Figure 7.

Schematic diagram reveals predicted molecular mechanism regulating the response to the loss-of-function mutation of SLC45A2 in C. argus. The mutation of SLC45A2 induces melanosomal acidification, leading to the inactivation of TYR and therefore the failure to synthesize melanin in YM snakehead. Due to the lack of melanin, UV irradiation penetrating through the epidermis increases dramatically and triggers the dermal fibroblast-derived melanogenic factors (TGF-β, FGF, SFRP and Sema7a), which act on the melanophore by binding to receptors and modulating intracellular signalling cascades (MAPK, WNT and calcium). The induced signalling pathways elevate the phosphorylation of MITF, thereafter upregulating the downstream key melanogenesis genes (tyr, tyrp1, dct and pmel). Red font indicates the significantly upregulated DEGs. The full names of these genes are listed in the electronic supplementary material, table S6.