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Plant Physiology 81:726-730 (1986)
© 1986 American Society of Plant Biologists

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Articles

Modified Light-Induced Absorbance Changes in dim Y Photoresponse Mutants of Trichoderma1

Benjamin A. Horwitz2, Chafia H. Trad and Edward D. Lipson

Department of Physics, Syracuse University, Syracuse, New York 13244-1130

A brief pulse of blue light induces the common soil fungus Trichoderma harzianum to sporulate. Photoresponse mutants with higher light requirements than the wild type are available, including one class, dim Y, with modified absorption spectra. We found blue-light-induced absorbance changes in the blue region of the spectrum, in wild-type and dim Y mutant strains. The light-minus-dark difference spectra of the wild type and of several other strains indicate photoreduction of flavins and cytochromes, as reported for other fungi and plants. The difference spectra in strains with normal photoinduced sporulation have a prominent peak at 440 nm. After actinic irradiation, this 440 nanometer difference peak decays rapidly in the dark. In two dim Y photoresponse mutants, the difference spectra were modified; in one of these, LS44, the 440 nanometer peak was undetectable in difference spectra. Detailed study of the dark-decay kinetics in LS44 and the corresponding control indicated that the 440 nanometer difference peak escaped detection in LS44 because it decays faster than in the control. The action spectrum of the 440 nm difference peak is quite different from that of photoinduced sporulation. The light-induced absorbance changes are thus unlikely to be identical to the primary photochemical reaction triggering sporulation. Nevertheless, these results constitute genetic evidence that physiologically relevant pigments participate in these light-induced absorbance changes in Trichoderma.

2 Present address: Carnegie Institution of Washington, Department of Plant Biology, 290 Panama St., Stanford, CA 94305-1297.

1 Supported by National Science Foundation grant DMB-8316458 to E.D.L. B.A.H. was supported by a Weizmann Postdoctoral Fellowship.






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ASPB Publications PLANT PHYSIOLOGY THE PLANT CELL
Copyright © 1986 by the American Society of Plant Biologists