair regarding anger and hostility. These data suggest a probable link between physical aggression and direct fitness caused by strong sexual selection in Datoga men.

Polymorphism of the dopamine D4 receptor (DRD4) and serotonin transporter (5-HTTL) gene promoter regions in african tribes of Hadza and Datoga

Molecular genetic analysis of the allelic variants of the DRD4 and 5-HTTL gene promoter regions was performed in African tribes of Hadza and Datoga, characterized by different levels of socially acceptable aggression. It was demonstrated that Hadza and Datoga people differed in the structural organization of one of the 5-HTTL alleles (extra long allele xL). Analysis of the allele length polymorphism of both genes showed that in the Hadza and Datoga samples examined, variation parameters, as well as the genotype and allele frequency distribution pattern were almost the same. At the same time, analysis of the SNP polymorphism at the A/G substitutions of the 5-HTTL locus revealed a substantial decrease of the active allele LA frequency in the population of Hadza compared to the population of Datoga (χ2 = 3.77; d.f. = 1; p = 0.052).

Morphometric Analysis of Male Genitalia in Sibling Species of Drosophila virilis Sturt.

The structure of male genital organs in sibling species of the virilis group of Drosophila was examined using methods of multivariate statistics. The differences among these species were estimated using 33 indices and 2 angle parameters. The intraspecific and interspecific correlation structure of the examined characters and the order of their divergence were established. The key characters with respect to forming interspecific differences in the virilis species group were identified. Based on these results, the relative systematic positions of the sibling species are discussed as well as similarities and differences of the pattern of relationships among the species from that generally accepted for the virilis group.

A RAPD fingerprinting of sibling species of the Drosophila virilis group

A comparative analysis of the sibling species of Drosophila virilis was performed by RAPD-PCR technique using a set of random primers. The degree of relatedness was studied by cluster analysis (UPGMA) and multidimensional scaling. The resulting pattern of species relationships contradicts the classical taxonomy. The main result of the cluster analysis is that D. virilis does not cluster with the remaining three species of its phylad, while according to multidimensional scaling, D. virilis is equidistant from all the species of its group, from both the species of its phylad and the species of the montana phylad. The montana phylad is extremely heterogeneous; moreover, the species D. littoralis, D. ezoana, and D. kanekoi appear to be closer to the virilis phylad than to the other species of the montana phylad, wherein these species are traditionally included. The phylogenetic relationships between the studied species discovered using RAPD fingerprinting comply with the results obtained using protein markers and quantitative traits.

The effect of population density on the elimination dynamics of a recessive lethal mutation l(2)M167DTS from experimental populations of Drosophila melanogaster

Dynamics of the elimination of the temperature-sensitive lethal mutation l(2)M167DTS from experimental populations of Drosophila melanogaster under permissive conditions (25°C) was studied. We have shown a rapid elimination of the mutation from the populations, selection for fitness of heterozygous individuals, association of the selection with high larval density and with the direction of the cross that had produced the founder males of the l(2)M167DTS/+ population, and the effect of relative competitive ability of l(2)M167DTS/+ males on the efficiency of the mutation introduction. Modification systems were shown be involved in fitness selection under conditions of high larval density.

[Comparative Analysis of Polymorphisms of the Serotonin Receptor Genes HTR1A, HTR2A, and HTR1B in Hadza and Datoga Males].

The distribution of the allele and genotype frequencies of polymorphic loci of serotonin receptor genes (HTR1A, rs6295; HTR2A, rs6311; HTR1B, rs6296) in Hadza (n = 197) and Datoga males (n = 230) living in Tanzania was determined. It was shown that the populations significantly differ by the frequencies of alleles and genotypes of the rs6295 locus of the HTR1A gene. The G-allele (0.779) and the genotype G/G (0.590), which are markers of increased risk of suicidal and impulsive behavior, respectively, are revealed in Hadza with high frequency. It was found that the frequency of homozygous G/G of the rs6296 locus of the HTR1B gene, which is a marker of increased risk of outward directed aggression, is higher in Datoga (0.563) than in Hadza (0.457). The allele and genotype frequencies of the rs6311 locus of the HTR2A gene do not differ among the Hadza and Datoga males. The data on the distribution of allele and genotype frequencies of the HTR1A, HTR2A, and HTR1B genes can be used to determine the associations of the identified markers with various forms of human aggressive behavior.