Multiple paternity and mate competition in non-selfing,monogamous, egg-trading hermaphrodites

In animals in which the two sexes invest relatively similar amounts of resources in their young, the number of mates is expected to affect male and female reproductive success similarly and gender conflicts on the number of mates may not arise. Correspondingly, in non-selfing, simultaneous hermaphrodites with long-term monogamy, the two partners are expected to alternate repeatedly their sexual roles and invest similarly in their offspring. Therefore, the gender conflict on the number of mating partners should not arise. However, when >2 conspecifics are present, hermaphrodites are known to plastically adjust their behavior and sex allocation and compete for mating repeatedly in the male role. We tested whether this leads to multiple paternities of single egg clutches in experimental replicates of small and large groups of non-selfing, egg-trading, behaviorally monogamous polychaete worms (Ophryotrocha diadema) by using neutral genetic markers to estimate paternity. Multiply fertilized egg cocoons were common in these worms; two or more individuals succeeded in fertilizing the same egg cocoon and mate competition increased with group size. Multiply fertilized egg cocoons had a higher proportion of eggs developing into mature worms than singly fertilized egg cocoons. Possibly singly fertilized cocoons had a lower fertilization rate owing to low sperm counts and aflagellate sperm.     

Cytogenetic studies in Eigenmannia virescens (Sternopygidae, Gymnotiformes) and new inferences on the origin of sex chromosomes in the Eigenmannia genus

Background

Previous studies suggested that multiple domestication events in South and South-East Asia (Yunnan and surrounding areas) and India have led to the genesis of modern domestic chickens. Ha Giang province is a northern Vietnamese region, where local chickens, such as the H'mong breed, and wild junglefowl coexist. The assumption was made that hybridisation between wild junglefowl and Ha Giang chickens may have occurred and led to the high genetic diversity previously observed. The objectives of this study were i) to clarify the genetic structure of the chicken population within the Ha Giang province and ii) to give evidence of admixture with G. gallus. A large survey of the molecular polymorphism for 18 microsatellite markers was conducted on 1082 chickens from 30 communes of the Ha Giang province (HG chickens). This dataset was combined with a previous dataset of Asian breeds, commercial lines and samples of Red junglefowl from Thailand and Vietnam (Ha Noï). Measurements of genetic diversity were estimated both within-population and between populations, and a step-by-step Bayesian approach was performed on the global data set.

Results

The highest value for expected heterozygosity (> 0.60) was found in HG chickens and in the wild junglefowl populations from Thailand. HG chickens exhibited the highest allelic richness (mean A = 2.9). No significant genetic subdivisions of the chicken population within the Ha Giang province were found. As compared to other breeds, HG chickens clustered with wild populations. Furthermore, the neighbornet tree and the Bayesian clustering analysis showed that chickens from 4 communes were closely related to the wild ones and showed an admixture pattern.

Conclusion

In the absence of any population structuring within the province, the H'mong chicken, identified from its black phenotype, shared a common gene pool with other chickens from the Ha Giang population. The large number of alleles shared exclusively between Ha Giang chickens and junglefowl, as well as the results of a Bayesian clustering analysis, suggest that gene flow has been taking place from junglefowl to Ha Giang chickens.     

The characterization of the soybean polygalacturonase-inhibiting proteins (Pgip) gene family reveals that a single member is responsible for the activity detected in soybean tissues

Polygalacturonase-inhibiting proteins (PGIPs) are leucine-rich repeat (LRR) proteins that inhibit fungal endopolygalacturonases (PGs). They are encoded by multigene families whose members show functional redundancy and subfunctionalization for recognition of fungal PGs. In order to expand the information on the structure and functional features of legume PGIP, we have isolated and characterized four members of the soybean Pgip gene family and determined the properties of the encoded protein products. Sequence analysis showed that these genes form two clusters: one cluster of about 5 kbp containing Gmpgip1 and Gmpgip2, and the other containing Gmpgip3 and Gmpgip4 within a 60 kb fragment of a separate BAC clone. Sequence diversification of the four members resides mainly in the xxLxLxx region that includes residues forming the β-sheet B1. When compared with other legume Pgip genes, Gmpgip3 groups with the bean genes Pvpgip1 and Pvpgip2, suggesting that these genes are closer to the ancestral gene. At the protein level, only GmPGIP3 shows the capability to inhibit fungal PGs. The spectrum of inhibition of GmPGIP3 against eight different fungal PGs mirrors that of the PGIP purified from soybean tissues and is similar to that of the bean PvPGIP2, one of the most efficient inhibitors so far characterized. We also report that the four Gmpgip genes are differentially regulated after wounding or during infection with the fungal pathogen Sclerotinia sclerotiorum. Following fungal infection Gmpgip3 is up regulated promptly, while Gmpgip2 is delayed.     

Somatic breakpoints,distribution of repetitive DNA and non-LTR retrotransposon insertion sites in the chromosomes of <Emphasis Type="Italic">Chironomus piger</Emphasis> Strenzke (Diptera,Chironomidae)

Structural aberrations, their frequency and distribution as well as distribution of the tandem repetitive minisatellite DNA clusters of Alu and Hinf elements and two retroelements, the LINE NLRCth1 and the SINE CTRT1, were analyzed in the genome of the chironomid C. piger Strenzke larvae from a Bulgarian population. A consistent somatic variability in the structure of the polytene chromosomes was detected, showing that the C. piger genome is more actively rearranging than supposed before. Breakpoints were concentrated in proximal parts of chromosomes significantly more often than in distal parts. By FISH analysis we could detect only one locus containing Alu elements and 38 Hinf cluster loci which appear to be dispersed equally all over the chromosomes. The retrotransposons NLRCth1 and CTRT1 are present only in a few loci, but highly variant among different individuals. The mean number of NLRCth1 sites per individual was 18.4 ± 2.09 and of CTRT1 was 54.8 ± 8.42. A third of breakpoint locations were close to or coincide with a locus occupied by a retroelement (either NLRCth1 or CTRT1). Nineteen percent of breakpoints coincided with Hinf repetitive DNA elements. Some breakpoints were identical in the two sibling species C. piger and C. riparius Meigen (syn.: C. thummi thummi) and are considered as conserved hot spots of chromosome breakage.     

Insertional variability of four transposable elements and population structure of the midge Chironomus riparius (Diptera)

The dipteran Chironomus riparius is found across the entire Palearctic region; its larvae are among the most abundant macroinvertebrates inhabiting inland waterbodies. Chironomid larvae have been extensively used in ecotoxicological and cytogenetic research, but relatively little is known on the population structure of this species. Transposable elements (TEs) are DNA sequences that are capable of autonomous replication; the number and genomic location of TE insertions varies across individuals; this variability is increasingly being used in population studies. Several TEs had been characterized in Chironomids; this enabled the analysis of insertional variability of four different TEs in six natural populations of C. riparius from Italy, Bulgaria and Russia using a PCR-based method, transposon insertion display (TID). The method allows to obtain dominant markers, similar to AFLP. In all populations, TE insertions showed high individual polymorphism, while median copy numbers of the same TEs did not vary between populations. Analysis of molecular variance (AMOVA) detected significant differentiation between populations for three of the TEs; although no correlation between genetic and geographic distances was found, the corresponding population structures were found to be significantly correlated and indicate a degree of isolation by distance. TEs belonging to different classes have different mechanisms of replication, resulting in different transposition rates of mobilization; the finding of mostly concordant population structuring for three of the TEs indicates that population dynamics contributed significantly in shaping the detected insertional polymorphism.     

DAT1 VNTR polymorphisms in a European and an African population: identification of a new allele

Polymorphism frequencies of the dopamine transporter gene (DAT1) hypervariable region have been analyzed in a sample of Italian and Ivory Coast individuals. The 3' untranslated region (UTR) of DAT1 includes a variable number of tandem repeats (VNTR) of a 40-bp monomer, ranging from 3 to 13 repeats in Caucasian and African populations. In our sample we found alleles with 3 to 16 repeats, and the most common alleles were the 10-repeat (DAT1*10) and the 9-repeat (DAT1*9) alleles. We also found two rare alleles in the Italian population and four in the Ivory Coast population. For the first time the new allele DAT1*16 is described in the Ivorians. The Ivory Coast population was not in Hardy-Weinberg equilibrium for the DAT1 locus because of a deficit of heterozygote genotypes. The observed heterozygosity of the Ivorian population was half that of the Italians. The lower observed heterozygosity and deviation from Hardy-Weinberg equilibrium could be the result of microevolutionary trends, such as genetic drift and/or inbreeding, acting on the relatively small and isolated population sampled for this study, although some sort of selective pressures acting against the shorter alleles cannot be excluded. This evidence, in association with the reduced polymorphism shown by the DAT1 VNTR compared to other VNTRs, seems to indicate that the DAT1 locus may be under some selective pressure.     

Pervasive Natural Selection in the Drosophila Genome?

Over the past four decades, the predominant view of molecular evolution saw little connection between natural selection and genome evolution, assuming that the functionally constrained fraction of the genome is relatively small and that adaptation is sufficiently infrequent to play little role in shaping patterns of variation within and even between species. Recent evidence from Drosophila, reviewed here, suggests that this view may be invalid. Analyses of genetic variation within and between species reveal that much of the Drosophila genome is under purifying selection, and thus of functional importance, and that a large fraction of coding and noncoding differences between species are adaptive. The findings further indicate that, in Drosophila, adaptations may be both common and strong enough that the fate of neutral mutations depends on their chance linkage to adaptive mutations as much as on the vagaries of genetic drift. The emerging evidence has implications for a wide variety of fields, from conservation genetics to bioinformatics, and presents challenges to modelers and experimentalists alike.     

Inhibition of adamalysin II and MMPs by phosphonate analogues of snake venom peptides

Phosphonate analogues of the peptidomimetic N-(Furan-2-yl)carbonyl-Leu-Trp-OH were prepared with the goal of evaluating the effect of phosphonate for carboxylate replacement on binding with snake venom metalloproteinases and MMPs. N-(Furan-2-yl)carbonyl-Leu-L-Trp(P)-(OH)2 showed a 75-fold increase of the inhibiting activity against adamalysin II, a snake venom metalloproteinase structurally related to MMPs and TACE. Both the phosphonate and carboxylate peptidomimetics fit into the active site adopting a retrobinding mode and provide the structural base for a new class of metalloproteinases inhibitors.