Fig. 2. Long-term time-lapse confocal imaging reveals cellular dynamics of meristem initiation and proliferation in the Ceratopteris gametophyte.

a–v One hermaphroditic gametophyte expressing the nuclear marker H2B-GFP (at 5 DAI) was live-imaged through laser scanning confocal microscopy. The non-invasive time-lapse imaging was performed at 6-h intervals, from 0 h to 126 h. a–v Z-projection views of confocal images at the indicated time points are shown. White arrows indicate formation and proliferation of the multicellular meristem over time. Three archegonia subsequently formed next to the meristem, which are highlighted with the circles in different colors (orange, blue and pink). w Merge of the GFP (v) and DIC (showing the cell outlines) channels. The white asterisk indicates ruptured spore coat, and the white arrowhead indicates rhizoids. Scale bars: 50 μm. Three independent biological replicates were included in this time-lapse imaging experiment with the same interval and duration, all showing similar patterns of prothallus cell proliferation. Two other samples were shown in Supplementary Figs. 4 and 5.