Comparative transcriptome analysis reveals ectopic delta-5 and delta-6 desaturases enhance protective gene expression upon Vibrio vulnificus challenge in Tilapia (Oreochromis niloticus)

Abstract

Background Tilapia (Oreochromis niloticus) cultures are frequently infected by Vibrio vulnificus, causing major economic losses to production units. Previously, tilapia expressing recombinant delta-5 desaturase and delta-6 desaturase (D56) were found to be resistant to V. vulnificus infection. In this report, we profile the D56-mediated molecular changes underlying this resistance in tilapia. A comparative transcriptome analysis was performed on V. vulnificus-infected wild-type and D56-transgenic tilapia using Illumina’s sequencing-by-synthesis approach. Gene enrichment analysis on differentially expressed unigenes was performed, and the expression patterns were validated by real-time PCR. Results Comparative transcriptome analysis was performed on RNA-sequence profiles obtained from wild-type and D56-transgenic tilapia at 0, 6 and 24 h post-infection with V. vulnificaus. GO and KEGG gene enrichment analyses showed that D56 regulates several pathways and genes, including fatty acid (FA) metabolism associated, and inflammatory and immune response. Expression of selected FA metabolism-associated, inflammatory and immune responsive genes was validated by qPCR. The inflammatory and immune responsive genes that are modulated by FA-associated D56 likely contribute to the enhanced resistance against V. vulnificus infection in Tilapia. Conclusions Transcriptome profiling and filtering for two-fold change variation showed that 3795 genes were upregulated and 1839 genes were downregulated in D56-transgenic tilapia. These genes were grouped into pathways, such as FA metabolism, FA elongation, FA biosynthesis, biosynthesis of unsaturated FA, FA degradation, inflammation, immune response, and chemokines. FA-associated genes and immune-related genes were modulated by D56 at 6 h and 24 h post infection with V. vulnificus. The expression patterns of FA-related genes, inflammatory genes, antimicrobial peptide genes and immune responsive genes at 0, 3, 6, 12, 24 and 48 h post-infection suggests these genes are involved in the enhanced resistance of D56 transgenic tilapia to V. vulnificus.

Genomics‐driven prophylactic measures to increase streptococcosis resistance in tilapia

“…To date, numerous genomic tools have been developed for this species (Yáñez et al, 2020). These genomic tools have been used in studies to decipher sex determination (Cnaani et al, 2004;Kocher et al, 1998;Lee et al, 2005), to assess genetic variability and reconstruct pedigrees (Guyon et al, 2012;Joshi et al, 2018), to quantitative trait loci (QTLs), expressed sequence tags (ESTs), genome-wide association studies (GWAS), and marker-assisted selection (Lee et al, 2010;Liu et al, 2013Liu et al, , 2014Yoshida et al, 2019;Yu et al, 2021); and to assess genomic selection and gene function (Chu et al, 2021;Joshi et al, 2021;Tu et al, 2021). The genomic tools used in the selective breeding of tilapia are described in the literature and their highlight discoveries are listed in Table 1.…”