Movie 1.

epi:eGFP-positive cells at the venous pole switch off GFP expression and start expressing myl7:mRFP when entering the heart tube. In vivo time-lapse imaging of a epi:GFP;myl7:mRFP heart between 52 hpf and 68 hpf. The yellow arrow highlights a cell that initially is only GFP positive and latter stops expressing GFP and starts to express RFP. The cyan arrows point to cardiomyocytes in the heart tube that are still GFP-positive at the beginning of the Movie and then loose GFP signal concomitant with increase in mRFP signal intensity. Images were acquired with the Leica TCS SP8 DLS. Shown is a single plane reconstruction of the beating. Scale bar, 50 μm.