Light Availability Influences psbA Expression and the Ratio of Two Forms of D1 in Cyanobacterial Thylakoids

Schaefer, Michael; Bustos, Silvia A.; Golden, Susan S.

doi:10.1007/978-94-009-0511-5_418

Cited by 31 publications

(54 citation statements)

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“…The levels ofpsbAII andpsbAIII transcripts increase 2-to 10-fold within minutes after cells are shifted to high light intensity (6,32). Translational fusions to each of these genes indicate that either transcription or translation increases dramatically when the PPFD is high (35).…”

Section: Discussionmentioning

confidence: 99%

“…Immunoblot analysis of membrane proteins from wild-type cultures shows that the ratio of the two forms of Dl in the thylakoid changes, as predicted by reporter gene activities (34 (32). Increases in overall psbA message levels stimulated by higher light intensities have been reported for Synechococcus sp.…”

mentioning

confidence: 81%

“…Each of the genes encodes an open reading frame of 360 amino acids which is highly conserved with the 353-residue polypeptide encoded by chloroplastpsbA genes. The psbAI gene encodes form I of the Dl protein, whereas both psbAII and psbAIII encode form II (13,32). A functional difference between the two forms, which differ at 25 residues, has not been determined.…”

mentioning

confidence: 99%

“…The three Synechococcus psbA genes are differentially expressed and respond to changes in light intensity (6,34,35). This was initially demonstrated by measuring ,-galactosidase activities in strains that carry specific psbA-lacZ translational fusions recombined into the Synechococcus chromosome.…”

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confidence: 99%

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Transcriptional and posttranscriptional components of psbA response to high light intensity in Synechococcus sp. strain PCC 7942

1992

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The psbA genes, which encode the Dl protein of photosystem II, constitute a multigene family in the cyanobacterium Synechococcus sp. strain PCC 7942. Levels of messages from the three psbA genes change rapidly when cells are shifted from low-light to high-light conditions: the psbAI message level drops, whereas psbAII and psbAIII message levels increase dramatically. We examined the potential contributions of transcriptional and posttranscriptional processes in these high-light responses by subjecting cells that had been grown in a turbidostat at a standard light intensity (130 microeinsteins [1±EJ m-2 s-') to either the same or a higher light intensity (500 ,uE m-2 s-') in the presence or absence of rifampin. Northern (RNA blot) analysis of RNA isolated from cells subjected to high light showed that the increases in psbAII and psbAIII transcripts were blocked by rifampin. This suggests a transcriptional induction of these genes at high light intensities.Increased mRNA stability does not contribute to their accumulation in high-light conditions, since their half-life values did not increase relative to the half-lives measured at the standard light intensity. The rate of disappearance of the psbAI transcript in cells shifted to high light was diminished when either transcription or translation was blocked by rifampin or chloramphenicol, suggesting that accelerated degradation of the message requires de novo synthesis of a protein factor. When rifampin was added 10 min after the shift to high light intensity rather than before the shift, psbAl and psbAIII messages, but not the psbAII message, decayed at a faster rate. Susceptibility of the psbAIII transcript to the high-light-induced factor was also demonstrated by addition of chloramphenicol prior to the shift to high light. psbAIII transcript levels went up more than twofold higher in chloramphenicol-treated cells than in untreated cells, whereas psbAII transcript levels were unaffected by the inhibitor. These experiments provide evidence that either new or increased synthesis of a degradation factor which affects a subset of Synechococcus transcripts occurs in cells subjected to high light intensity.

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Section: Discussionmentioning

confidence: 99%

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confidence: 81%

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confidence: 99%

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Transcriptional and posttranscriptional components of psbA response to high light intensity in Synechococcus sp. strain PCC 7942

1992

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“…If v-D1 and host D1 are fully functional in the PSII reaction center, why would there be a selection for different variants in the two lineages, particularly when there is evidence of recombination at the nucleotide level over evolutionary time? Sullivan et al (2006) suggested that v-D1 sequences of Synechococcuslike phages are more similar to Form II of D1, which is known in freshwater strains to be a high-light and stress-induced variant, than to 'housekeeping' Form I encoded by the Synechococcus species (Schaefer and Golden, 1989;Clarke et al, 1993). We propose that like host Form II, v-D1 is less susceptible to photodamage and turnover than the host D1, a feature that could be important for 'life support' during the short period of phage morphogenesis.…”

Section: Potential Ecological Implicationsmentioning

confidence: 99%

Viral photosynthetic reaction center genes and transcripts in the marine environment

et al. 2007

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Cyanobacteria of the genera Synechococcus and Prochlorococcus are important contributors to photosynthetic productivity in the open ocean. The discovery of genes (psbA, psbD) that encode key photosystem II proteins (D1, D2) in the genomes of phages that infect these cyanobacteria suggests new paradigms for the regulation, function and evolution of photosynthesis in the vast pelagic ecosystem. Reports on the prevalence and expression of phage photosynthesis genes, and evolutionary data showing a potential recombination of phage and host genes, suggest a model in which phage photosynthesis genes help support photosynthetic activity in their hosts during the infection process. Here, using metagenomic data in natural ocean samples, we show that about 60% of the psbA genes in surface water along the global ocean sampling transect are of phage origin, and that the phage genes are undergoing an independent selection for distinct D1 proteins. Furthermore, we show that different viral psbA genes are expressed in the environment.

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Electron transport regulates exchange of two forms of photosystem II D1 protein in the cyanobacterium Synechococcus.

et al. 1995

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Synechococcus sp. PCC 7942 modulates photosynthetic function by transiently replacing the constitutive D1 photosystem II protein, D1:1, with an alternate form, D1:2, to help counteract photoinhibition under excess light. We show that a temperature drop from 37 to 25 degrees C also drives D1:1/D1:2 exchange under constant, moderate light. Chilling or light‐induced D1 exchange results from rapid loss of psbAI message coding for D1:1 and accumulation of psbAII and psbAIII messages coding for D1:2. During chilling, a large pool of a novel form, D1:2*, transiently accumulates, distinguishable from normal D1 by an increase in apparent molecular mass. D1:2* is not phosphorylated and is probably a functionally inactive, incompletely processed precursor. After acclimation to 25 degrees C, D1:2* disappears and D1:1 again predominates, although substantial D1:2 remains. Partial inhibition of electron transport under constant, moderate light also triggers the D1 exchange process. These treatments all increase excitation pressure on photosystem II relative to electron transport. Therefore, information from photosynthetic electron transport regulates D1 exchange without any requirement for a change in light intensity or quality, possibly via a redox sensing mechanism proximal to photosystem II.

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Light Availability Influences psbA Expression and the Ratio of Two Forms of D1 in Cyanobacterial Thylakoids

Cited by 31 publications

References 4 publications

Transcriptional and posttranscriptional components of psbA response to high light intensity in Synechococcus sp. strain PCC 7942

Transcriptional and posttranscriptional components of psbA response to high light intensity in Synechococcus sp. strain PCC 7942

Viral photosynthetic reaction center genes and transcripts in the marine environment

Electron transport regulates exchange of two forms of photosystem II D1 protein in the cyanobacterium Synechococcus.

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