Photoreactivation Action Spectrum of Tobacco Mosaic Virus‐ribonucleic Acid Inactivated by U.V. Radiation*

Abstract

Abstract— Initially photoreactivation of irradiated (2537 Å) nucleic acid on pinto bean increases linearly with time of illumination with white light of 250 ft‐c. Maximum amounts of photo‐reactivation depend on the quality of light used. The action spectrum shows a peak in the ‘black light’ region, where the greater amount of photoreactivation is found, and a shoulder in the blue light region. Maximum repair is obtained with ‘black light.’ Photoreactivation does not occur at wavelengths above 550 nm. Photoprotection by illumination of leaves prior to inoculation by irradiated RNA was not found. The action spectrum for photoreactivation does not resemble the action spectrum for photosynthesis.

IN VITRO PHOTOREACTIVATION OF ULTRAVIOLET‐INACTIVATED RIBONUCLEIC ACID FROM TOBACCO MOSAIC VIRUS

“…Per cent survivals are given with average deviations from the means calculated from the response of each plant. Photorecoveries in these experiments vary from 14 to 46 per cent and are in the range observed in vivo (Hidalgo-Salvatierra and McLaren, 1969). A trend is clear, but statistical variations are large.…”

“…Xanthi, n.c., a local lesion host for TMV-RNA, in which in vivo photoreactivation of TMV-RNA has been repeatedly demonstrated (Rushizky e f al., 1960;McLaren, 1968;Murphy and Gordon, 1971a, b;Gordon et al, 1974). The wavelength used in these experiments was the one found to be most effective in vivo (Hidalgo-Salvatierra and McLaren, 1969;Murphy and Gordon, 1971a). Boiling of the Xanthi extracts destroys all detectable activity, which supports the existence of a postulated enzyme-mediated photoreactivation of UVinactivated viral RNA.…”

“…All four solutions were then kept in an ice bath. Samples were inoculated onto leaves of pinto bean plants (Hidalgo-Salvatierra and McLaren, 1969) in a black room under red light. The carborundum, an aid to inoculation, was then washed off the plants.…”