The characterization of cytoplasmic ribosomal protein genes in microsporidian Nosema bombycis Genome

Abstract

Microsporidia are obligate intracellular, eukaryotic parasites of medical and commercial importance, which can infect almost all animals including humans. However, their ribosomes are not of the 80S type as other eukaryotes, but like the prokaryotic 70S ribosome. In order to get the global composition of ribosomal protein genes of Nosema bombycis, the pathogen of Pébrine, and their comparative genomics’ characteristics, a genome-wide survey in N. bombycis genome was performed. From the results, we identified 130 CDSs corresponding to 73 ribosomal protein genes. Among them, three ribosomal protein genes (RPL19, RPS4 and RPS18) with short introns (23 or 24 bps) were verified by N. bombycis ESTs, and they have the same structure among microsporidia. The novel arrangements of ‘AAATTT-like signal – CCC/GGG-like motif – transcription start site’ are present in the upstream sequences of ribosomal protein genes, and several regulatory elements that may have synergy with introns of ribosomal protein genes for its high transcriptional frequency were detected too. 76.7% ribosomal protein genes of N. bombycis were located in syntenic blocks, indicating that their gene order was conserved among microsporidian species. And phylogenic trees show its ancient eukaryotic position too. The characterization of the total ribosomal proteins contributes a first step to ribosomal proteins’ transcription regulation, evolution of microsporidia.

Keywords: Microsporidian, ribosomal protein, Nosema bombycis, transcription regulation, evolution