DmZPC5 transgenic zebrafish showed improved melting point depression compared with that observed in the chorions of the tropical fish.

(a) The construct used to establish the transgenic line. The letter ‘p’ represents the DrZP3 promoter. (b) Immunohistochemical staining showing the localization (the sheets of brown dots indicated by the arrows) of the DmZPC5 transgene product in the chorion of the two transgenic fishes (DrZP3::DmZPC5-a (pictures 3, 4), -b (pictures 5, 6)) and the lack of staining in wild-type (WT, pictures 1, 2) chorions. Scale bar for pictures 1, 3, 5 is 40 μm and scale bar for pictures 2, 4, 6 is 10 μm. The tissues shown were taken from adult fish ovary. (c) Enhanced MPD (left panel) and ice-faceting activity (right panel) were detected in the transgenic zebrafish chorions. The bars represent the mean±s.d. (n=3). Scale bar, 25 μm. Statistical analysis were performed with unpaired Student’s t-test and significant results are indicated by ‘**’(P=0.0004) and ‘***’(P=0.0001). A same concentration (3 mg ml⁻¹) of total chorion extract from each sample was used for the MPD assay.