Modified cryptochrome in vivo absorption in dim photosporulation mutants of Trichoderma.

Mutants of Trichoderma harzianum that are defective in blue-light-induced sporulation were induced by nutritional stresses as an alternative to light. These mutants may be modified in the putative photoreceptor pigment "cryptochrome" or in an early transduction component. dim (dimsighted) mutants induced by a short transient stress were mapped into four complementation groups and were chosen for study of pigment deficiencies by in vivo absorption spectroscopy. Mutants rib(-)10 and lys(-)44 in the dimY complementation group had altered in vivo absorption spectra in the blue region. Difference spectra obtained by subtracting dimY spectra from that of the wild type had difference bands with peaks at 455 and 480 nm. The similarity between the in vivo difference spectra and the action spectrum for sporulation in wild-type Trichoderma suggests that the mutants lack cryptochrome or have a defective cryptochrome. The decrease in photoresponse as well as the modification of the action spectrum near 480 nm in a dimY mutant support these suggestions. Both dimY mutants pleiotropically accumulate a yellow water-soluble pigment absorbing at wavelengths lower than the blue maxima of cryptochrome; this yellow pigment may be related to cryptochrome.