Long-term experimental evolution reveals purifying selection on piRNA-mediated control of transposable element expression

BMC Biology

Vaishali Katju¹  Ulfar Bergthorsson¹  Anke Konrad²  Caroline J. Sheeba³  Peter Sarkies³  Tony Belicard³  Toni Beltran⁴ 

[1] Department of Veterinary Integrative Biosciences, Texas A&M University, 77845, College Station, TX, USA;Department of Veterinary Integrative Biosciences, Texas A&M University, 77845, College Station, TX, USA;Present Address: Intituto Gulbenkian de Ciencia, Rua da Quinta Grande, 6, 2780-156, Oeiras, Portugal;MRC London Institute of Medical Sciences, Du Cane Road, W12 0NN, London, UK;Institute of Clinical Sciences, Imperial College London, Du Cane Road, W12 0NN, London, UK;MRC London Institute of Medical Sciences, Du Cane Road, W12 0NN, London, UK;Institute of Clinical Sciences, Imperial College London, Du Cane Road, W12 0NN, London, UK;Present Address: Centre for Genomic Regulation, PRBB Building, 08003, Barcelona, Spain;

关键词: C. elegans;    Experimental evolution;    Transposable elements;    Epigenetics;    Small RNAs;    piRNAs;    Chromatin;   

DOI  :  10.1186/s12915-020-00897-y

来源: Springer

【 摘 要 】

BackgroundTransposable elements (TEs) are an almost universal constituent of eukaryotic genomes. In animals, Piwi-interacting small RNAs (piRNAs) and repressive chromatin often play crucial roles in preventing TE transcription and thus restricting TE activity. Nevertheless, TE content varies widely across eukaryotes and the dynamics of TE activity and TE silencing across evolutionary time is poorly understood.ResultsHere, we used experimentally evolved populations of C. elegans to study the dynamics of TE expression over 409 generations. The experimental populations were evolved at population sizes of 1, 10 and 100 individuals to manipulate the efficiency of natural selection versus genetic drift. We demonstrate increased TE expression relative to the ancestral population, with the largest increases occurring in the smallest populations. We show that the transcriptional activation of TEs within active regions of the genome is associated with failure of piRNA-mediated silencing, whilst desilenced TEs in repressed chromatin domains retain small RNAs. Additionally, we find that the sequence context of the surrounding region influences the propensity of TEs to lose silencing through failure of small RNA-mediated silencing.ConclusionsOur results show that natural selection in C. elegans is responsible for maintaining low levels of TE expression, and provide new insights into the epigenomic features responsible.

【 授权许可】

CC BY