Action Spectrum for Enzymatic Photoreactivation in Maize*

An ammonium‐sulfate‐precipitable (35–70 per cent) fraction in extracts of Zea mays pollen contains photoreactivating enzyme that reactivates the transforming ability of ultraviolet‐inactivated Hemophilus influenzae DNA. The action spectrum of in vitro photoreactivation with the enzyme has a broad single maximum at 385 nm. Parallel to the in vitro response, in vivo photo‐reactivation of ultraviolet‐induced premutational damage in pollen of this plant is more efficient at 405 nm than at 334 nm. From these results we conclude that photoreactivation of ultraviolet‐induced mutational damage in maize pollen is chiefly of the direct enzymatic type.