Summary
Actinomycin-D inhibits phytochrome-mediated responses of etiolated plants. In the unrolling response of a barley first leaf the inhibition by act. D is greater when the antibiotic is applied 80 minutes after irradiation; earlier or later applications are less inhibitory. Inhibition is relieved by deoxyguanosine applied before or after act. D. Similar effects are found with the plumular hooks of peas and beans. These results suggest that phytochrome-mediated responses involve RNA production on a DNA template. The location of phytochrome in the cell is discussed in relation to its possible association with DNA, especially that of the plastids and mitochondria. Phytochrome may thus act as a repressor of gene sequences involved (for instance) in the removal of etiolation symptoms, red light (660 nm) causing its dissociation from DNA. Far-red radiation may reverse the effects by causing re-association of phytochrome.
Zusammenfassung
Actinomycin D vermag verschiedene phytochromgesteuerte Reaktionen etiolierter Pflanzen zu hemmen. So wird z. B. die von Rotlicht induzierte Aufrollung des ersten Blattes von im Dunkeln kultivierter Gerste besonders durch Act. D gehemmt, wenn man das Antibioticum ungefähr 80 min nach der Belichtung appliziert; spätere oder frühere Darbietung wirkt weniger oder überhaupt nicht. Die Hemmung wird durch Desoxyguanosin aufgehoben.
Unter Berücksichtigung der bekannten Aktionsweise des Actinomycins D bei der DNS-abhängigen RNS-Synthese und der aus der Literatur bisher bekannten Tatsachen über phytochromgesteuerte Reaktionen muß vermutet werden, daß das Phytochrom eng an das DNS gebunden ist (vermutlich auch in Plastiden und Mitochondrien!) und als Repressor-System fungiert. Rotlicht löst diese Bindung und ermöglicht dadurch die Gen-Wirkung.
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D. M. Reid is the holder of an Agricultural Research Council Post-Graduate Studentship.
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Carr, D.J., Reid, D.M. Actinomycin-D inhibition of phytochrome-mediated responses. Planta 69, 70–78 (1966). https://doi.org/10.1007/BF00380212
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DOI: https://doi.org/10.1007/BF00380212