Differential gene expression in small and large rainbow trout derived from two seasonal spawning groups

Area of Science:

• Aquaculture and Fish Biology
• Molecular Biology and Genomics
• Comparative Physiology

Background:

• Fish growth is influenced by genetics, environment, and physiology.
• Previous studies focused on specific growth conditions like refeeding or hormonal manipulation.
• This study investigates gene expression in large vs. small, genetically similar rainbow trout under standard conditions.

Purpose of the Study:

• To determine gene expression profiles in rainbow trout (Oncorhynchus mykiss) white muscle and liver.
• To assess the influence of season (September vs. December) and body size (large vs. small) on gene expression.
• To identify potential biomarkers for growth in rainbow trout.

Main Methods:

• Gene expression profiling using microarrays in white muscle and liver tissues.
• Comparison of gene expression between large and small fish from two seasonal groups (September and December lots).
• Analysis of gene ontology categories related to growth, stress, and localization.

Main Results:

• Few differences in liver gene expression, but white muscle showed significant variations between seasonal groups and sizes.
• Large fish exhibited up-regulation of cytoskeletal genes; small fish showed myofibril component gene up-regulation.
• Genes related to immunity were up-regulated in large fish, while apoptosis-related genes were up-regulated in small fish, particularly in the 'response to stress' category.

Conclusions:

• White muscle gene expression patterns are consistent within size classes across seasons, suggesting utility as growth biomarkers.
• Smaller fish in September exhibited greater sensitivity to stress and external stimuli compared to larger fish.
• Seasonal sampling significantly impacted gene expression related to growth processes in rainbow trout.