Differential activity of transcription factors and neuronal effectors during the development of pikeperch brain.

Juvenile pikeperch (Sander lucioperca) undergo several ontogenetic shifts, the timing of which determines the survival of their first winter. The shift from planktivory to a more active piscivorous phenotype involves moving from pelagic to demersal habitat with more stimuli and hence potential brain functional reorganizations. During two consecutive years, we collected planktivores and piscivores with different body sizes between the years, recording distinct stages relative to the shift, and analyzed their whole-brain transcriptomes in an ecological context. We identified a distinct non-overlapping group of transcription factors (TFs) significantly upregulated in each phenotype: TFs upregulated in planktivores correspond to initial establishment of brain regions and overall architecture; TFs upregulated in piscivores correspond to the refinement of neurons and the formation of specific neuronal circuits. The planktivores independently of body size were characterized by interconnected activity of two TFs, fosab and junba. Gene set enrichment revealed extracellular matrix and collagen-related transcripts in piscivores from both years. A high activity of solute carrier (Slc) transporters was identified in the smaller-bodied piscivores. The neurotranscriptomics results reflected differences in body size and matched with ecological data and survival rates. The brain regulome indicated that body size differences translate into the specific gene activity of juvenile pikeperch.