DNA and RNA-dependent polymerization in editing of Bombyx chemosensory protein (CSP) gene family

The relationship between the diversity of chemosensory proteins (CSPs) and their limited gene repertoire is of great interest. We have previously demonstrated that mRNA editing is responsible for this diversity. In this report, we describe hypotheses we have developed from phylogenetic analyses of CSP genes and RNA variants of the silkworm moth, Bombyx mori. Our analysis is based on previously published DNA/RNA/peptide sequencing data of the different variants from different tissues (Xuan et al., 2014, Xuan et al., 2016). We find and describe conventional A-to-I RNA editing, and C-to-U/U-to-C editing events in different CSP variants and pinpoint loci we believe encode the ADAR and ADAT enzymes and variants thereof that are responsible for these events. We also describe several non-conventional editing events including G-to-I and C-to-I, suggesting the existence of a multitude of mutation mechanisms in insects as found in microbes, viruses and plants. In particular, our phylogenetic analysis indicates that some mRNA sequences are more closely related to edited mRNA than to the gene sequence and shows evidence of tissue-specific DNA-dependent (Dd) or RNA-dependent (Rd) mutations depending on the gene. These descriptive findings in the silkworm are useful for molecular evolution of Dd-and Rd-RNA polymerases in relation with a specific gene family, as well as evolutionary biology and adaptation of RNA, cell, tissue or organism to new environment.