Genetic diversity, demographic history and neo-sex chromosomes in the Critically Endangered Raso lark
Ontology highlight
ABSTRACT: Analysis of study genetic diversity, demography and neo-sex chromosomes in the Raso lark Alauda razae and its relatives the Eurasian Skylark A. arvensis, Oriental skylark A. gulgula and crested lark Galerida cristata, based on RAD-seq analysis.
Project description:Small effective population sizes could expose island species to inbreeding and loss of genetic variation. Here, we investigate factors shaping genetic diversity in the Raso lark, which has been restricted to a single islet for approximately 500 years, with a population size of a few hundred. We assembled a reference genome for the related Eurasian skylark and then assessed diversity and demographic history using RAD-seq data (75 samples from Raso larks and two related mainland species). We first identify broad tracts of suppressed recombination in females, indicating enlarged neo-sex chromosomes. We then show that genetic diversity across autosomes in the Raso lark is lower than in its mainland relatives, but inconsistent with long-term persistence at its current population size. Finally, we find that genetic signatures of the recent population contraction are overshadowed by an ancient expansion and persistence of a very large population until the human settlement of Cape Verde. Our findings show how genome-wide approaches to study endangered species can help avoid confounding effects of genome architecture on diversity estimates, and how present-day diversity can be shaped by ancient demographic events.
Project description:Circadian behaviors are regulated by intrinsic biological clocks consisting of central molecular oscillators and output pathways. Despite significant progress in elucidating the central timekeeping mechanisms, the molecular pathways coupling the circadian pacemaker to overt rhythmic behavior and physiology remain elusive. The Drosophila LARK RNA-binding protein is a candidate for such a coupling factor. Previous research indicates that LARK functions downstream of the clock to mediate behavioral outputs. To better understand the roles of LARK in the Drosophila circadian system, we sought to identify RNA molecules associated with LARK in vivo, using a novel strategy that involves capturing the RNA ligands by immunoprecipitation, visualizing the captured RNAs using whole gene microarrays, and identifying functionally relevant targets through genetic screens. Keywords: Association with RNA-binding protein
Project description:Circadian behaviors are regulated by intrinsic biological clocks consisting of central molecular oscillators and output pathways. Despite significant progress in elucidating the central timekeeping mechanisms, the molecular pathways coupling the circadian pacemaker to overt rhythmic behavior and physiology remain elusive. The Drosophila LARK RNA-binding protein is a candidate for such a coupling factor. Previous research indicates that LARK functions downstream of the clock to mediate behavioral outputs. To better understand the roles of LARK in the Drosophila circadian system, we sought to identify RNA molecules associated with LARK in vivo, using a novel strategy that involves capturing the RNA ligands by immunoprecipitation, visualizing the captured RNAs using whole gene microarrays, and identifying functionally relevant targets through genetic screens. Experiment Overall Design: LARK-containing ribonucleoprotein complexes (LARK-RNPs) were precipitated from lysates of hand-dissected pharate adult brains using an affinity-purified anti-LARK antibody (around 1000 brains were used per immunoprecipitation experiment). A portion of each lysate was saved prior to immunoprecipitations (IPs) in order to measure the relative abundance of transcripts in a total RNA sample. RNAs extracted from the LARK-RNP and total RNA samples were labeled and hybridized to Drosophila whole-genome gene microarrays; signal intensities for individual genes were compared between samples to identify those RNAs that were enriched by immunoprecipitation (relative to their abundances in total RNA). RNAs that were selectively enriched in the LARK-RNP samples were considered to be potential targets of the RNA-binding protein. Experiment Overall Design: Due to the difficulty to dissect large amount of fly brains, only two such immunoprecipitation experiments were performed, each generating an IP RNA sample and a total RNA (control) sample. The amount of RNAs obtained from IP is very small thus only one array is used for each sample - i.e. there are only biological replicates and no technical replicate.
Project description:The goal of this study is to identify, in the head of adult flies, mRNA species whose expresson level are altered by overexpression of the Drosophila RNA-binding protein LARK in CNS neurons. Keywords: genetic modification, gene experssion profile
Project description:The goal of this study is to identify, in the head of adult flies, mRNA species whose expresson level are altered by overexpression of the Drosophila RNA-binding protein LARK in CNS neurons. Experiment Overall Design: RNA samples from adult head of the LARK overexpression flies (elav-gal4; uas-lark/+) and control flies were compared. One total RNA sample was isolated from each genotype, of which three technical replicates (repeating the labeling and hybridization processes) were generated, respectively.