Salmonid microarrays identify intestinal genes that reliably monitor P deficiency in rainbow trout aquaculture

• Published in: Animal genetics 2007-08, Vol.38 (4), p.319-331
• Main Authors: Kirchner, S, McDaniel, N.K, Sugiura, S.H, Soteropoulos, P, Tian, B, Fletcher, J.W, Ferraris, R.P
• Format: Article
• Language: English
• Subjects: Animal Feed; Animals; Aquaculture; dietary deficiency; Fish Proteins - genetics; Fish Proteins - physiology; Gene Expression Profiling; Gene Expression Regulation; Genetic Markers; immune response; intestine; Intestine, Small - metabolism; Oligonucleotide Array Sequence Analysis; Oncorhynchus mykiss; Oncorhynchus mykiss - genetics; Oncorhynchus mykiss - metabolism; Phosphorus - blood; phosphorus-responsive genes; RNA, Messenger - metabolism; Salmo salar; trout
• ISSN: 0268-9146; 1365-2052
• DOI: 10.1111/j.1365-2052.2007.01615.x

Nutrient-responsive genes can identify important metabolic pathways and evaluate optimal dietary levels. Using a 16K Salmo salar microarray, we identified in rainbow trout (Oncorhynchus mykiss) 21 potential phosphorus (P)-responsive genes, mainly involved in immune response, proteolysis or transport, whose expression levels changed in the intestine after 5 days of feeding a low-P (LP) diet. Diet-induced changes in the expression levels of several genes in each fish were tightly correlated with changes in serum P, and the changes persisted for an additional 15 days after dietary P deficiency. We then evaluated these and previously identified P-responsive genes under simulated farm conditions, and monitored the intestinal gene expression from 6 h to 7 days after the trout were switched from a sufficient-P (SP) diet to a LP diet (SP[rightward arrow]LP), and from a LP diet to a SP diet (LP[rightward arrow]SP). After 7 days, mean serum P decreased 0.14 m M/day for SP[rightward arrow]LP and increased 0.10 m m/day for LP[rightward arrow]SP. The mRNA abundance of the metalloendopeptidase meprin 1α (MEP1α), the Na⁺-dependent phosphate co-transporter (NaPi2b,SLC34A2), the sulfotransferase SULT2β1 and carbonic anhydrase XIII genes all increased after SP[rightward arrow]LP and decreased after LP[rightward arrow]SP, suggesting that adaptive expression is reversible and correlated with dietary P. The duration of change in gene expression in response to SP[rightward arrow]LP was generally shorter than that of LP[rightward arrow]SP, suggesting potentially different mechanisms of adaptation to deficiency as opposed to excess. Diet-induced changes in mRNA abundance of other genes were either transient or modest. We identified, by heterologous microarray hybridization, new genes sensitive to perturbations in dietary P, and then showed that these genes can reliably monitor P deficiency under field conditions. Simultaneous changes in the expression of these P biomarkers could predict either P deficiency (to prevent economic losses to the farmers) or P excess (to prevent inadvertent pollution of nearby waters).