Identification, sequence characteristics and expression analyses of four spore wall protein genes of Enterocytozoon hepatopenaei (EHP) in Litopenaeus vannamei.
Enterocytozoon hepatopenaei (EHP) is a newly emerged Microsporidian parasite that causes retarded growth of shrimp, which severely affects the normal development of shrimp industry. By now the mechanism that how this pathogen infects the shrimp has remained unclear, which severely impairs the effectiveness of the prevention and control of EHP. Some spore wall proteins (SWPs) of Microsporidia, as the major structure components, appear to be involved in the invasions in certain hosts. Therefore, identification and characterization of EHP SWPs are of great significance to the study of pathogenic biology and infection mechanism of EHP mediated by SWPs, which would facilitate the control of this pathogen. However, the reports on the EHP SWPs are few, and the potential functions of these molecules are largely unknown. In order to understand the biological characteristics and infection mechanism of local EHP in Shanghai, fanned shrimp (Litopenaeus vannamei) in the suburban farm of Shanghai confirmed to be infected by EHP were sampled to the following assays. The data from transcriptome sequencing with the hepatopancreas of EHP-infected shrimp revealed that four putative SWP-like protein genes were found and they were designated as EhEnP1, EhSWP7, EhSWP12, and EhSWP26. Sequence similarity analyses revealed that the amino acid sequences of these four molecules were identical with the ones reported in Thailand, which were obtained from the data of the genome sequence of EHP. Then the corresponding DNA sequences of these four SWP genes were cloned and sequenced. The results showed that the cDNA sequences of four SWP genes contained non-coding sequences which were the same as their respective DNA sequences. These results revealed that these four SWP genes had no introns. We also found that only EhSWP7 of these four proteins had a putative signal peptide and a functional domain MICSWaP was found in EhSWP26. Quantitative real-time PCR (qRT-PCR) was performed to analyze the expression levels. All four SWP genes expressed the highest in hepatopancreas, moderately in intestine and stomach but very low in gills. We further compared the four gene expression levels in hepatopancreas and found that the transcripts of EhSWP12 was significantly higher than other three genes, 1 implying that EhSWP12 might be a major structure protein in the sp re wall. This study provides new data on the study of EHP pathogenic biology and its invading mechanisms.