Multiple tissue transcriptomic responses toPiscirickettsia salmonisin Atlantic salmon (Salmo salar)

Abstract

The bacterium Piscirickettsia salmonis is the etiological agent of salmonid rickettsial septicemia (SRS), a severe disease that causes major economic losses to the Atlantic salmon aquaculture industry every year. Little is known about the infective strategy of P. salmonis, which is able to infect, survive within, and replicate inside salmonid macrophages as an intracellular parasite. Similarly there is little knowledge concerning the fish host's response to invasion by this pathogen. We have examined the transcriptional response of postsmolt Atlantic salmon (Salmo salar) to P. salmonis at 48 h following infection in three tissues, liver, head kidney, and muscle, using an Atlantic salmon oligonucleotide microarray (Salar_2, Agilent 4x44K). The infection led to a large alteration of transcriptional activity in all the tissues studied. In infected salmon 886, 207, and 153 transcripts were differentially expressed in liver, head kidney, and muscle, respectively. Assessment of enrichment for particular biological pathways by gene ontology analysis showed an upregulation of genes involved in oxidative and inflammatory responses in infected fish, indicative of the activation of the innate immune response. The downregulation of genes involved in the adaptive immune response, G protein signaling pathway, and apoptotic process in infected fish may be reflective of mechanisms used by P. salmonis to survive, replicate, and escape host defenses. There was also evidence of differential responses between studied tissues, with protein metabolism being decreased in muscle of infected fish and with a concomitant increase being shown in liver

Patterns of Piscirickettsia salmonis load in susceptible and resistant families of Salmo salar

“…On the other hand, the susceptible fish was not able to mount an efficient immune response, due to an exacerbated, yet inefficient, immunological response. Similar findings have been reported previously [8,9]. This could be one of the possible factors involved in the relative low rate of success when using antimicrobial drug treatments for controlling P. salmonis [16].…”

“…McCarthy et al [7] detected the bacteria in cytoplasmic vacuole of macrophages in head kidney and spleen obtained from Salmon Rickettsial Syndrome (SRS) affected fishes. Therefore, the head kidney has been considered a key organ for studying the host response to this pathogen, and this has been validated at the transcriptomic level [8,9]. However, little is known about several aspects of host-pathogen interaction, such as for example, the bacterial load in resistant versus susceptible fish.…”

Influence of dietary inclusion of a wet processed faba bean protein isolate on post-smolt Atlantic salmon ( Salmo salar )

“…However, the transcriptomic response in pyloric caeca gave no obvious clues the chemical identity of the factor provoking the adverse reaction, which was perhaps not surprising. There are few studies investigating the molecular response of pyloric intestine to reinforce the present data (Morais et al, 2012;Betancor et al, 2015;De Santis et al, 2015c) as most studies on the effects of dietary plant proteins have focussed on distal intestine (Tacchi et al, 2011(Tacchi et al, , 2012Kortner et al, 2012;Sahlmann et al, 2013;De Santis et al, 2015d;Krol et al, 2016). In salmon fed increasing levels of soybean meal that provoked increasing enteritis, digestive enzyme activities in distal intestine were decreased, as observed in the present study (Krogdahl et al, 2003).…”

“…A-MEXP-2065) described in detail previously (Tacchi et al 2011). Briefly, RNA was extracted from 50 mg of liver tissue or pyloric caeca using TRI Reagent (Sigma-Aldrich, Additionally, features consistently expressed just above background noise (defined as those features whose intensity was lower than 5th percentile of the distribution in 75% or more of the analysed samples) were also removed.…”

Functional Divergence of Type 2 Deiodinase Paralogs in the Atlantic Salmon

“…As before, SW exposure for 6 hr induced dio2a expression, while having no detectable influence on dio2b ( Figure S4). Using a previously validated customized salmon microarray [23], we identified 1,939 genes whose expression was significantly (p < 0.05) increased or decreased by transfer from FW to SW for 6 hr. For a subset of 259 genes, this SW response was abolished if IOP was added to the SW, but maintained if T3 was also present during IOP treatment.…”