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J Bacteriol. 1979 May; 138(2): 523-529
Copyright © 1979, American Society for Microbiology. All Rights Reserved.

Light Effects in Yeast: Evidence for Participation of Cytochromes in Photoinhibition of Growth and Transport in Saccharomyces cerevisiae Cultured at Low Temperatures

Stanislaw Uaszewski, Theofanis Mamouneas¹, Win-Kuang Shen², Philip J. Rosenthal², John R. Woodward, Vincent P. Cirillo¹ and Leland N. Edmunds Jr²

¹ Department of Biochemistry State University of New York, Stony Brook, New York 11794
² Department of Biology, State University of New York, Stony Brook, New York 11794

ABSTRACT

Visible light of moderate intensity inhibits growth, respiration, protein synthesis, and membrane transport in bakers' yeast and has a deleterious effect on membrane integrity. The results of this study indicate that these effects require the presence of cytochromes b and a/a₃. The light sensitivities of growth rate and [¹⁴C]histidine uptake in wild-type rho⁺ Y185 and D225-5A strains of Saccharomyces cerevisiae were compared with those in a variety of mutants lacking cytochrome b or a/a₃ or both; a close correlation was found between the presence of these respiratory pigments and photosensitivity. Thus, strain TL5-3C, a nuclear petite lacking cytochromes b, a, and a₃, was resistant to light; strain GL5-6A, another nuclear petite having reduced amounts of cytochromes a and a₃, was partially resistant; strains MB127-20C and MB1-6C, nuclear petites lacking only cytochrome b, were also only partially resistant to light; whereas mutants containing all three cytochromes but having their respiratory chain either nonfunctional (strain ZK3-6B) or uncoupled (strain 18-27/t12) were fully sensitive to light. Finally, an equal-energy, broad-band action spectrum for the light inhibition of growth and transport indicated that blue light (408 nm) was most effective; these wavelengths correspond to the Soret region of the cytochrome absorption spectrum. The results suggest, therefore, that the yeast cytochromes b, a, and a₃ are the primary photoreceptors for the inhibitory effects of light and, perhaps, for other processes, such as the entrainment of biological rhythms in this species.

Present address: Microbiological Institute, Wrocaw University, 51-148 Wrocaw, Poland.

Present address: Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, England.

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