Abstract
BackgroundThe Midas cichlid species complex (Amphilophus spp.) is widely known among evolutionary biologists as a model system for sympatric speciation and adaptive phenotypic divergence within extremely short periods of time (a few hundred generations). The repeated parallel evolution of adaptive phenotypes in this radiation, combined with their near genetic identity, makes them an excellent model for studying phenotypic diversification. While many ecological and evolutionary studies have been performed on Midas cichlids, the molecular basis of specific phenotypes, particularly adaptations, and their underlying coding and cis-regulatory changes have not yet been studied thoroughly.ResultsFor the first time in any New World cichlid, we use Tol2 transposon-mediated transgenesis in the Midas cichlid (Amphilophus citrinellus). By adapting existing microinjection protocols, we established an effective protocol for transgenesis in Midas cichlids. Embryos were injected with a Tol2 plasmid construct that drives enhanced green fluorescent protein (eGFP) expression under the control of the ubiquitin promoter. The transgene was successfully integrated into the germline, driving strong ubiquitous expression of eGFP in the first transgenic Midas cichlid line. Additionally, we show transient expression of two further transgenic constructs, ubiquitin::tdTomato and mitfa::eGFP. Transgenesis in Midas cichlids will facilitate further investigation of the genetic basis of species-specific traits, many of which are adaptations.ConclusionTransgenesis is a versatile tool not only for studying regulatory elements such as promoters and enhancers, but also for testing gene function through overexpression of allelic gene variants. As such, it is an important first step in establishing the Midas cichlid as a powerful model for studying adaptive coding and non-coding changes in an ecological and evolutionary context.
Highlights
The Midas cichlid species complex (Amphilophus spp.) is widely known among evolutionary biologists as a model system for sympatric speciation and adaptive phenotypic divergence within extremely short periods of time
Biologists have long been fascinated by these teleosts and numerous studies have been conducted on aspects of cichlid biology such as their strikingly diverse color patterns [3, 4], morphologies [5, 6] and behaviors [7, 8]
To generate stable transgenic lines, recombinant DNA has to be integrated into the germline
Summary
The Midas cichlid species complex (Amphilophus spp.) is widely known among evolutionary biologists as a model system for sympatric speciation and adaptive phenotypic divergence within extremely short periods of time (a few hundred generations). Transgenesis technology has increasingly been applied to non-model organisms, especially driven by the use of the Tol transposon-mediated insertion technology that strongly increases the insertion efficiency of recombinant DNA [11]. This expands this powerful toolset to organisms of evolutionary and ecological interest including sticklebacks [12], African cichlids [13] and killifish [14]. We have successfully adapted and optimized Tol2-mediated transgenesis for the first time in a cichlid from the New World, the Midas cichlid species complex, Amphilophus spp
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