Transcriptome Analysis of Turbot (Scophthalmus maximus) Infected With Aeromonas salmonicida Reveals a Direct Effect on Leptin Synthesis as a Neuroendocrine Mediator of Inflammation and Metabolism Regulation

Abstract

Aeromonas salmonicida subsp. salmonicida is the causative agent of furunculosis, a disease affecting numerous fish species worldwide. It is a highly pathogenic bacterium for turbot, whose farming production represents an important economic activity in several European countries and China. To better understand the response of this organism to A. salmonicida, we conducted RNA-Seq analysis of the head kidney from experimentally infected and uninfected turbot juveniles at 24 hours post-infection (hpi). As expected, among the differentially expressed genes (DEGs) between infected and uninfected fish, we observed the modulation of a multitude of immune-related genes but also a high representation of genes linked to metabolism. Interestingly, one of the most upregulated genes was that encoding the hormone leptin. Leptin is a multifunctional hormone/cytokine that has been shown to play roles in the immune system, stress response, food intake, metabolism and energy balance. We used recombinant human leptin to elucidate its role during infection with A. salmonicida in turbot (anorexigenic activity, ability to modulate metabolism and the immune response, and its effect on survival and bacterial load during infection). We found that the intraperitoneal administration of leptin was able to alter the response to the bacteria at the immune level, but especially at the metabolic level, which resulted in a higher survival rate without affecting the bacterial load. Based on this, we hypothesized that leptin could offer great potential as a therapeutic treatment during furunculosis outbreaks by reducing the impact of sepsis. Our results reveal the complex interplay between bacterial activity and the regulation of food intake, metabolism and inflammation.

Integration of host-pathogen functional genomics data into the chromosome-level genome assembly of turbot (Scophthalmus maximus)

“…In this study, an integrated up-to-date genomic atlas of functional transcriptomic features related to resistance for major turbot aquaculture diseases was accomplished. Previously reported differentially expressed genes (DEG) derived from microarray in response to Aeromonas salmonicida (AS; Millán et al, 2011), Philasterides dicentrarchi (PD; Pardo et al, 2012) and the Viral Haemorrhagic Septicaemia virus (VHSV; Díaz-Rosales et al, 2012), and RNAseq data in response to Enteromyxum scophthalmi (ES; Robledo et al, 2014;Ronza et al, 2016) and AS (Librán-Pérez et al, 2022) were reannotated and mapped to the updated and contiguous genome assembly of the species (Martínez et al, Fig. 3.…”

“…Data for other QTL and trait associated markers such as sex determination, impact of domestication and balancing/divergent selection were published by Martínez et al (2009) and do Prado et al (2018a, 2018b. Sets of accessible DNA sequences for differentially expressed genes (DEG) in response to infections by AS, PD, VHSV and Enteromyxum scophthalmi (ES) were published by Millán et al (2011), Pardo et al (2012), Díaz-Rosales et al (2012, Robledo et al (2014), Ronza et al (2016) and Librán-Pérez et al (2022). Finally, a study on Runs of Homozygosity islands (ROHi) and signatures of selective sweeps was carried out by Aramburu et al (2020).…”

“…Another 127 oligo-probes (Millán et al, 2010), corresponding to 65 DEG in head kidney from VHSV intraperitoneally infected turbot (Díaz-Rosales et al, 2012), were also included. On the other hand, we also considered DNA sequences for 4295, 1173 and 2056 DEG derived from RNAseq data detected in head kidney, liver, and pyloric caeca in response to severe (Robledo et al, 2014) and early (Ronza et al, 2016) ES infection stages, and head kidney in response to AS infection (Librán-Pérez et al, 2022), respectively.…”

“…In bold, newly annotated genes; underlined nearby genes to the oligos of DEG in the microarray analysis. Original studies: AS (Millán et al, 2011;Librán-Pérez et al, 2022); PD (Pardo et al, 2012); VHSV (Díaz-Rosales et al, 2012), ES (Ronza et al, 2016;Robledo et al, 2014). Gene descriptions: ctrl1-like (chymotrypsin-like protease CTRL-1), rtp3-like (receptor-transporting protein 3-like), comtd1 (catechol O-methyltransferase domain-containing protein 1), muc2-like (mucin-2-like), agxtb (alanine-glyoxylate and serine-pyruvate aminotransferase b), il8-like (interleukin-8-like), pyroxd2 (pyridine nucleotide-disulfide oxidoreductase domain-containing protein 2), hpxb (hemopexin), S100P-like (protein S100-P-like), fabp10a (fatty acidbinding protein 10-A), apoc2 (apolipoprotein C-II), apoc4 (apolipoprotein C-IV), apoa1-like (apolipoprotein A-I-like), try2-like (trypsin-2-like), try1 (trypsin-1), itih2 (inter-alpha-trypsin inhibitor heavy chain H2), slc7a1-like (high affinity cationic amino acid transporter 1-like), vtnb (vitronectin b), mmp13-like (collagenase 3-like), ctrb-like (chymotrypsin B-like), hp (haptoglobin), sall1a (sal-like protein 1a), itih3-like (inter-alpha-trypsin inhibitor heavy chain H3-like), endou (poly(U)-specific endoribonuclease-A), aldh1I1 (cytosolic 10-formyltetrahydrofolate dehydrogenase), higd1a (HIG1 domain family member 1A), tfa (transferrin-a), ahsg2 (alpha-2-HS-glycoprotein 2), srd5a1 (3-oxo-5-alpha-steroid 4dehydrogenase 1), msmb-like (beta-microseminoprotein-like), fabp (fatty acidbinding protein, liver-type-like), gstt1a (glutathione S-transferase theta-1a), cpa1-like (carboxypeptidase A1-like), myo9Ab-like (unconventional myosin-IXAb-like), serpinc1 (antithrombin-III), fetub (fetuin-B), cp (ceruloplasmin), agxta (alanine-glyoxylate and serine-pyruvate aminotransferase a), dusp1 (dual specificity protein phosphatase 1), slc40a1 (solute carrier family 40 member 1), etv5a (ETS translocation variant 5a), habp2-like (hyaluronan-binding protein 2like), mpx (eosinophil peroxidase), fbp1-like (fructose-1,6-bisphosphatase 1like), vmo1-like (vitelline membrane outer layer protein 1-like), serpina10 (protein Z-dependent protease inhibitor), adh1 (alcohol dehydrogenase 1), kcnh4b (potassium voltage-gated channel subfamily H member 4), ddit4 (DNA damage-inducible transcript 4 protein), co1a1b (collagen type I alpha 1b), prmt1 (protein arginine N-methyltransferase 1), ighe (immunoglobulin epsilon heavy chain), dhx58 (probable ATP-dependent RNA helicase DHX58), leg1.1 (liver-enriched gene 1, tandem duplicate 1.…”

“…In the case of turbot, a custom oligo-microarray enriched for immune genes was designed (Millán et al, 2010) and used for identifying DEG and enriched functions regarding response against AS (Millán et al, 2011), PD (Pardo et al, 2012;Valle et al, 2020) and VHSV (Díaz-Rosales et al, 2012;Pereiro et al, 2014). Later RNA-seq, a more sensitive and accurate technique that can distinguish expression profiles of paralogous genes and identify gene-associated single nucleotide polymorphisms (Ronza et al, 2019), was applied on infections with the intestinal parasite E. scophthalmi during late (Robledo et al, 2014) and early (Ronza et al, 2016) enteromyxosis stages, as well as to revisit the study of infections with PD (Valle et al, 2020) and AS (Librán-Pérez et al, 2022) with this new technology.…”