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INDUCTION OF Trichoderma SPORULATION BY NANOSECOND LASER PULSES: EVIDENCE AGAINST CRYPTOCHROME CYCLING
Author(s) -
Horwitz Benjamin A.,
Perlman Alexander,
Gressel Jonathan
Publication year - 1990
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1990.tb01689.x
Subject(s) - action spectrum , phytochrome , laser , nanosecond , phototaxis , irradiation , fluence , photobleaching , chemistry , cryptochrome , materials science , biophysics , optics , photochemistry , botany , biology , physics , red light , fluorescence , biochemistry , gene , nuclear physics , circadian clock
— An important question in the study of photoreceptor action in morphogenesis is whether the chromophore is unidirectionally photobleached, or whether it is recycled, allowing each receptor molecule to be counted more than once. The common soil fungus Trichoderma harzianum grows vegetatively in the dark and sporulates in response to a pulse of blue or UV‐A light. Colonies were grown at 26 o C, transferred to 3 o C, illuminated with non‐saturating light, and then put back at 26 o C to sporulate. The fluence‐response curves for photoinduction in the cold and at 26 o C were identical, indicating that there are no enzymatic transduction processes during irradiation. Regions of the perimeter of dark‐grown colonies were given single pulses (maximum duration, 30 ns) at 355 nm with a neodymium laser. We obtained a complete fluence‐response curve for the laser pulses, which agreed with data for irradiations in the second to minute range. Photoinduction at 3 o C, and validity of Bunsen‐Roscoe reciprocity from nanoseconds to minutes, support the hypothesis that the inductive event is a simple first‐order photobleaching reaction.