Extended Data Fig. 3: Chironomus does not form the CF at the head-trunk boundary; protein tree of predicted eve and btd orthologs in M. abdita and C. riparius.
From: Divergent evolutionary strategies pre-empt tissue collision in gastrulation
a, Phylogenetic distances of Even-skipped (Eve) and Buttonhead (Btd) orthologs in M. abdita (Mab), C. riparius (Cri), Tribolium castaneum (Tca), and related D. melanogaster proteins were calculated in Geneious using the Jukes-Cantor model. Only reliability values above 60% are shown. Eve trees use full-length alignment; Btd trees are based on alignment to residues 151–433. Scale bar indicates changes per site. RefSeq protein sequences from NCBI are Btd (Buttonhead, NP_511100), Cbt (Cabut, NP_722636), Eve (Even-skipped, NP_523670), Exex (Extra-extra, NP_648164), Pb (Proboscipedia, NP_476669), SP1 (SP1, NP_727360), and Spps (SP1 like factor, NP_651232), Tca-Btd (NP_001107792) and Tca-Eve (NP_001034538). b,c, Time-lapse images from single z-slices of live D. melanogaster (b, n = 6) and C. riparius (c, n = 5) embryos expressing membrane markers; regions span ~10–75% EL (D. melanogaster) and ~15–85% EL (C. riparius). T0 marks gastrulation onset. Colored lines highlight head-trunk boundaries - defined by the CF in D. melanogaster and by cell shape in C. riparius. Cyan dots track cells moving toward the boundary. Straightening occurs in both species, but C. riparius lacks the downstream cell shape changes and tissue flows seen during CF formation in D. melanogaster. Boxes indicate areas in d,e. Scale bars, 20 µm (b), 10 µm (c). d,e, Mesoscopic views at the head-trunk boundary in D. melanogaster (d) and C. riparius (e) at –3 and 0 min relative to gastrulation onset. Asterisks mark the CF region; arrows indicate apical area reduction in D. melanogaster, which is not seen in C. riparius. LUT bar shows cell area. Scale bars, 10 µm. Lower panels are also shown in Fig. 1m,n.
