Atypical somatic small RNAs in Anopheles
Small RNAs of the Piwi-interacting RNA class (piRNA) play a key role in controlling the activity of transposable elements (TEs) in the animal germ line. In some arthropod species, including mosquitoes, the vectors of malaria and other pathogens, the piRNA pathway is active not only in the gonads, where it controls TE activity, but also in somatic tissues, where its targets and functions are less clear. It is thought that the piRNA pathway in somatic tissues is involved in the antiviral response and the modulation of TE activity. Here, we studied the features of small RNA production in head and thorax somatic tissues of Anopheles coluzzii focusing on the small RNAs processed from protein-coding gene mRNAs. We revealed tissue and sex specificity in the production of small RNAs derived from the genic transcripts. Genic small RNAs of 24-30 nt in length are atypical RNAs that lack the hallmarks of piRNAs. The majority of these short RNAs are derived from mitochondrial and nuclear genes involved in energy metabolism. We discuss the peculiarities of the piRNA biogenesis in Anopheles species which may result in the production of genic small RNAs in the somatic tissues. Overall design: Deep-sequencing of small RNAs (18-32 nt) of Anopheles coluzzii somatic tissues and sexes.