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MYCOCHROME SYSTEM AND CONIDIAL DEVELOPMENT IN CERTAIN FUNGI IMPERFECTI
Author(s) -
Kumagai Tadashi
Publication year - 1978
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.1751-1097.1978.tb07615.x
Subject(s) - blue light , absorbance , conidium , botrytis cinerea , irradiation , pigment , photolyase , chemistry , mycelium , photochemistry , conidiation , botany , biology , materials science , chromatography , optoelectronics , biochemistry , organic chemistry , physics , gene , nuclear physics , mutant , dna repair
Abstract. A photoreceptor system, “mycochrome”, is involved in a blue and near UV reversible photo‐reaction which in turn plays an important role in the photocontrol of conidial development in Alternaria tomato, Botrytis cinerea and Helminthosporium oryzae . Conidial development was controlled by alternating exposures to blue and near UV light with the final response being determined by the final light received. When the final light was near UV a conidium developed; when it was blue, conidiation was inhibited and a “sterile” conidiophore was formed. The effects of the two lights were alternatively reversible. Blue and near UV reversible photoreaction was also found in a light‐minus‐dark difference spectrum of an intracellular particulate fraction isolated from dark‐grown mycelia of A. tomato , and two pigments, P B (blue absorbing type) and P NUV (near UV absorbing type), were contained in that photoreaction. P B was tightly bound to the particulate fraction and P NUV was either soluble in the cytoplasm or very loosely bound to the particulate fraction. Blue and near UV reversible photoreaction occurred only under the coexistence of P B and P NUV . That is, a dip in the near UV region and peak absorbance in the blue region was induced by irradiation with near UV light; however, both conditions were partially dissipated with a subsequent irradiation of blue light. These absorbance changes were revers‐ibly repeated by alternating doses of blue and near UV light. When molecular oxygen was introduced after exposure to near UV light, peak absorbance in the blue region rapidly disappeared, and these absorbance changes were repeatedly reversible. Similar results were obtained by treatment with sodium hydrosulfite and molecular oxygen. Thus, it was concluded that the mycochrome system suggested in photo‐conidiation was consistent with certain active substances showing blue and near UV reversible absorbance changes and caused by photooxidation reduction reaction.