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- Francisella noatunensis modulates the hepatic profile of fatty acids in Patagonian blennie Eleginops maclovinusPublication . Oyarzún-Salazar, R.; Lagos, Carolina; Orellana, P.; Dantagnan, P.; Muñoz, J.L.P.; Romero, A.; Vargas-Chacoff, L.Fatty acids (FA) have been reported to play a role in the defense against bacterial pathogens. However, studies in fish are limited and no information exists on the modulation of FA of Eleginops maclovinus challenged with the pathogen of aquaculture relevance Francisella noatunensis. We inoculated 144 fish intraperitoneally with 3 doses (low dose [LD]: 1 x 101 bact/mu L; medium dose [MD]: 1 x 105 bact/mu L; high dose [HD]: 1 x 1010 bact/mu L) and a control dose (sterile culture medium, [C]) of the bacteria F. noatunensis and took liver samples at 1, 3, 7, 14, 21, 28 days post-inoculation (dpi). The LD of F. noatunensis did not present significant differences to the C, except for the C20:4n6 (ARA) at day 28, while the MD and HD of F. noatunensis did generate a significant effect of the FA profile of E. maclovinus. We observed a greater modulation after administering the HD of bacteria and detected significant differences from day 3 post-inoculation (P < 0.05). Significantly high levels of C18:0 was detected at day 28 (P < 0.05), while significantly low levels of C14:0, C20:0, C16:1, C18:1n9, C18:2n6; C18:3n3, and C20:5n3 were detected at different dpi of F. noatunensis (P < 0.05). ARA and C22:6n3 (DHA) showed a significant decrease during the first dpi (P < 0.05) but later they showed an increase in their levels, with ARA increasing its levels from day 14 (P < 0.05), while DHA increased its levels only at day 28 (P < 0.05). A large number of FA were highly correlated with each other and multivariate statistical analyzes (PCA and random forest) were able to detect the HD of F. noatunensis as the dose that most affects the FA profile of E. maclovinus, while the LD, MD and C cannot be differentiated in their FA profile. The FA most affected by the challenge with F. noatunensis were C18:2n3 and C18:3n3 (P < 0.05). Our results suggest a relationship between the bioavailability of FA in the liver and the level of the physiological response of E. maclovinus to an experimental challenge with F. noatunensis and suggest that hepatic FA modulation may explain or be part of the high tolerance to bacterial infections reported for E. maclovinus, although more studies are necessary to clarify the roles of the different types of FA on pathogen-host dynamics and its potential use in combating fish pathogenic bacteria.
- Transcriptomic analysis of differentially expressed genes in kidney and intestine of dicentrarchus iabrax fed different nutritional amounts of inorganic phosphatePublication . Vargas Lagos, Carolina Fabiola; Silva, Sandra; Guerrero, Laura; Oca, Marco Montes de; Louro, Bruno; Carvalho Alves, Alexandra; Rotllant, Josep; Guerreiro, Pedro MiguelPhosphorus (P), in the form of inorganic phosphate (Pi), is one of the most important macronutrients for all organisms, including fish. It is indispensable for the formation of hard tissues such as bones, but also for cell signalling and cell membrane formation, and energy transduction, among many other functions and is kept under well-controlled conditions, since its deficiency or overload may lead to skeletal malformation or ectopic calcification, disturbances of intermediary metabolism, growth and function impairment, endocrine dysfunction, and eventually death. Fish feeds used in aquaculture are therefore P-rich but excess/unused/excreted P in the effluents can lead to eutrophication and a consequent deleterious change in the aquatic ecosystem. The objective of this study was to evaluate the expression profiles and transcripts modified by dietary P, to identify pathways and mechanisms involved in P transport and regulation in the kidney and intestine. Juvenile Dicentrarchus labrax were fed using a commercial feed (1.1% P) or tailored-made feeds containing 0.05%, 1.1%, or 3% Pi. Fish (duplicate tanks, n = 10) were fed for 70 days and weighed periodically to evaluate growth changes. Kidney and intestine were used for RNA extraction. Next-Generation Sequencing and RNAseq library preparation were performed in an Illumina system following the manufacturer’s recommendations. Annotation was performed using the available sea bass genome assembly. Bioinformatic analysis showed significant differences in expression patterns among the three conditions tested in both tissues. In the kidney, increased P led to a total of 135 differentially expressed genes (DEGs; 82 up and 53 down), while only 54 (11 up and 43 down) genes responded to P restriction. In the intestine, high P affected the expression of 50 genes (16 up and 34 down) whereas only 26 (6 up and 20 down) were modified by low P. However, DEGs between high and low P were 156 in kidney and 154 in intestine. Preliminary analysis suggests the most affected pathways were those involved in cellular metabolism and phosphorylation but also on the structure of cell membranes, either for maintaining membrane integrity or in genes related to transmembrane ion transport. We expect this research to reveal the molecular implications of dietary P imbalance looking at specific targets such as membrane transporters and regulatory factors, but also to the larger metabolic pathways affected in these two key organs for P uptake and excretion.