Exploring Development in Slow- and Fast-Growing Seriola dorsalis Larvae Using RNA-Seq

The California yellowtail (Seriola dorsalis) is a strong candidate for development of offshore commercial aquaculture in southern California and neighboring Baja California. Production from broodstock populations has been successful but has not yet reached a level where it can satisfy largescale production demand, due in part to difficulties from highly variable survival and growth rates through the larval stages. Extremely fast growth and major physical changes characterize the earliest life stages; one way to examine survival and growth variability is at the gene and molecular levels across those early-developmental periods. To improve our understanding of the molecular processes underlying development, we examined RNA-Seq profiles for several early life stages of yellowtail, categorized as either slow- or fast-growing. Gene expression was measured in three replicates of pooled larval samples at 2, 7, and 17 days post hatch for these two growth categories. Using the Illumina platform, an average of sixty million reads was obtained per replicate; genes of related function were sorted into clusters, and those found at high frequency in the differential gene expression set were identified. Differences in molecular pathways, biological processes, and gene regulating patterns between the two fitness groups were examined. There were many differentially expressed genes across developmental stages and between the fitness groups, for example, genes involved in oxidative phosphorylation pathways revealed interesting patterns both across developmental stages and between slow- and fast-growing larvae. Results of these analyses will be presented.