Gene and allele specific expression underlying the electric signal divergence in African weakly electric fish

Abstract

AbstractIn the African weakly electric fish genusCampylomormyrus, electric organ discharge (EOD) signals are strikingly different in shape and duration among closely related species, contribute to pre-zygotic isolation and may have triggered an adaptive radiation. We performed mRNA sequencing on electric organs (EOs) and skeletal muscles (SMs; from which the EOs derive) from three species with short (0.4 ms), medium (5 ms), and long (40 ms) EODs and two different cross-species hybrids. We identified 1,444 up-regulated genes in EO shared by all five species/hybrids cohorts, rendering them candidate genes for EO-specific properties inCampylomormyrus. We further identified several candidate genes, includingKCNJ2andKLF5, their up-regulation may contribute to increased EOD duration. Hybrids between a short (C. compressirostris) and a long (C. rhynchophorus) discharging species exhibit EODs of intermediate duration and showed imbalanced expression ofKCNJ2alleles, pointing towards a cis-regulatory difference at this locus, relative to EOD duration.KLF5is a transcription factor potentially balancing potassium channel gene expression, a crucial process for the formation of an EOD. Unraveling the genetic basis of the species-specific modulation of the EOD inCampylomormyrusis crucial for understanding the adaptive radiation of this emerging model taxon of ecological (perhaps even sympatric) speciation.