BACKGROUND: Fluorescent proteins such as the green fluorescent protein (GFP) 
have widely been used in transgenic animals as reporter genes. Their use in 
transgenic Xenopus tadpoles is especially of interest, because large numbers of 
living animals can easily be screened. To track more than one event in the same 
animal, fluorescent markers that clearly differ in their emission spectrum are 
needed.
RESULTS: We established the transgenic Xenopus laevis strain tom3 that expresses 
ubiquitously red fluorescence from the tdTomato gene through all larval stages 
and in the adult animal. This new tool was applied to track transplanted 
blastemas obtained after tail amputation. The blastema can regenerate ectopic 
tails marked by red fluorescence in the host animal. Surprisingly, we also found 
contribution of the host animal to form the regenerate.
CONCLUSION: We have established a useful new tool to label grafts in Xenopus 
transplantation experiments.