Lecture11.pdf - RESEARCH ARTICLE Bombyx mori histone...

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RESEARCH ARTICLE Bombyx mori histone methyltransferase BmAsh2 is essential for silkworm piRNA- mediated sex determination Zhiqian Li 1 , Lang You 1 , Dong Yan 1 , Anthony A. James 2 , Yongping Huang 1 , Anjiang Tan 1 * 1 CAS Key Laboratory of Insect Developmental and Evolutionary Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China, 2 Departments of Microbiology & Molecular Genetics and Molecular Biology & Biochemistry, University of California, Irvine, Irvine, California, United States of America * [email protected] Abstract Sex determination is a hierarchically-regulated process with high diversity in different organ- isms including insects. The W chromosome-derived Fem piRNA has been identified as the primary sex determination factor in the lepidopteran insect, Bombyx mori , revealing a dis- tinctive piRNA-mediated sex determination pathway. However, the comprehensive mecha- nism of silkworm sex determination is still poorly understood. We show here that the silkworm PIWI protein BmSiwi, but not BmAgo3, is essential for silkworm sex determination. CRISPR/Cas9-mediated depletion of BmSiwi results in developmental arrest in oogenesis and partial female sexual reversal, while BmAgo3 depletion only affects oogenesis. We identify three histone methyltransferases (HMTs) that are significantly down-regulated in BmSiwi mutant moths. Disruption one of these, BmAsh2 , causes dysregulation of piRNAs and transposable elements ( TEs ), supporting a role for it in the piRNA signaling pathway. More importantly, we find that BmAsh2 mutagenesis results in oogenesis arrest and partial female-to-male sexual reversal as well as dysregulation of the sex determination genes, Bmdsx and BmMasc . Mutagenesis of other two HMTs, BmSETD2 and BmEggless , does not affect piRNA-mediated sex determination. Histological analysis and immunoprecipita- tion results support a functional interaction between the BmAsh2 and BmSiwi proteins. Our data provide the first evidence that the HMT, BmAsh2, plays key roles in silkworm piRNA- mediated sex determination. Author summary Sex determination is an essential and universal process for metazoan reproduction and development. Insect sex determination is highly diverse, especially for the primary signal and transductory genes. Mechanism of sex determination in the model lepidopteran insect, Bombyx mori , is largely unknown, although a piRNA, named Fem , has been identi- fied recently as the initial factor. In the current report, we generate somatic mutants for the two silkworm piRNA-bound proteins, BmSiwi and BmAgo3 , and identify that the PLOS Genetics | https://doi.org/10.1371/journal.pgen.1007245 February 23, 2018 1 / 19 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Li Z, You L, Yan D, James AA, Huang Y, Tan A (2018) Bombyx mori histone methyltransferase BmAsh2 is essential for silkworm piRNA-mediated sex determination. PLoS Genet 14(2): e1007245. https://doi.org/10.1371/ journal.pgen.1007245 Editor: Gregory P. Copenhaver, The University of North Carolina at Chapel Hill, UNITED STATES
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