Fig. 1. Effects of the wild-type (A-C) and the P446L mutant importin-ß (D-F) following their injection, along with a fluorescent nuclear substrate, into wild-type cleavage embryos. Arrows show the site of injection. Import of the fluorescent nuclear substrate into the nuclei was followed in a laser-scanning microscope. The A and D, the B and E and the C and F photographs were taken at roughly identical stages of the cleavage cycles. The few nuclei shown on F appeared following diffusion of the fluorescent substrate away from the site of injection. Bar, 100 µm.