Trends in Genetics
ForumTightening the Screws on PsbA in Cyanobacteria
Section snippets
The Relevance of psbA Regulation in Cyanobacteria
PSII is the water-splitting (oxygen-evolving) enzyme of photosynthesis. Among PSII core proteins, the D1 subunit (encoded by the psbA gene) provides most of the ligands for the water-splitting cluster involved in primary charge separation and evolution of molecular oxygen. This oxidative chemistry causes excessive light-induced photodamage to the D1 subunit than to any other core protein. Therefore, the expression of D1 protein is stringently regulated in photoautotrophs and exhibits a high
Sigma-Factor-Mediated Regulation of psbA Gene Expression
Specific promoter recognition by RNA polymerase and transcription initiation relies on sigma factor proteins in prokaryotes [3., 4., 5., 6.]. The expression of cyanobacterial psbA genes and their light-responsive nature is regulated by the housekeeping sigma factor and alternative sigma factors respectively (Figure 1A). Mutants of Synechocystis lacking sigma factor SigD and SigB display considerably less accumulation of psbA2/psbA3 transcripts after 45 min of high light exposure, whereas the
D1 Regulation through Response Regulators and Histidine Kinases
The expression of photosynthetic genes is believed to be regulated by an altered redox state of the electron transport chain, perceived by sensory regulators in cyanobacteria. The putative histidine kinase, NblS, is one such regulator that is found to control the expression of psbA genes by a blue/UV-light and high-light stimulus in Synechococcus [8]. The deletion of nblS gene in Synechococcus results in the elimination of light-mediated regulation of all psbA genes [9]. Interestingly, a PAS
Impact of Transcriptional and Post-transcriptional Effectors on psbA Expression
The cmpABCD operon, encoding a high-affinity bicarbonate transporter, is induced under high-light and low-CO2 conditions by a LysR family protein, CmpR in Synechococcus [14]. The binding sites of CmpR are also present in the promoter regions of the genes, psbAII and psbAIII, and shown to be responsive to high light and low CO2. However, upon loss of cmpR, both genes are still induced under the above conditions, suggesting the involvement of more than one mechanism and additional transcriptional
Concluding Remarks
Being the most iconic subunit of photosystems, D1 has been studied extensively, resulting in the accumulation of a large amount of data regarding its structure, function, and evolution. Two recent findings concerning D1 proteins are breakthrough in contemporary photosynthetic research: (i) the role of a highly divergent D1 in chlorophyll f biosynthesis in cyanobacteria equipped with a sophisticated FarLiP (far-red light photoacclimation) gene cluster; and (ii) improved heat resistance by a
Acknowledgments
We are grateful for all the colleagues whose work is cited or could not be cited in this Forum. We extend our apology to the authors whose important work is not mentioned here owing to word and citation constraints. We are thankful to Dr Michael Reppert (Purdue University, USA) for reading the manuscript and providing useful comments. The infrastructural support from the Department of Science and Technology, New Delhi, Govt. of India, through FIST grant (Grant No. 1196 SR/FST/LS-I/ 2017/4) and
References (26)
Strategies for psbA gene expression in cyanobacteria, green algae and higher plants: from transcription to PSII repair
Biochim. Biophys. Acta Bioenerg.
(2012)Induction of a group 2 σ factor, RPOD3, by high light and the underlying mechanism in Synechococcus elongatus PCC 7942
J. Biol. Chem.
(2007)One day of nitrogen starvation reveals the effect of sigE and rre37 overexpression on the expression of genes related to carbon and nitrogen metabolism in Synechocystis sp. PCC 6803
J. Biosci. Bioeng.
(2015)Alterations in global patterns of gene expression in Synechocystis sp. PCC 6803 in response to inorganic carbon limitation and the inactivation of ndhR, a LysR family regulator
J. Biol. Chem.
(2004)The diversity and distribution of D1 proteins in cyanobacteria
Photosynth. Res.
(2020)- et al.
An RpaA-dependent sigma factor cascade sets the timing of circadian transcriptional rhythms in Synechococcus elongatus
Cell Rep.
(2018) Simultaneous inactivation of sigma factors B and D interferes with light acclimation of the cyanobacterium Synechocystis sp. strain PCC 6803
J. Bacteriol.
(2009)6S RNA plays a role in recovery from nitrogen depletion in Synechocystis sp. PCC 6803
BMC Microbiol.
(2017)Control of photosynthetic and high-light-responsive genes by the histidine kinase DspA: negative and positive regulation and interactions between signal transduction pathways
J. Bacteriol.
(2004)nblS, a gene involved in controlling photosynthesis-related gene expression during high light and nutrient stress in Synechococcus elongatus PCC 7942
J. Bacteriol.
(2002)
Consequences of a deletion in dspA on transcript accumulation in Synechocystis sp. strain PCC6803
J. Bacteriol.
Negative control of the high light-inducible hliA gene and implications for the activities of the NblS sensor kinase in the cyanobacterium Synechococcus elongatus strain PCC 7942
Arch. Microbiol.
A redox-responsive regulator of photosynthesis gene expression in the cyanobacterium Synechocystis sp. strain PCC 6803
J. Bacteriol.
Cited by (4)
The use of RNA-based treatments in the field of cancer immunotherapy
2023, Molecular Cancer