The present study focuses on rather qualitative aspects of stripe formation and knockout responses to capture a unifying view among diverse striped patterns.
We consider L-iridophores that are located under the melanophore stripes to be dispensable for stripe formation, as they appear late in juvenile development after the basic striped pattern has been established.
These results suggest that parallel connection of FFL and negative FBL organizes the combinatorial stripe formation.
In the intermediate germ mode, genes regulated by a negative FBL (marked by Δ in Fig. 2C) show the sequential stripe formation, whereas genes regulated by FFLs (marked by+in Fig. 2C) show simultaneous stripe formation (Figs. S3C and S9C).
We identified necessary network module for each mode (Fig. 2D) and confirmed its function for the stripe formation (Fig. 3A C and Result S1).
The idea of controlling a Turing pattern with an imposed gradient was suggested 20 years ago for stripe formation during Drosophila development [28].
Genes located either within or directly downstream of a negative FBL are subjected to temporal regulation by the FBL (Fig. S9B), resulting in sequential stripe formation (Fig. S3B).
Second, the core networks were classified into long, short, and intermediate germ modes according to the exhibited mode of stripe formation as described above (see Methods).
Within approximately 1000 independent evolutionary trials, we discovered that the selected networks exhibit three basic modes of spatio-temporal gene expression (Figs. 1D F and S12): simultaneous, sequential, and combinatorial stripe formation.
Conservation of regulatory genes such as gap and pair-rule genes among arthropods indicates that the differences in the stripe formation have originated from architecture of the regulatory network.
In addition to simultaneous stripe formation of gene #1, expression of the upstream genes in the network (Fig. 2A) also follows a characteristic pattern observed in long germ insects [9], [24], [25] (Figs.
