Induction of embryonic SA-β-gal activity by oxidative stress. (A–D) Embryos treated with 500 μM BHP from 6 hpf to 6 dpf (B) have higher SA-β-gal activity than untreated embryos (A). Plots of the colorimetric quantitation of SA-β-gal staining show a near-linear increase of SA-β-gal activity with increased oxidative stress by BHP (C) or hydrogen peroxide (H2O2) (D). (E) Catalase overexpression can reduce SA-β-gal induction in embryos treated with moderate amounts of oxidative stress. Embryos injected with 300 pg of catalase mRNA at the one cell stage show significantly less SA-β-gal activity at 6 dpf than those injected with a control mRNA following incubation with 350 μM BHP from 6 hpf to 6 dpf. (F) Knockdown of endogenous catalase sensitizes embryos to oxidative stress-dependent SA-β-gal induction. Embryos injected with 8 ng of an antisense morpholino (MO) for catalase show a significant increase in SA-β-gal activity at 6 dpf when stressed with 350 μM BHP from 6 hpf to 6 dpf. *P<0.05 (Student t-test).
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