Project description:Two introgression strains (ZZY10307 and ZZY10330) of C. briggsae onto the X chromosome of C. nigoni results in male sterility. In order to determine the cause, we sequenced the mRNAs from young adult males from these two strains, and compared to fertile males of the two parent species (AF16 and JU1421). Two wild-type female samples were also included as platform QC.
2016-05-11 | GSE76306 | GEO
Project description:Oxford Nanopore sequencing of targeted recombinants between C. briggsae and C. nigoni
Project description:Piwi proteins and Piwi-interacting RNAs (piRNAs) are best known for their roles in suppressing transposons and promoting fertility. Yet piRNA biogenesis and its mechanisms of action differ widely between distantly related species. To better understand the evolution of piRNAs, we characterized the piRNA pathway in C. briggsae, a sibling species of the model organism C. elegans. Our analyses define 25,883 piRNA producing-loci in C. briggsae. piRNA sequences in C. briggsae are extremely divergent from their counterparts in C. elegans, yet both species adopt similar genomic organization and transcription program that drive piRNA expression. By examining production of Piwi-dependent secondary small RNAs, we identified a set of protein-coding genes that are evolutionarily conserved piRNA targets. In contrast to C. elegans, small RNAs mapped to ribosomal RNAs or histone transcripts are not hyper-accumulated in C. briggsae. Instead, we found that fewer introns in transcripts are associated with hyper-accumulation of small RNAs. Together our work highlights evolutionary conservation and divergence of the nematode piRNA pathway and provides insights into its role in endogenous gene regulation.
Project description:Geographically distinct populations can adapt to the temperature conditions of their local environment, leading to temperature-dependent fitness differences between populations. Consistent with local adaptation, phylogeographically distinct Caenorhabditis briggsae nematodes show distinct fitness responses to temperature. The genetic mechanisms underlying local adaptation, however, remain unresolved. To investigate the potential role of small noncoding RNAs in genotype-specific responses to temperature, we quantified small RNA expression using high-throughput sequencing of C. briggsae nematodes from tropical and temperate strain genotypes reared under three temperature conditions (14˚, 20˚, 30˚C). Strains representing both tropical and temperate regions showed significantly lower expression of PIWI-interacting RNAs (piRNAs) at high temperatures, primarily mapping to a large ~7 Mb long piRNA cluster on chromosome IV. We also documented decreased expression of 22G-RNAs antisense to protein-coding genes and other genomic features at high rearing temperatures for the thermally-intolerant temperate strain genotype, but not for the tropical strain genotype. Reduced 22G-RNA expression was widespread along chromosomes and among feature types, indicative of a genome-wide response. Targets of the EGO-1/CSR-1 22G-RNA pathway were most strongly impacted compared to other 22G-RNA pathways, implicating the CSR-1 Argonaute and its RNA-dependent RNA polymerase EGO-1 in the genotype-dependent modulation of C. briggsae 22G-RNAs under chronic thermal stress. Our work suggests that gene regulation via small RNAs may be an important contributor to the evolution of local adaptations.
