Aquaculture 2022

February 28 - March 4, 2022

San Diego, California

EXPLORING PATHOGENICITY ATTENUATION OF THE INTRACELLULAR BACTERIUM Piscirickettsia salmonis THROUGH SMALL NON-CODING RNA

Yeny Leal*, Valentina Valenzuela-Muñoz, Cristian Gallardo-Escárate

 

Laboratory of Biotechnology and Genomic Aquatic, Interdisciplinary Center for Aquaculture Research (INCAR)

University of Concepción.

Concepción, Chile

*yleal@udec.cl

 



 Salmonid rickettsial septicemia (SRS) is one of the major diseases affecting  the salmon industry in Chile . The intracellular bacterium Piscirickettsia salmonis  is  the responsible pathogen of SRS  that  can infect multiple tissues in its host. New approaches for its control are  considered a significant challenge in the scientific community.  Advances in high-throughput sequencing technologies allow a better understanding of the transcriptomic responses of organisms in several biological scenarios, such as pathogen-host interaction.  In this sense,  miRNAs play an essential role in the transcriptomic response of Salmo salar during infection with P. salmonis , promoting a change in the diversity of miRNA families. Also, miRNAs co-modulate the transcriptional activity of their target genes, suggesting a putative function of non-coding RNAs in the immune response of salmon  infected with an intracellular pathogen .  This study aimed to identify candidates for small non-coding RNA (sRNA) involved in  the  pathogenesis process of  P. salmonis  during infection in S. salar and validate at a functional level the genomic modulation of these sRNA  at in vitro model of P. salmonis infection .

Transcriptome of  experimental infections with P. salmonis EM-90 wild and attenuated in Atlantic salmon was used for sRNA candidate selection .  First, putative sRNAs P. salmonis binding sites in up and down-regulated S. salar genes during infection were predicted using RNA22 version 2.0 software. Then, two sRNA were selected based on RNAseq analysis expression, synthesized as mimics (mir-222, mir 143-37), and co-transfected with  the GFP reporter gene in the salmon head kidney SHK-1 cell line . After 48h, the modified SHK-1 cells were infected with 1x106 CFU/mL P. salmonis. Cytotoxicity and cytopathic effects were monitored 24 hours after infection.

The experimental group transfected with mir-143- 37 showed  lower cytotoxicity  against infection with P. salmonis compared to the other groups tested (Table 1). Moreover ,  quantitative PCR analysis indicated regulation of transcription of  immune-related genes  in SHK-1 groups transfected with mimics. In addition , an increase in the relative expression of the E3 ubiquitin-protein ligase CBL-like gene was observed, suggesting that mir-143-37 could be intervening in the regulation of ubiquitination processes in salmon cells.

 Further studies  will  be necessary to validate these results . Nevertheless, our study suggests  that the pathogenicity process of P. salmonis could be regulated through s RNA. T his study highlights the potential use of s RNA as  a bacterial  attenuation technique.

Funding: ANID-Chile through and FONDAP (#15110027) and  Ph.D. Scholarship, No. 21191482