Germline silencing of UASt depends on the piRNA pathway

Publication date: Available online 9 May 2018
Source:Journal of Genetics and Genomics
Author(s): Yi-Chun Huang, Henry Moreno, Sarayu Row, Dongyu Jia, Wu-Min Deng
One of the most extensively used techniques in Drosophila is the Gal4/UAS binary system, which allows tissue-specific misexpression or knockdown of specific genes of interest. The original UAS vector, UASt, can only be activated for transgene expression in somatic tissues but not in the germline cells (Brand and Perrimon, 1993). Here, we find that the piwi-interacting RNA (piRNA) pathway is involved in suppressing UASt expression in ovarian germline cells. Individually knocking down or mutating components of the piRNA biogenesis pathway (e.g., Piwi, AGO3, Aub, Spn-E, Su(var)2–10, Hsp83, and Vasa) resulted in the expression of the UASt-reporter (GFP or RFP) in the germline. An RNA-seq analysis of small RNAs revealed that the hsp70 promoter of UASt is targeted by piRNAs, and in the aub mutant ovary, the amount of piRNAs targeting the hsp70 promoter is reduced by around 40 folds. In contrast, the SV40 3′UTR of the UASt, which happens to be targeted by the nonsense-mediated RNA decay (NMD) pathway, is not responsible for germline UASt suppression, as UASt-reporters with NMD-insensitive 3′UTR fail to show germline expression. Taken together, our studies reveal a crucial role of the piRNA pathway, potentially via the suppression of the hsp70 promoter, in germline UASt silencing in Drosophila ovaries.



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