Photosensitivity of respiration in <i>Neurospora</i> mitochondria. A protective role for carotenoid

Ramadan-Talib, Z; Qc, John Prebble

doi:10.1042/bj1760767

Cited by 19 publications

(15 citation statements)

References 32 publications

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“…Redox reactions of cytochromes and cytochrome c oxidase activity were unaffected. Similar findings were also obtained by Ramadan‐Talib and colleagues2 in their studies on the effect of visible light on respiratory activity of isolated mitochondria from Neurospora crassa . Photosensitive sites in the flavoprotein dehydrogenases were also discovered.…”

Section: Introductionsupporting

confidence: 88%

Mitochondrial Reactive Oxygen Species Generation and Calcium Increase Induced by Visible Light in Astrocytes

Jou

Guo

et al. 2004

Annals of the New York Academy of Sciences

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Mitochondria contain photosensitive chromophores that can be activated or inhibited by light in the visible range. Rather than utilizing light energy, however, mitochondrial electron transport oxidation-reduction reaction and energy coupling could be stimulated or damaged by visible light. Our previous work demonstrated that reactive oxygen species (ROS) were generated in cultured astrocytes after visible laser irradiation. With confocal fluorescence microscopy, we found that ROS were generated mostly from mitochondria. This mitochondrial ROS (mROS) formation plays a critical role in photoirradiation-induced phototoxicity and apoptosis. In this study, we measured changes of mitochondrial calcium level ([Ca(2+)](m)) in cultured astrocytes (RBA-1 cell line) irradiated with blue light and examined the association between mROS formation and [Ca(2+)](m) level changes. Changes of intracellular ROS and [Ca(2+)](m) were visualized using fluorescent probes 2',7'-dichlorodihydrofluorescein (DCF), and rhod-2. After exposure to visible light irradiation, RBA-1 astrocytes showed a rapid increase in ROS accumulation particularly in the mitochondrial area. Increase in [Ca(2+)](m) was also induced by photoirradiation. The levels of increase in DCF fluorescence intensity varied among different astrocytes. Some of the cells generated much higher levels of ROS than others. For those cells that had high ROS levels, mitochondrial Ca(2+) levels were also high. In cells that had mild ROS levels, mitochondrial Ca(2+) levels were only slightly increased. The rate of increase in DCF fluorescence seemed to be close to the rate of rhod-2 fluorescence increase. There is a positive and close correlation between mitochondrial ROS levels and mitochondrial Ca(2+) levels in astrocytes irradiated by visible light.

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Section: Introductionsupporting

confidence: 88%

Mitochondrial Reactive Oxygen Species Generation and Calcium Increase Induced by Visible Light in Astrocytes

Jou

Guo

et al. 2004

Annals of the New York Academy of Sciences

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“…It has been shown that carotenoid protects ubiquinone from photodestruction in mitochondria (Ramadan-Talib and Prebble 1978). Ubiquinone is an essential cellular component, which is used as an ingredient in cosmetics and for medical applications (Kuzina and Cerda-Olmedo 2007 and references therein).…”

Section: Metabolic Pathways As Output Pathways Of Light Signalingmentioning

confidence: 99%

Light regulation of metabolic pathways in fungi

Tisch

Schmoll

2009

Appl Microbiol Biotechnol

226

190

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Light represents a major carrier of information in nature. The molecular machineries translating its electromagnetic energy (photons) into the chemical language of cells transmit vital signals for adjustment of virtually every living organism to its habitat. Fungi react to illumination in various ways, and we found that they initiate considerable adaptations in their metabolic pathways upon growth in light or after perception of a light pulse. Alterations in response to light have predominantly been observed in carotenoid metabolism, polysaccharide and carbohydrate metabolism, fatty acid metabolism, nucleotide and nucleoside metabolism, and in regulation of production of secondary metabolites. Transcription of genes is initiated within minutes, abundance and activity of metabolic enzymes are adjusted, and subsequently, levels of metabolites are altered to cope with the harmful effects of light or to prepare for reproduction, which is dependent on light in many cases. This review aims to give an overview on metabolic pathways impacted by light and to illustrate the physiological significance of light for fungi. We provide a basis for assessment whether a given metabolic pathway might be subject to regulation by light and how these properties can be exploited for improvement of biotechnological processes.

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“…The effect of such metabolic alterations on light sensitivity cannot be estimated at present, although studies with other types of auxotrophic strains might provide a way to delineate general effects on light sensitivity ofnutrient limitation. Possible effects mediated by mitochondrial flavoprotein dehydrogenases, which have been implicated in the photoinhibition ofrespiration (28), also should be considered.…”

Section: Discussionmentioning

confidence: 99%

Photoreception in Neurospora crassa: correlation of reduced light sensitivity with flavin deficiency.

Paietta¹,

Sargent²

1981

Proc. Natl. Acad. Sci. U.S.A.

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The effect of flavin deficiency on blue light responses in Neurospora crassa was studied through the use of two riboflavin mutants (rib-i and rib-2). The photoresponses assayed were the, suppression of circadian conidiation, the phase shifting of the circadian conidiation rhythm, and the induction of carotenoid synthesis. Physiological responses to blue light are known in a large number oforganisms. Examples include phototropism in coleoptiles of monocots (1) and sporangiophores of fungi (2), induction of carotenoid synthesis in fungi (3), and entrainment of circadian pupal emergence in fruit flies (4). The photoreceptor pigments involved remain unidentified but most ofthe available evidence supports the hypothesis that a flavin is acting as the photoreceptor for many of these blue light responses. This evidence (reviewed in refs. 5 and 6) includes (i) the similarity between the absorption spectrum of riboflavin and the action spectra of both the blue light responses and light-induced absorbance changes involving a b-type cytochrome and (ii) the effects on blue light responses of inhibitors such as phenylacetic acid and potassium iodide which interact with flavins.Spectrophotometric studies with whole cells and cell fractions suggest that a primary photoreception event for the fungus Neurospora crassa is a flavin-mediated reduction of a b-type cytochrome (7,8). Experiments supporting cytochrome b involvement have been done with a cytoplasmic mutant, poky, which exhibits a low.cytochrome b content, a decrease in blue light-induced absorbance changes, and a decreased sensitivity to light for the suppression of circadian conidiation (9, 10).One approach to elucidation ofthe nature ofa photoreceptor is to use a system in which the photoreceptor levels can be perturbed. Ifthe photoreceptor is indeed a flavin, then a decrease in photoreceptor levels should occur in the case ofa generalized flavin deficiency and might result in a decrease of light sensitivity. To detect this effect, one needs a system having a blue light response that can be monitored quantitatively and in which a flavin deficiency can be specifically induced. Riboflavin-requiring mutants have been isolated in Neurospora (11,12)

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Photosensitivity of respiration in Neurospora mitochondria. A protective role for carotenoid

Cited by 19 publications

References 32 publications

Mitochondrial Reactive Oxygen Species Generation and Calcium Increase Induced by Visible Light in Astrocytes

Mitochondrial Reactive Oxygen Species Generation and Calcium Increase Induced by Visible Light in Astrocytes

Light regulation of metabolic pathways in fungi

Photoreception in Neurospora crassa: correlation of reduced light sensitivity with flavin deficiency.

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