Establishment of transgenic method in Trichoplax adhaerens

Trichoplax adhaerens is one of the simplest multicellular organisms belonging to the phylum Placozoa. Due to its basal position in the phylogenetic tree, Placozoa has become an important model for studying the origins of multicellular life. However, the lack of genetic manipulation techniques has limited most research to genomics, morphology, and behavioral studies. Developing genetic tools, such as transgenesis and gene editing, would greatly enhance research on this organism. Given the absence of sexual reproduction, traditional methods like single-cell microinjection are not feasible. Here, we establish a transgenic method for expressing exogenous genes in T. adhaerens. By evaluating different transfection strategies, we demonstrate that electroporation is an effective approach for ectopic gene expression in this species. We further optimized the electroporation conditions and successfully expressed GFP using various promoters. Additionally, we show that ectopic expression of the puromycin acetyltransferase (PAC) gene increases animals’ resistance to puromycin, suggesting a potential strategy for generating stable transgenic lines in the future. Our findings establish a method for gene expression in T. adhaerens, providing a valuable tool for molecular studies of this basal metazoan.