Effective population size of Anopheles funestus chromosomal forms in Burkina Faso

BACKGROUND: As Anopheles funestus is one of the principal Afro-tropical malaria vectors, a more complete understanding of its population structure is desirable. In West and Central Africa, An. funestus population structure is complicated by the coexistence of two assortatively mating chromosomal forms. Effective population size (N(e)) is a key parameter in understanding patterns and levels of intraspecific variation, as it reflects the role of genetic drift. Here, N(e )was estimated from both chromosomal forms, Kiribina and Folonzo, in Burkina Faso. METHODS: Short-term N(e )was estimated by evaluating variation at 16 microsatellite loci across temporal samples collected annually from 2000–2002. Estimates were based on standardized variance in allele frequencies or a maximum likelihood method. Long-term N(e )was estimated from genetic diversity estimates using mtDNA sequences and microsatellites. RESULTS: For both forms, short-term and long-term N(e )estimates were on the order of 10(3 )and 10(5), respectively. Long-term N(e )estimates were larger when based on loci from chromosome 3R (both inside and outside of inversions) than loci outside of this arm. CONCLUSION: N(e )values indicate that An. funestus is not subject to seasonal bottlenecks. Though not statistically different because of large and overlapping confidence intervals, short-term N(e )estimates were consistently smaller for Kiribina than Folonzo, possibly due to exploitation of different breeding sites: permanent for Folonzo and intermittent for Kiribina. The higher long-term N(e )estimates on 3R, the arm carrying the two inversions mainly responsible for defining the chromosomal forms, give natural selection broader scope and merit further study

Effective population size of Anopheles funestus chromosomal forms in Burkina Faso

Abstract Background As Anopheles funestus is one of the principal Afro-tropical malaria vectors, a more complete understanding of its population structure is desirable. In West and Central Africa, An. funestus population structure is complicated by the coexistence of two assortatively mating chromosomal forms. Effective population size (N e) is a key parameter in understanding patterns and levels of intraspecific variation, as it reflects the role of genetic drift. Here, N ewas estimated from both chromosomal forms, Kiribina and Folonzo, in Burkina Faso. Methods Short-term N ewas estimated by evaluating variation at 16 microsatellite loci across temporal samples collected annually from 2000–2002. Estimates were based on standardized variance in allele frequencies or a maximum likelihood method. Long-term N ewas estimated from genetic diversity estimates using mtDNA sequences and microsatellites. Results For both forms, short-term and long-term N eestimates were on the order of 103 and 105, respectively. Long-term N eestimates were larger when based on loci from chromosome 3R (both inside and outside of inversions) than loci outside of this arm. Conclusion Nevalues indicate that An. funestus is not subject to seasonal bottlenecks. Though not statistically different because of large and overlapping confidence intervals, short-term Neestimates were consistently smaller for Kiribina than Folonzo, possibly due to exploitation of different breeding sites: permanent for Folonzo and intermittent for Kiribina. The higher long-term Neestimates on 3R, the arm carrying the two inversions mainly responsible for defining the chromosomal forms, give natural selection broader scope and merit further study.http://deepblue.lib.umich.edu/bitstream/2027.42/112376/1/12936_2006_Article_293.pd

A Molecular Analysis of Mutations at the Complex dumpy Locus in Drosophila melanogaster

The Drosophila dumpy gene consists of seventy eight coding exons and encodes a huge extracellular matrix protein containing large numbers of epidermal growth factor-like (EGF) modules and a novel module called dumpy (DPY). A molecular analysis of forty five mutations in the dumpy gene of Drosophila melanogaster was carried out. Mutations in this gene affect three phenotypes: wing shape, thoracic cuticular defects, and lethality. Most of the mutations were chemically induced in a single dumpy allele and were analyzed using a nuclease that cleaves single base pair mismatches in reannealed duplexes followed by dHPLC. Additionally, several spontaneous mutations were analyzed. Virtually all of the chemically induced mutations, except for several in a single exon, either generate nonsense codons or lesions that result in downstream stop codons in the reading frame. The remaining chemically induced mutations remove splice sites in the nascent dumpy message. We propose that the vast majority of nonsense mutations that affect all three basic dumpy phenotypes are in constitutive exons, whereas nonsense mutants that remove only one or two of the basic functions are in alternatively spliced exons. Evolutionary comparisons of the dumpy gene from seven Drosophila species show strong conservation of the 59 ends of exons where mutants with partial dumpy function are found. In addition, reverse transcriptio

Divergence With Gene Flow in Anopheles funestus From the Sudan Savanna of Burkina Faso, West Africa

Anopheles funestus is a major vector of malaria across Africa. Understanding its complex and nonequilibrium population genetic structure is an important challenge that must be overcome before vector populations can be successfully perturbed for malaria control. Here we examine the role of chromosomal inversions in structuring genetic variation and facilitating divergence in Burkina Faso, West Africa, where two incipient species (chromosomal forms) of A. funestus, defined principally by rearrangements of chromosome 3R, have been hypothesized. Sampling across an ∼300-km east–west transect largely contained within the Sudan–Savanna ecoclimatic zone, we analyzed chromosomal inversions, 16 microsatellite loci distributed genomewide, and 834 bp of the mtDNA ND5 gene. Both molecular markers revealed high genetic diversity, nearly all of which was accounted for by within-population differences among individuals, owing to recent population expansion. Across the study area there was no correlation between genetic and geographic distance. Significant genetic differentiation found between chromosomal forms on the basis of microsatellites was not genomewide but could be explained by chromosome 3R alone on the basis of loci inside and near inversions. These data are not compatible with complete reproductive isolation but are consistent with differential introgression and sympatric divergence between the chromosomal forms, facilitated by chromosome 3R inversions

High Dietary Sugar Reshapes Sweet Taste to Promote Feeding Behavior in Drosophila melanogaster

Summary: Recent studies find that sugar tastes less intense to humans with obesity, but whether this sensory change is a cause or a consequence of obesity is unclear. To tackle this question, we study the effects of a high sugar diet on sweet taste sensation and feeding behavior in Drosophila melanogaster. On this diet, fruit flies have lower taste responses to sweet stimuli, overconsume food, and develop obesity. Excess dietary sugar, but not obesity or dietary sweetness alone, caused taste deficits and overeating via the cell-autonomous action of the sugar sensor O-linked N-Acetylglucosamine (O-GlcNAc) transferase (OGT) in the sweet-sensing neurons. Correcting taste deficits by manipulating the excitability of the sweet gustatory neurons or the levels of OGT protected animals from diet-induced obesity. Our work demonstrates that the reshaping of sweet taste sensation by excess dietary sugar drives obesity and highlights the role of glucose metabolism in neural activity and behavior. : May et al. discover that excess dietary sugar promotes overfeeding by dulling sweet taste sensation in Drosophila melanogaster. Deficits in taste function occur independently of obesity and, instead, develop because of higher glucose utilization inside the gustatory neurons. Correcting sweet taste function prevents overconsumption and obesity in animals fed a high sugar diet