Highly efficient transgenesis with miniMos in Caenorhabditis briggsae

Abstract

C. briggsae as a companion species for C. elegans has played an increasingly important role in study of evolution of development, gene regulation and genome. Aided by the isolation of its sister spices, it has recently been established as a model for speciation study. To take full advantage of the species for comparative study, an effective transgenesis method especially those with single copy insertion is important for functional comparison. Here we modified a transposon-based transgenesis methodology that had been originally developed in C. elegans but worked marginally in C. briggsae. By incorporation of a heat shock step, the transgenesis efficiency in C. briggsae with single copy insertion is comparable to that in C. elegans. We used the method to generate 54 independent insertions mostly consisting of a mCherry tag over the C. briggsae genome. We demonstrated the use of the tags in identifying interacting loci responsible for hybrid male sterility between C. briggsae and C. nigoni when combined with the GFP tags we generated previously. Finally, we demonstrated that C. briggsae has developed native immunity against the C. elegans toxin, PEEL-1, but not SUP-35, making the latter a potential negative selection marker against extrachromosomal array.\n\nSummaryNematode C. briggsae has been used for comparative study against C. elegans over decades. Importantly, a sister species has recently been identified, with which C. briggsae is able to mate and produce viable hybrid progeny. This opens the possibility of using nematode species as a model for speciation study for the first time. To take full advantage of C. briggsae for comparative study, an effective transgenesis method to generate single copy insertion is important especially for functional comparison. An attempt was made previously to generate single copy insertion with transposon-based transgenesis methodology, which had been originally developed in C. elegans but with limited success in C. briggsae. Here we modified the transposon-based methodology by incorporation of a heat shock step, which allows us to achieve a much higher transgenesis efficiency in C. briggsae with single copy insertion. We used the method to generate 54 independent insertions mostly consisting of a mCherry tag over the C. briggsae genome. We demonstrated the use of the tags in identifying interacting loci responsible for hybrid male sterility between C. briggsae and C. nigoni when combined with the GFP tags we generated previously. Finally, we demonstrated that C. briggsae has developed native immunity against the C. elegans toxin, PEEL-1, but not SUP-35, making the latter a potential negative selection marker against extrachromosomal array. Taken together, the modified transgenesis methodology and the transgenic strains generated in this study are expected to further facilitate C. briggsae as a model for comparative study or speciation study.