Differential gene expression in Hermissenda opalescens cerata tissue

Phagocytosis is a universal physiological process across eukaryotes with many important biological functions. In nudibranch gastropods, a novel form of phagocytosis called nematocyst sequestration is specialized for the uptake of venomous stinging organelles stolen from their cnidarian prey. This process is highly selective. Here we sequence mRNA from Hermissenda opalescens to identify genes enriched within the body regions where nematocyst sequestration occurs, and investigate how the expression profile of phagocytosis, immune, and digestive genes differs between nematocyst sequestering regions relative to those where other phagocytic functions occur. To do this experiment, animals were wild caught, then cerata were removed and allowed to regrow for 40 days. During this period, animals were fed nematocyst-containing or control food sources. Cerata were then removed after 40 days and sectioned into three parts: distal ceras (containing the cnidosac), proximal ceras (from the base of the ceras to 1/3 its length), and middle ceras (the remaining middle section of the tissue). RNA was extracted and selectively enriched for mRNA using polyA-selection. We identify 238 transcripts upregulated in the cnidosac of Hermissenda opalescens and describe general gene expression patterns.