INTERACTION BETWEEN PHYTOCHROME AND THE BLUE-LIGHT PHOTORECEPTOR SYSTEM IN MOUGEOTIA - TEMPERATURE-DEPENDENCE

The interaction between cryptochrome and phytochrome, the pigments con trolling the face-to-profile movement of Mougeotia chloroplasts, was i nvestigated at 2 degrees C. The response was induced with blue, follow ed by red, light flashes of approximately 6 ms. After a dark period re quired for interaction, the remaining P-fr gradient was cancelled with far-red light. The delay between the blue and red flashes was varied to study the effect of low temperature on the lifetime of the hypothet ical blue signal carrier generated in the cryptochrome-mediated reacti on. The Q(10) quotient of 2.7-3.0 was calculated from the delay curves measured at 17 and 2 degrees C, The interaction between the blue sign al carrier and P-fr proceeded effectively at 2 degrees C and reached a maximum after 10 min. Contrary to previously reported results, the te mperature of 2 degrees C did not block the phytochrome-mediated profil e-to-face movement induced by red light flashes or continuous irradiat ion. (C) 1997 Elsevier Science S.A.