Chimerical nature of the ribosomal RNA gene of a Nosema species

Taxonomic resolution of the Nosema/Vairimorpha clade has been augmented with DNA sequences of the small subunit (SSU) and large subunit (LSU) ribosomal RNA (rRNA) and the arrangement of SSU and LSU. Based on the two characteristics, the clade is largely divided into two, i.e. ‘true’ Nosema sub-group and non-‘true’ Nosema sub-group within the clade. Our study shows that a novel Nosema species isolated from Pieris rapae has mixed characteristics of the ‘true’ and non-‘true’ Nosema sub-group based on the topology of SSU and LSU sequences. To our knowledge, this may be the first case of the incongruent phylogenetic placement of SSU and LSU in the Nosema/Vairimorpha clade. Additionally, the length of internal transcribed spacer (ITS) can be a diagnostic tool to distinguish ‘true’ Nosema from non-’true’ Nosema in the Nosema/Vairimorpha clade based on its nucleotide length as reported before.

Graphical abstractNosema C01 isolate from Pieris rapae shows chimerical nature in its small subunit (SSU) and large subunit (LSU).Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The Nosema isolate C01 shows mixed characteristics of ‘true’ and non-‘true’ Nosema based on its ribosomal RNA genes topologies. ► SSU sequences of the ‘true’ Nosema group and that of the ‘non-true’ Nosema group are under different selection pressure. ► The length of the ITS can be used as a diagnostic tool.