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LIGHT EFFECTS IN YEAST : PERSISTING OSCILLATIONS IN CELL DIVISION ACTIVITY AND AMINO ACID TRANSPORT IN CULTURES OF SACCHAROMYCES CEREYISIAE ENTRAINED BY LIGHT‐DARK CYCLES *
Author(s) -
Edmunds Leland N.,
Apter Ray I.,
Rosenthal Philip J.,
Shen WinKuang,
Woodward John R.
Publication year - 1979
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.1751-1097.1979.tb07186.x
Subject(s) - circadian rhythm , biology , darkness , ultradian rhythm , entrainment (biomusicology) , saccharomyces cerevisiae , biophysics , yeast , cell division , light intensity , biochemistry , microbiology and biotechnology , rhythm , medicine , endocrinology , botany , cell , optics , physics
Abstract— In addition to the direct inhibitory effects of visible light (cool‐white fluorescent, < 3500 lux) on growth and amino acid transport previously reported for cultures of the yeast Saccharomyces cereui‐siae (strain Y185 rho + ) grown at 12°C in medium containing glucose, yeast carbon base, KH 2 PO 4 , ammonium ion and proline, we have found evidence for endogenous, light‐entrainable, self‐sustaining circadian and ultradian oscillators underlying both cell division and transport activity. Diurnal light (⋍ 3000 lux) cycles (LD), imposed on cultures previously grown in the dark, phased or synchronized cell number increase to a 24‐h period with bud release being confined primarily to the dark intervals (although not necessarily every cell divided during any given division ‘burst’). The observed division or budding rhythm freeran with a circadian period (⋍26h) only approximating 24 h for a number of days in constant darkness (DD) following prior entrainment by LD, thereby implicating an endogenous circadian clock. Further, a similar light‐entrainable circadian rhythm in the uptake of “C‐histidine or 1 4C‐lysine occurred in nondividing (or very slowly dividing) cultures during the “stationary” (infradian) phase of growth synchronized by a 24‐h LD cycle and then released into DD for as long as 10 days. Some experiments revealed a bimodal (ultradian) periodicity in both LD and DD with secondary peaks or shoulders occurring at intervals of ⋍12h, corresponding approximately to subjective ‘dawn’ and ‘dusk’. Transport in cultures of the Y185 rho ‐ petite mutant, which lacks cytochromes a/a 3 , b and c l , could not be synchronized by LD cycles, a finding that is consistent with the hypothesis that these chromophores may be primary photoreceptors for synchronization of rhythms in this microorganism.