Bioactivity of recombinant human VEGF expressed by C. reinhardtii in vivo. Microalgae (red; chlorophyll auto fluorescence) were injected at 24 hpf into the yolk sack of transgenic zebrafish embryos expressing EGFP in endothelial cells. Three days after injection, vessels grew towards the injected algae expressing VEGF. This alteration in the vessel morphology was not observed in fish injected with wild-type algae or control injections. Z-projections of the fish and the yolk area are shown. Scale bar 150 μm. N ≥ 30. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)