RESUMO
Previous work on Drosophila santomea suggested that its absence of abdominal pigmentation, compared to the other darkly pigmented species, is based on mutations in the cis-regulatory region of tan, inactivating the expression of that gene in the abdomen of D. santomea males and females. Our discovery that D. santomea males can produce viable hybrids when mated to D. melanogaster females enables us to use the armamentarium of genetic tools in the latter species to study the genetic basis of this interspecific difference in pigmentation. Hybridization tests using D. melanogaster deficiencies that include tan show no evidence that this locus is involved in the lighter pigmentation of D. santomea females; rather, the pigmentation difference appears to involve at least four other loci in the region. Earlier results implicating tan may have been based on a type of transgenic analysis that can give misleading results about the genes involved in an evolutionary change.
Assuntos
Proteínas Cromossômicas não Histona/genética , Proteínas de Ligação a DNA/genética , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Drosophila/genética , Pigmentação/genética , Animais , Quimera , Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Feminino , MasculinoRESUMO
Multicellular eukaryotic organisms are attacked by numerous parasites from diverse phyla, often simultaneously or sequentially. An outstanding question in these interactions is how hosts integrate signals induced by the attack of different parasites. We used a model system comprised of the plant host Arabidopsis thaliana, the hemibiotrophic bacterial phytopathogen Pseudomonas syringae, and herbivorous larvae of the moth Trichoplusia ni (cabbage looper) to characterize mechanisms involved in systemic-induced susceptibility (SIS) to T. ni herbivory caused by prior infection by virulent P. syringae. We uncovered a complex multilayered induction mechanism for SIS to herbivory. In this mechanism, antiherbivore defenses that depend on signaling via (1) the jasmonic acid-isoleucine conjugate (JA-Ile) and (2) other octadecanoids are suppressed by microbe-associated molecular pattern-triggered salicylic acid (SA) signaling and infection-triggered ethylene signaling, respectively. SIS to herbivory is, in turn, counteracted by a combination of the bacterial JA-Ile mimic coronatine and type III virulence-associated effectors. Our results show that SIS to herbivory involves more than antagonistic signaling between SA and JA-Ile and provide insight into the unexpectedly complex mechanisms behind a seemingly simple trade-off in plant defense against multiple enemies.
Assuntos
Arabidopsis/metabolismo , Arabidopsis/microbiologia , Etilenos/metabolismo , Herbivoria , Animais , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Hidrolases de Éster Carboxílico/genética , Hidrolases de Éster Carboxílico/metabolismo , Ciclopentanos/metabolismo , Regulação da Expressão Gênica de Plantas , Isoleucina/metabolismo , Mariposas , Mutação , Oxilipinas/metabolismo , Folhas de Planta , Pseudomonas syringae/patogenicidade , Ácido Salicílico/metabolismo , Transdução de SinaisRESUMO
Broadly applicable polymorphic genetic markers are essential tools for population genetics, and different types of markers have been developed for this purpose. Microsatellites have been employed as particularly polymorphic markers for over 20 years. However, PCR primers for microsatellite loci are often not useful outside the species for which they were designed. This implies that a new set of loci has to be identified and primers developed for every new study species. To overcome this constraint, we identified 45 conserved microsatellite loci based on the eight currently available ant genomes and designed primers for PCR amplification. Among these loci, we chose 24 for in-depth study in six species covering six different ant subfamilies. On average, 11.16 of these 24 loci were polymorphic and in Hardy-Weinberg equilibrium in any given species. The average number of alleles for these polymorphic loci within single populations of the different species was 4.59. This set of genetic markers will thus be useful for population genetic and colony pedigree studies across a wide range of ant species, supplementing the markers available for previously studied species and greatly facilitating the study of the many ant species lacking genetic markers. Our study shows that it is possible to develop microsatellite loci that are both conserved over a broad range of taxa, yet polymorphic within species. This should encourage researchers to develop similar tools for other large taxonomic groups.
Assuntos
Formigas/genética , Loci Gênicos , Repetições de Microssatélites/genética , Linhagem , Alelos , Animais , Primers do DNA/genética , Marcadores Genéticos , Genética Populacional , Genótipo , Especificidade da EspécieRESUMO
Hybrids between species are often sterile or inviable because the long-diverged genomes of their parents cause developmental problems when they come together in a single individual. According to the Dobzhansky-Muller (DM) model, the number of genes involved in these "intrinsic postzygotic incompatibilities" should increase faster than linearly with the divergence time between species. This straightforward prediction of the DM model has remained contentious owing to a lack of explicit tests. Examining two pairs of Drosophila species, we show that the number of genes involved in postzygotic isolation increases at least as fast as the square of the number of substitutions (an index of divergence time) between species. This observation verifies a key prediction of the DM model.