Fig. 6: Out-of-plane division acts as an alternative mechanical sink to mitigate tissue collision.
From: Divergent evolutionary strategies pre-empt tissue collision in gastrulation
a,b, Lateral surface projection of the D. melanogaster head region showing MD1 and MD5 (a, yellow dashed outlines), and cellular view of telophase cells in MD5 (b) in control or InscOE embryo, visualized with membrane (3xmScarlet-CaaX, green) and MyoII (Sqh–eGFP, magenta) markers (n = 5). Yellow arrows, CF; white arrows, cytokinetic rings. c,d, Apical surface area of MD1 (c) and MD5 (d) in control or InscOE embryos injected with btd RNAi (n = 5 and 6, respectively) as a function of time, normalized to surface area at gastrulation onset. Bold lines indicate means and the shaded region indicates standard errors. Two-sided t-test on maxima. *P = 0.0166, ****P < 0.0001. e, Lateral surface projection (top) and z-axis reslice (bottom) of embryos with btd RNAi (n = 8) and btd RNAi with InscOE (xlass I, n = 7; class II, n = 6). Membranes visualized with 3xmScarlet-CaaX. Magenta arrows and dashed outlines indicate head–trunk buckling and the blue dashed outline indicates buckling between MD1 and MD5. f,g, Maximum depths (f) or durations (g) of head–trunk buckling in btd RNAi embryos with and without InscOE. Each dot represents an embryo, bold lines indicate the median and whiskers mark the 95% confidence interval. One-way ANOVA Tukey post hoc test. ****P < 0.0001 (P = 0.000000001), **P < 0.01 (P = 0.0013) (f) and ****P < 0.0001 (P = 0.00003); NS, not significant, P > 0.05 (P = 0.782) (g). h, Schematic representation of our model illustrating the divergent strategies preventing head–trunk tissue collision in cyclorrhaphan and non-cyclorrhaphan flies, based on our findings in D. melanogaster (top) and C. riparius (bottom). See Supplementary Note 6 for more details. Scale bars, 50 µm (a), 5 µm (b) and 30 µm (e).
