Autophagy-related genes in rainbow trout Oncorhynchus mykiss (Walbaum) gill epithelial cells and their role in nutrient restriction.

Autophagy is primarily an adaptive response to provide nutrients and energy following exposure to stress and starvation but can also regulate muscle mass and impact infectious disease susceptibility. Expression of 10 autophagy-related (Atg) genes in rainbow trout was monitored throughout the autophagosome formation cycle. The Atg gene sequences of rainbow trout were compared to other species to identify highly conserved regions and to generate primers. Phylogeny trees created with rainbow trout and 14 other species demonstrate that rainbow trout Atg gene sequences have greatest similarity to Atlantic salmon and other fish species. RTgill-W1 cells were subjected to nutrient restriction and compared to cells in normal nutrient conditions using quantitative reverse transcriptase polymerase chain reaction to assess changes in Atg gene expression. Nutrient restriction had a direct impact on Atg gene expression, with atg4, atg9, atg12, lc3, gabarap and becn1 undergoing the greatest differential expression (p < 0.05), most dramatically on Day 3. This was corroborated by Western blot detection of LC3, which also showed a peak of autophagy activity at Day 3 post-nutrient restriction. Atg gene expression revealed autophagy flux in RTgill-W1, as well as, those genes that were most significantly altered by nutrient restriction.