Increase in viability due to the accumulation of X chromosome mutations in <Emphasis Type="Italic">Drosophila melanogaster</Emphasis> males

To increase our understanding of the role of new X-chromosome mutations in adaptive evolution, single-X Drosophila melanogaster males were mated with attached-X chromosome females, allowing the male X chromosome to accumulate mutations over 28 generations. Contrary to our hypothesis that male viability would decrease over time, due to the accumulation and expression of X-linked recessive deleterious mutations in hemizygous males, viability significantly increased. This increase may be attributed to germinal selection and to new X-linked beneficial or compensatory mutations, possibly supporting the faster-X hypothesis.     

The endosymbiotic bacterium <Emphasis Type="Italic">Wolbachia</Emphasis> enhances the nonspecific resistance to insect pathogens and alters behavior of <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

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.     

The Toll pathway underlies host sexual dimorphism in resistance to both Gram-negative and Gram-positive bacteria in mated <Emphasis Type="Italic">Drosophila</Emphasis>

Background

Host sexual dimorphism is being increasingly recognized to generate strong differences in the outcome of infectious disease, but the mechanisms underlying immunological differences between males and females remain poorly characterized. Here, we used Drosophila melanogaster to assess and dissect sexual dimorphism in the innate response to systemic bacterial infection.

Results

We demonstrated sexual dimorphism in susceptibility to infection by a broad spectrum of Gram-positive and Gram-negative bacteria. We found that both virgin and mated females are more susceptible than mated males to most, but not all, infections. We investigated in more detail the lower resistance of females to infection with Providencia rettgeri, a Gram-negative bacterium that naturally infects D. melanogaster. We found that females have a higher number of phagocytes than males and that ablation of hemocytes does not eliminate the dimorphism in resistance to P. rettgeri, so the observed dimorphism does not stem from differences in the cellular response. The Imd pathway is critical for the production of antimicrobial peptides in response to Gram-negative bacteria, but mutants for Imd signaling continued to exhibit dimorphism even though both sexes showed strongly reduced resistance. Instead, we found that the Toll pathway is responsible for the dimorphism in resistance. The Toll pathway is dimorphic in genome-wide constitutive gene expression and in induced response to infection. Toll signaling is dimorphic in both constitutive signaling and in induced activation in response to P. rettgeri infection. The dimorphism in pathway activation can be specifically attributed to Persephone-mediated immune stimulation, by which the Toll pathway is triggered in response to pathogen-derived virulence factors. We additionally found that, in absence of Toll signaling, males become more susceptible than females to the Gram-positive Enterococcus faecalis. This reversal in susceptibility between male and female Toll pathway mutants compared to wildtype hosts highlights the key role of the Toll pathway in D. melanogaster sexual dimorphism in resistance to infection.

Conclusion

Altogether, our data demonstrate that Toll pathway activity differs between male and female D. melanogaster in response to bacterial infection, thus identifying innate immune signaling as a determinant of sexual immune dimorphism.

     

Locating a modifier gene of <Emphasis Type="Italic">Ovum mutant</Emphasis> through crosses between DDK and C57BL/6J inbred strains in mice

A striking infertile phenotype has been discovered in the DDK strain of mouse. The DDK females are usually infertile when crossed with males of other inbred strains, whereas DDK males exhibit normal fertility in reciprocal crosses. This phenomenon is caused by mutation in the ovum (Om) locus on chromosome 11 and known as the DDK syndrome. Previously, some research groups reported that the embryonic mortality deviated from the semilethal rate in backcrosses between heterozygous (Om/ + ) females and males of other strains. This embryonic mortality exhibited an aggravated trend with increasing background genes of other strains. These results indicated that some modifier genes of Om were present in other strains. In the present study, a population of N₂ (Om/ + ) females from the backcrosses between C57BL/6J (B6) and F₁ (B6 ♀ × DDK ♂) was used to map potential modifier genes of Om. Quantitative trait locus showed that a major locus, namely Amom1 (aggravate modifier gene of Om 1), was located at the middle part of chromosome 9 in mice. The Amom1 could increase the expressivity of Om gene, thereby aggravating embryonic lethality when heterozygous (Om/ +) females mated with males of B6 strain. Further, the 1.5 LOD-drop analysis indicated that the confidence interval was between 37.54 and 44.46 cM, ～6.92 cM. Amom1 is the first modifier gene of Om in the B6 background.     

Comparison of antibiotic resistance and copper tolerance of <Emphasis Type="Italic">Enterococcus</Emphasis> spp. and <Emphasis Type="Italic">Lactobacillus</Emphasis> spp. isolated from piglets before and after weaning

In China, antimicrobials and copper are used extensively as growth-promoting agents for piglets. This study aimed to characterize the role of in-feed copper in the emergence of copper-tolerant and antibiotic-resistant Enterococcus and Lactobacillus isolates in Chinese pig farms. Feces of the same eight piglets from four litters at 7 and 55 days old and their mothers were traced in order to isolate Enterococcus spp. and Lactobacillus spp.. The minimum inhibitory concentrations of 10 antimicrobials and copper sulfate were determined using an agar dilution method. The feed levels of Cu²⁺ for lactating sows, suckling piglets, and weaned piglets were 6, 177, and 18 mg/kg, respectively. All the 136 Enterococcus isolates were sensitive to vancomycin; and the resistance rates to penicillin, enrofloxacin, and high level streptomycin resistance increased significantly after weaning. For the 155 Lactobacillus isolates, the resistance rates to ampicillin, chloramphenicol, tetracycline, and enrofloxacin were significantly higher in weaned piglets. The ratios of copper tolerant Enterococcus and Lactobacillus isolates both increased significantly after weaning (P < 0.05). A phenotypic correlation was observed after classifying the isolates into two groups (CuSO₄ MIC₅₀ < 16 or ≧16 for enterococci; CuSO₄ MIC₅₀ < 12 or ≧12 for lactobacilli) and comparing the antimicrobial-resistant percentage of two groups. On species level, a significant increase of E. faecalis to enrofloxacin was observed in line with the increase of copper MIC (P < 0.05). The findings revealed the changes of the antibiotic resistance and copper tolerance level of enterococci and lactobacilli between suckling and weaned piglets and demonstrated that there might be a strong association between in-feed copper and increased antibiotic resistance in enterococci and lactobacilli in Chinese intensive swine farms.     

Isolation mechanisms in closely related grasshopper species <Emphasis Type="Italic">Chorthippus albomarginatus</Emphasis> and <Emphasis Type="Italic">Ch. oschei</Emphasis> (Orthoptera: Acrididae)

Two closely related grasshopper species Chorthippus albomarginatus and Ch. oschei are known to hybridize in the narrow contact zone at the territory of Ukraine and Moldova. Different isolaton mechanisms providing reproductive isolation between the two species were studied. In choice mating experiments, females of the both species demonstrated a strong assortative mating (80–90% preference for the conspecific males). Comparison of the parental and hybrid viability revealed a reduced hatching and increased larval mortality in F₁ and F₂ hybrids. In choice mating experiments, the hybrid females mated less assortatively than the parental females. An assymmetry was found in mating preferences and in viability of hybrids. The results demonstrate the existence of pre-and post-mating isolation between Ch. albomarginatus and Ch. oschei. A possible fate of the hybrid zone is discussed.     

Grouping Patterns and Competition Among Female <Emphasis Type="Italic">Pan troglodytes schweinfurthii</Emphasis> at Ngogo,Kibale National Park,Uganda

In mammals, access to mates is probably the most important influence on male reproductive success, whereas foraging efficiency is probably the most important influence on female reproductive success Emlen and Oring (Science 197:215–223, 1977). Male chimpanzees (Pan troglodytes) are highly gregarious and form cooperative relationships with other males. In contrast, female social relationships vary within and between populations. Females in most East African populations, e.g., Gombe, Mahale, Kibale-Kanyawara, are less gregarious than males and spend most of their time alone or with only their dependent offspring. Researchers have attributed low female gregariousness to the high potential for feeding competition. I provide the first data on association patterns and agonistic interactions of female chimpanzees (Pan troglodytes schweinfurthii) from the unusually large Ngogo community, Kibale National Park, Uganda. Ngogo females were less gregarious than males, but spent a mean of 64% of their time in association with ≥1 other females and as much time in all-female parties as they did alone. Further, female dyads associated nonrandomly and they formed associative cliques. Association levels within cliques were similar to those among the relatively gregarious West African chimpanzee females at Taï (Pan troglodytes verus) and among bonobo (P. paniscus) females. Agonistic interfemale interactions were extremely rare, and monthly mean party size and the numbers of anestrous females per party do not correlate significantly with fruit availability. Thus, Ngogo females maintained relatively high levels of gregariousness, but avoided detrimental feeding competition by preferentially associating with a small subset of other community females.     

The Effects of Stress-Related Hormones on the Stress Resistance in <Emphasis Type="Italic">Drosophila melanogaster</Emphasis> Carrying Mutation in the <Emphasis Type="Italic">Dilp6</Emphasis> Gene

The heat stress resistance of Drosophila melanogaster females carrying a hypomorphic mutation of the DILP6 insulin-like protein gene (dilp6 ⁴¹ ) under a change in the level of stress-related hormones (juvenile hormone and octopamine) is studied. It is revealed that the dilp6 ⁴¹ mutation decreases the heat stress resistance of mature D. melanogaster females. An experimental decrease in the level of juvenile hormone is shown to restore the stress resistance of mutant females to the level of stress resistance observed in wild type Canton S females. These data suggest that the effects of the dilp6 ⁴¹ mutation on the stress resistance of females are mediated by an increased level of juvenile hormone. An experimental increase in the octopamine level that causes an increase in juvenile hormone level supports this hypothesis: the resistance to heat stress decreases in females of both lines and this decrease is more significant in mutant females than in the control line. Thus, it is established for the first time that the effect of the hypomorphic dilp6 gene mutation on the heat stress resistance of D. melanogaster females is mediated by juvenile hormone.     

The effect of genetic environment on locus-specific instability of the <Emphasis Type="Italic">yellow</Emphasis> gene in the Uman’ population of <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

The effects of genotype of the laboratory strains, C(1)DX, ywf/Y, 23.5 MRF/CyL ⁴, and C(1)DX,yf; π₂, on locus-specific instability in the yellow gene of the strains y ^2-217, y ^2-715, and y ^2-700 from Uman’ population of Drosophila melanogaster was studied. Crosses of the males from Uman’-derived lines with the C(1)DX,ywf/Y females yielded a cascade of derivatives, mostly consisting of y ⁺ and y ² alleles, while their crosses with the 23.5 MRF/CyL ⁴ and C(1)DX,yf; π₂ females mostly resulted in the appearance of y ⁺ and y ¹ derivatives. The genomes of laboratory strains used in the study contained the full-sized hobo elements, which could differ from one another relative to the structure of variable region and affinity to different DNA sequences.     

Life History of <Emphasis Type="Italic">Cochliomyia macellaria</Emphasis> (Fabricius, 1775) (Diptera,Calliphoridae), a Blowfly of Medical and Forensic Importance

The life history traits of blow fly Cochliomyia macellaria (Fabricius, 1775) was studied under semi-controlled laboratory conditions at 29.14°C temperature, 72.53% relative humidity, and 12-h photoperiod. The raw data were analyzed based on the age-stage, two-sex life table, considering the development rates among individuals of both sexes. Cochliomyia macellaria survival rate was 0.43 (♂) and 0.40 (♀), while life expectancy was 17.9 (♂) and 20.9 (♀) days, for adult males and females, respectively. The total fecundity was 681.15 eggs/female, with an average of 3.65 batches/female and 199 eggs/batch. The intrinsic rate of increase (r) was 0.327 days^?1, the finite rate of population increase (λ) was 3.35 days^?1, the mean generation time (T) was 17.15 days, and the net reproduction rate (R ₀ ) was 272.46 offspring/individual. The population parameters found here corroborates that C. macellaria population act as a r selected species under laboratory conditions. Additionally, development data and accumulated degree days (ADD) for each stage of C. macellaria are provided and its implications for the forensic use are discussed.     

Reproductive Biology of <Emphasis Type="Italic">Leptocybe invasa</Emphasis> Fisher &amp; La Salle (Hymenoptera: Eulophidae)

Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae) is an invasive pest in Eucalyptus plantations around the world. The successful colonization of L. invasa is possibly related to its reproductive biology. The objective of this study was to examine the reproductive biology of L. invasa. In Guangxi Province, the sex ratio (proportion of female, 0.99) of L. invasa was female-dominant throughout the year based on natural and artificial infestation. This result was similar to the ratios observed for other geographic populations in China, including those in Fujian (0.99), Guangdong (0.98), Hainan (0.95), Jiangxi (0.96), and Sichuan (0.99). The offspring sex ratio favored females. A large number of females emerged from the galls produced by females, with few males found. Galls on the petioles and midribs of Eucalyptus plants could be caused by newly emerged females with mature eggs. The lengths of the ovariole, spermatheca, common oviduct, and reproductive glands did not differ among L. invasa females, but their lateral oviducts showed differences from 0 to 42 h after emergence, indicating that this insect is proovigenic. These results could explain why L. invasa populations can rapidly increase in invaded areas.     

Volatile essential oil chemical composition of basil (<Emphasis Type="Italic">Ocimum basilicum</Emphasis> L. ‘Green’) cultivated in a greenhouse and micropropagated on a culture medium containing copper sulfate

The objective of this study was to determine the effects of copper sulfate (CuSO₄) on the chemical composition of basil (Ocimum basilicum L. ‘Green’) using static headspace extraction. The basil was cultivated in vitro and ex vitro. The sowing was completed in trays, and the seedlings were transplanted to pots and grown in a protected environment for 180 d. For in vitro cultivation, the seeds were placed on Murashige and Skoog (MS) medium enriched with growth regulators, sucrose, agar, and CuSO₄ (at 0 μM [control], 25 μM, or 75 μM). Volatile organic compounds emitted from the excised leaves were collected by the static headspace technique, and identified by gas chromatography coupled to mass spectrometry (GC/MS). Twenty-six compounds were identified in the leaves harvested from the plants cultivated in vitro, while 11 compounds were identified in the leaves sampled from the ex vitro plants. Oxygenated monoterpenes were the main compounds found in plants cultivated ex vitro. Phenylpropanoids predominated in the control and the 25 μM CuSO₄ treatments. The main compounds found were methyl eugenol (52.03%) and eugenol (20.66%). For the 75 μM CuSO₄ treatment, the major compounds detected were linalool (28.14%) and 1.8-cineole (15.7%). Volatile secondary metabolites of basil cultivated in vitro with CuSO₄ were easily isolated and rapidly obtained. The results of this study demonstrate the feasibility and potential of using copper treatments to reduce the impact of seasonality on essential oil production.     

Partial interfertility between independently originated populations of the neo-allopolyploid <Emphasis Type="Italic">Mimulus peregrinus</Emphasis>

The reduction in genetic diversity in polyploid lineages, formed from whole-genome duplication of a few individuals, can affect their long-term evolutionary potential. Because most polyploids originate multiple times, secondary contact and gene exchange among independently formed polyploids can create novel genetic combinations and reduce the severity of genetic bottlenecks. However, independently originated polyploids may be reproductively isolated from each other due to genetic and chromosomal differences predating the polyploidisation event, or evolving subsequently in the dynamic genomes of young polyploid populations. Here we conducted experimental crosses to investigate the phenotype and interfertility between two independently originated populations of the allopolyploid Mimulus peregrinus (Phrymaceae). We found that individuals from the two populations are phenotypically distinct, but that inter- and intrapopulation crosses are not statistically different. Interpopulation crosses produce viable and fertile offspring, although our results suggest the existence of partial reproductive barriers in the form of reduced pollen viability. We found no difference in pollen viability between F1 and F2 generations. In contrast, we detected a reduction in floral and vegetative size, and in the proportion of plants that flowered, between F1 and F2 generations for both intra- and interpopulation crosses. Together, our results indicate that populations of independent origin can partially exchange genes, producing variable offspring, and that the phenotype of M. peregrinus may be unstable in the early generations. Natural selection on genetically based variation may be required for the evolution of more stable and fertile individuals of this nascent allopolyploid.     

The expanding phenotypic spectrum of female <Emphasis Type="Italic">SLC9A6</Emphasis> mutation carriers: a case series and review of the literature

Christianson syndrome (OMIM 300243), caused by mutations in the X-linked SLC9A6 gene, is characterized by severe global developmental delay and intellectual disability, developmental regression, epilepsy, microcephaly and impaired ocular movements. It shares many common features with Angelman syndrome. Carrier females have been described as having learning difficulties with mild to moderate intellectual disability, behavioural issues and psychiatric illnesses. There is little literature on the carrier female phenotype of Christianson syndrome. We describe a large extended family with three affected males, four carrier females, one presumed carrier female and one obligate carrier female with a c.190G>T, p.E64X mutation known to cause a premature stop codon in SLC9A6. We characterize and expand the clinical phenotype of female SLC9A6 mutation carriers by comparing our described family with female carriers previously discussed in the literature. In particular, we highlight the neurodevelopmental and psychiatric phenotypes observed in our family and previous reports.     

Hyperthermia of male <Emphasis Type="Italic">Drosophila melanogaster</Emphasis> meiocytes induces abnormalities in both paternal and maternal sex chromosome sets of the offspring

Nondisjunction and loss of sex chromosomes caused by exposure of male Drosophila melanogaster to heat shock (HS) (37°C for 1 h) has been studied to determine the role of mutation l(1)ts403 (sbr ¹⁰) in the control of chromosome segregation during cell division. Hyperthermia of males at the pupal stage has been demonstrated to increase the number of offspring with abnormalities of not only paternal, but also maternal sex chromosome sets. According to the criterion used, there is a temperature-sensitive period of spermatogenesis, which presumably coincides with meiosis. Phenotypes of some individuals correspond to the presence of two sex chromosomes of obtained from the same parent. The frequency of abnormal chromosome sets in the off-spring of male carriers of the sbr ¹⁰ mutation is about two times higher than in the offspring of males without this mutation.     

Effect of Gonadotropic Hormones on Stress Resistance of <Emphasis Type="Italic">Drosophila melanogaster</Emphasis> Females Infected with Different <Emphasis Type="Italic">Wolbachia pipientis</Emphasis> Genotypes

The effect of gonadotropic hormones (juvenile (JH) and 20-hydroxyecdysone (20E)) on heat stress resistance was for the first time studied in wild type D. melanogaster line females infected with different genotypes of the Wolbachia pipientis alpha-proteobacterium. It was found that an experimental increase in JH level induces a decrease in the heat stress resistance, while an increase in 20E level induces its increase in sixday females both uninfected with the Wolbachia and infected with different bacterium strains (wMelCS, wMelPop, and wMel). However, the intensity of response differs: a decrease in the survival with an increase in JH level and its increase with an increase in 20E level are more pronounced in females infected with pathogenic wMelPop strain and less pronounced in females infected with the wMelCS genotype than in uninfected females and females infected with the wMel genotype. Data obtained suggest that the wMelCS genotype induces a decrease and wMelPop induces an increase in the level of stress hormone (dopamine), since previously we demonstrated that an increase in the JH level in mature females increases the dopamine level, an increase in the 20E level decreases it, and an increase/decrease in the dopamine level, in turn, leads to a decrease/increase of the Drosophila female resistance to heat stress.     

The Role of Males in Host-Fruit Selection by Females of a Walnut Infesting Tephritid (Diptera) <Emphasis Type="Italic">Rhagoletis zoqui</Emphasis>

Rhagoletis zoqui Bush flies have a mating system in which males guard and defend walnut fruit-hosts from other males and mate, apparently without courtship, with females as they arrive to oviposit. Hypothetically, female selection of a particular fruit may be due to the quality of fruit for larval development (previously determined by guarding males), the quality of the male upon the fruit as a mate, or both, but this is not clear. We performed an experiment to determine if R. zoqui females or males select the fruit to oviposit or guard based on its quality for larval development (i.e., size, sugar-content [brix] or hardness), or following male-mediated cues such as chemical residues, related to prior fruit occupation by the male during guarding. Fruit choice by R. zoqui females and males were examined under semi-natural conditions on caged branches of English walnut trees, Juglans regia L., growing in the highlands of south-central Mexico. A single male or female was allowed to select a fruit and was then removed. An individual of the opposite sex was then introduced to the same branch and presented with the opportunity to choose among the same array of hosts. The pattern of fruit choice was consistent, with female choice on the basis of male presence, suggesting that males left a chemical cue that persisted in their absence. No fruit quality differences were detected between selected and non-selected fruit. Fruit features selected by females and males matched almost exactly, although males rarely select the same fruit as females. We conclude that females preferentially selected fruit previously occupied by males although additional studies are required to determine the cues used by R. zoqui for oviposition resource selection by both females and resource guarding males.     

Effects of male apparent length on female preference for absolute body size in <Emphasis Type="Italic">Xiphophorus helleri</Emphasis>

Female green swordtails (Xiphophorus helleri) prefer males of longer body and sword lengths, which may reflect perceptual constraints. Larger males project a larger image onto the female’s retina at a given viewing distance, which may elicit greater stimulation of the visual system and a stronger behavioral response. This study investigates the effects of male apparent size, as affected by proximity and sword length, on female preference for absolute body size in X. helleri. Females were presented pairs of dummy males in ten treatments organized into six categories: (1) the Actual Length Control where identically sized males were held at different viewing distances from the female; (2) the Sword Compensation Treatment in which viewing distance and apparent length (body + sword) were held constant, pairing sworded with swordless dummies of equal total length; (3) the Body Length Preference Treatment where male distance from the female was held constant, while varying body size; (4) the Apparent (Sword) Length Preference Treatments where male distance from the female was held constant, while varying sword length; (5) the Apparent Length Controls where body length, sword length, and viewing distances varied while holding apparent length constant; and (6) the Experimental Treatment in which the smaller-sworded male of the pair appeared larger. In each of the Actual Length Control, Body, and Sword Length Treatments, females preferred the closer, larger-bodied, and longer-sworded males, respectively. However, females exhibited preferences in neither any of the Apparent Size Control treatments nor any of the Sword Compensation Treatment. Additionally, females in the Experimental Treatment preferred the apparently longer-sworded dummy to the male whose sword was actually longer. These results suggest that female preference for male body and sword length is based on the male’s apparent rather than actual size.