Differential expression of antenna and core genes in Prochlorococcus PCC 9511 (Oxyphotobacteria) grown under a modulated light-dark cycle

The continuous changes in incident solar light occurring during the day oblige oxyphototrophs, such as the marine prokaryote Prochlorococcus, to modulate the synthesis and degradation rates of their photosynthetic components finely. How this natural phenomenon influences the diel expression of photo...

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Published in:Environmental microbiology 2001-03, Vol.3 (3), p.168-175
Main Authors: Garczarek, Laurence, Partensky, Frédéric, Irlbacher, Horst, Holtzendorff, Julia, Babin, Marcel, Mary, Isabelle, Thomas, Jean Claude, Hess, Wolfgang R.
Format: Article
Language:English
Subjects:
Bacterial Proteins
Bacterial Proteins - genetics
Base Sequence
Cyanobacteria
Cyanobacteria - cytology
Cyanobacteria - genetics
Cyanobacteria - growth & development
Cyanobacteria - physiology
Darkness
Ecology, environment
Flow Cytometry
Gene Dosage
Gene Expression Regulation, Bacterial
Genes, Bacterial
Genes, Bacterial - genetics
Life Sciences
Light
Operon
Operon - genetics
Photosynthesis
Photosynthesis - genetics
Promoter Regions, Genetic
Promoter Regions, Genetic - genetics
RNA, Bacterial
RNA, Bacterial - analysis
RNA, Bacterial - genetics
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Summary:The continuous changes in incident solar light occurring during the day oblige oxyphototrophs, such as the marine prokaryote Prochlorococcus, to modulate the synthesis and degradation rates of their photosynthetic components finely. How this natural phenomenon influences the diel expression of photosynthetic genes has never been studied in this ecologically important oxyphotobacterium. Here, the high light‐adapted strain Prochlorococcus sp. PCC 9511 was grown in large‐volume continuous culture under a modulated 12 h−12 h light–dark cycle mimicking the conditions found in the upper layer of equatorial oceans. The pcbA gene encoding the major light‐harvesting complex showed strong diel variations in transcript levels with two maxima, one before the onset of illumination and the other near the end of the photoperiod. In contrast, the mRNA level of psbA (encoding the reaction centre II subunit D1), the monocistronic transcript of psbD (encoding D2) and the dicistronic transcript of psbDC were all tightly correlated with light irradiance, with a minimum at night and a maximum at noon. The occurrence of a second peak during the dark period for the monocistronic transcript of psbC (encoding one of the PS II core Chl a antenna proteins) suggested the involvement of post‐transcriptional regulation. Differential expression of the external antenna and core genes may constitute a mechanism of regulation of the antenna size to cope with the excess photon fluxes that Prochlorococcus cells experience in the upper layer of oceans around midday. The 5′ ends of all transcripts were mapped, and a conserved motif, 5′‐TTGATGA‐3′, was identified within the putative psbA and pcbA promoters.
ISSN:1462-2912
1462-2920
DOI:10.1046/j.1462-2920.2001.00173.x