In vivo localization of NvPar-3::mVenus during different stages of N. vectensis development. The overexpression of NvPar3::mVenus (A) protein, by mRNA microinjection, displays two phases of distribution, similar to what was observed in NvaPKC and NvPar-6: no asymmetric localization during earlier cleavage stages but differential localization along the A/B axis of the cells during later stages (blastula and gastrula). Interestingly, NvPar3::mVenus localizes only in the apico-lateral zone of the cells, presumably at the cell-cell junctions complex and centrosomes (arrowhead), and no signal was observed in the endoderm. NvPar3::mVenus was co-injected with Lifeact::mTq2 mRNA (B) to visualize the shape of the cells and the apical cortex. As is seen in (C), NvPar3::mVenus is below the cortical actin during all observed stages. White arrows indicate astral/centrosomal and (pro)nuclear structures. Images of unfertilized, cleavage, and side panels in gastrula stages correspond to a single slice from z-stack series. Image of the whole blastula and gastrula corresponds to a 3D reconstruction from z-stack series. Side panels in blastula and gastrula stages are a mid section from the z-stack series to show the apico-lateral distribution of NvPar3::mVenus along the A/B axis. See Additional files 21, 22, 23, 24, and 25 for more details of every stage presented here in C.