Fig. 1
From: Non-canonical dorsoventral patterning in the moth midge Clogmia albipunctata
Schematic representation of the shuttling mechanism underlying DV patterning in Drosophila melanogaster (a–d) and phylogeny of species mentioned in the text (e). Circles in a–d represent transverse sections through blastoderm embryos. a mRNA expression patterns for the main components of the shuttling mechanism: green: scw; light blue: sog; blue: dpp; maroon: tsg; purple: tld. b Initial localisation of protein products. DPP and SCW form homo- and heterodimers. SOG diffuses towards the dorsal midline forming a concentration gradient (light blue triangle). Magenta: TKV. c Initial stages of the shuttling mechanism. BMP ligand dimers enter into the heteromeric DPP-SOG-SCW-TSG shuttling complex, which diffuses dorsally driven by the SOG gradient. The TLD protease cleaves SOG at the dorsal midline, releasing TSG and BMP dimers from the complex. SOGc refers to cleaved SOG. d Released BMP ligand dimers bind their receptors, activating an intracellular signalling cascade mediated by MAD phosphorylation (pMAD) at the dorsal midline. pMAD translocates to the nucleus and induces target genes in a concentration-dependent manner, thereby inducing dorsal fate. e Phylogenetic tree showing the main groups of insects, and the species discussed in this paper. In black lines, holometabolous insects. Phylogeny based on Misof et al. [81]. See text for further details