Coordinate up‐regulation of carotenoid biosynthesis as a response to light stress in <i>Synechococcus</i> PCC7942

The vast majority of oxygenic photosynthetic organisms use monovinyl chlorophyll for their photosynthetic reactions. For the biosynthesis of this type of chlorophyll, the reduction of the 8-vinyl group that is located on the B-ring of the macrocycle is essential. Previously, we identified the gene encoding 8-vinyl reductase responsible for this reaction in higher plants and termed it DVR. Among the sequenced genomes of cyanobacteria, only several Synechococcus species contain DVR homologues. Therefore, it has been hypothesized that many other cyanobacteria producing monovinyl chlorophyll should contain a vinyl reductase that is unrelated to the higher plant DVR. To identify the cyanobacterial gene that is responsible for monovinyl chlorophyll synthesis, we developed a bioinformatics tool, correlation coefficient calculation tool, which calculates the correlation coefficient between the distributions of a certain phenotype and genes among a group of organisms. The program indicated that the distribution of a gene encoding a putative dehydrogenase protein is best correlated with the distribution of the DVR-less cyanobacteria. We subsequently knocked out the corresponding gene (Slr1923) in Synechocystis sp. PCC6803 and characterized the mutant. The knock-out mutant lost its ability to synthesize monovinyl chlorophyll and accumulated 3,8-divinyl chlorophyll instead. We concluded that Slr1923 encodes the vinyl reductase or a subunit essential for monovinyl chlorophyll synthesis. The function and evolution of 8-vinyl reductase genes are discussed.Chlorophyll is an essential molecule that is utilized in photosynthetic reactions (1). Various chlorophyll species exist among photosynthetic organisms. Anoxygenic photosynthetic bacteria contain bacteriochlorophyll a, b, c, d, e, and g (2), and oxygenic photosynthetic organisms such as cyanobacteria, algae, and land plants produce chlorophyll a, b, c, d and 3,8-divinyl chlorophyll a 3 and b ( Fig. 1) (3, 4). Among them, the biosynthesis of chlorophyll a, b, c, d and all bacteriochlorophyll species requires the reduction of the 8-vinyl group (2). All of these chlorophyll molecules have a common backbone structure. Modification of the side chains on the common backbone structure gives rise to the diversity of chlorophylls (5, 6). Among the variety of chlorophyll species, bacteriochlorophyll a and monovinyl chlorophyll a (Fig. 1) are most commonly used for the photochemistry in photosynthetic organisms. The exceptions to this are a group of marine cyanobacteria, Prochlorococcus species (7), and a cyanobacterial symbiont, Acaryochloris marina (8), which use 3,8-divinyl chlorophyll a (Fig. 1) and chlorophyll d for their photochemistry, respectively. It is not clear why the majority of photosynthetic organisms prefer monovinyl chlorophylls instead of divinyl chlorophyll species. Akimoto et al. (9) recently suggested that the replacement of monovinyl chlorophylls by 3,8-divinyl chlorophylls in the dvr mutant of Arabidopsis thaliana significantly changed the antenna system and t...

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“…This carotenoid species protects cells from photoinhibition (32,33). The level of zeaxanthin increases by strong illumination (32).…”

Section: Journal Of Biological Chemistrymentioning

confidence: 99%

Identification of a Novel Vinyl Reductase Gene Essential for the Biosynthesis of Monovinyl Chlorophyll in Synechocystis sp. PCC6803

Itô¹,

Yokono²,

Tanaka

et al. 2008

Journal of Biological Chemistry

112

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“…As effective quenchers of triplet-state photosensitizers, singlet oxygen, and peroxy radicals, carotenes have been proven to be effective against UV damage in organisms that suffer photooxidative stress (Albrecht et al, 2001;Lakatos et al, 2001;Laurion et al, 2002). For example, it has been reported that carotenes can provide significant protection against UVB in the cyanobacterium Synechococcus PCC7942 (Gotz et al, 1999;Schafer et al, 2006) and in Dunaliella spp. (White and Jahnke, 2002).…”

Section: Discussionmentioning

confidence: 99%

Raman Spectroscopic Analysis of a Desert Cyanobacterium Nostoc sp. in Response to UVB Radiation

et al. 2010

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Cyanobacteria are capable of tolerating environmental extremes. To survive in extreme environments, cyanobacteria have developed the capability to adapt to a variety of stresses. For example, cyanobacteria have adopted a number of strategies with which to survive UV stress, including expression of UV-screening pigments and antioxidant systems. We have previously shown that several antioxidants are significantly expressed in Nostoc sp. by UVB irradiation. We report here that the content of UV-responsive biomarkers such as b-carotene and scytonemin can be easily detected by Fourier transform Raman spectroscopy with use of a small sample size and that the content of b-carotene is dependant on the UVB intensity and exposure time. Our results indicate that Raman spectroscopy may be a helpful tool to analyze UV-protective molecules of cyanobacterium in astrobiological studies without access to large sample sizes and complicated extractions, which are needed by other analytical techniques such as high-performance liquid chromatography and mass spectrometry.

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“…In wild type, a strong increase of the transcripts of all carotenogenic genes was observed, in contrast to the ntcA transcript which did not change significantly (data not shown). For crtW, transcript level was seven-fold higher after 6 h treatment and 15 fold higher after 24 h. The increase of the crtO transcript was slower but reached a similar relative increase after 24 h. The crtB gene is light-regulated in other cyanobacteria [9,10]. Therefore, we also looked for transcription changes of this gene.…”

Section: Transcript Changes Upon High-light Treatmentmentioning

confidence: 99%

“…Photo protection is an invasive process which may lead to lower carotenoid pools under high light through photo oxidation which up-regulated biosynthesis cannot fully compensate [7]. Increase of carotenoid biosynthesis under high-light conditions is caused by an up-regulation of the promotor of crtB in different zeaxanthin accumulating cyanobacteria [8,9]. This gene encodes phytoene synthase, the gateway enzyme of the specific carotenoid pathway.…”

Section: Introductionmentioning

confidence: 99%

Control of light-dependent keto carotenoid biosynthesis inNostoc7120 by the transcription factor NtcA

Sandmann

Mautz

Breitenbach

2016

Zeitschrift Für Naturforschung C

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Abstract:In Nostoc PCC 7120, two different ketolases, CrtW and CrtO are involved in the formation of keto carotenoids from β-carotene. In contrast to other cyanobacteria, CrtW catalyzes the formation of monoketo echinenone whereas CrtO is the only enzyme for the synthesis of diketo canthaxanthin. This is the major photo protective carotenoid in this cyanobacterium. Under high-light conditions, basic canthaxanthin formation was transcriptionally up-regulated. Upon transfer to high light, the transcript levels of all investigated carotenogenic genes including those coding for phytoene synthase, phytoene desaturase and both ketolases were increased. These transcription changes proceeded via binding of the transcription factor NtcA to the promoter regions of the carotenogenic genes. The binding was absolutely dependent on the presence of reductants and oxo-glutarate. Light-stimulated transcript formation was inhibited by DCMU. Therefore, photosynthetic electron transport is proposed as the sensor for high-light and a changing redox state as a signal for NtcA binding.

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Coordinate up‐regulation of carotenoid biosynthesis as a response to light stress in Synechococcus PCC7942

Cited by 48 publications

References 35 publications

Identification of a Novel Vinyl Reductase Gene Essential for the Biosynthesis of Monovinyl Chlorophyll in Synechocystis sp. PCC6803

Identification of a Novel Vinyl Reductase Gene Essential for the Biosynthesis of Monovinyl Chlorophyll in Synechocystis sp. PCC6803

Raman Spectroscopic Analysis of a Desert Cyanobacterium Nostoc sp. in Response to UVB Radiation

Control of light-dependent keto carotenoid biosynthesis inNostoc7120 by the transcription factor NtcA

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