title: Low-light-adapted Prochlorococcus species possess specific antennae for each photosystem.
abstract: Prochlorococcus, the most abundant genus of photosynthetic organisms, owes its remarkably large depth distribution in the oceans to the occurrence of distinct genotypes adapted to either low- or high-light niches. The pcb genes, encoding the major chlorophyll-binding, light-harvesting antenna proteins in this genus, are present in multiple copies in low-light strains but as a single copy in high-light strains. The basis of this differentiation, however, has remained obscure. Here we show that the moderate low-light-adapted strain Prochlorococcus sp. MIT 9313 has one iron-stress-induced pcb gene encoding an antenna protein serving photosystem I (PSI)--comparable to isiA genes from cyanobacteria--and a constitutively expressed pcb gene encoding a photosystem II (PSII) antenna protein. By comparison, the very low-light-adapted strain SS120 has seven pcb genes encoding constitutive PSI and PSII antennae, plus one PSI iron-regulated pcb gene, whereas the high-light-adapted strain MED4 has only a constitutive PSII antenna. Thus, it seems that the adaptation of Prochlorococcus to low light environments has triggered a multiplication and specialization of Pcb proteins comparable to that found for Cab proteins in plants and green algae.
authors.affiliation: Wolfson Laboratories, Biochemistry Building, Department of Biological Sciences, South Kensington Campus, Imperial College London, London SW7 2AZ, UK.
authors.forename: T S
authors.initials: TS
authors.lastname: Bibby
authors.forename: I
authors.initials: I
authors.lastname: Mary
authors.forename: J
authors.initials: J
authors.lastname: Nield
authors.forename: F
authors.initials: F
authors.lastname: Partensky
authors.forename: J
authors.initials: J
authors.lastname: Barber
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics / Q000528:radiation effects*; D001426:Bacterial Proteins / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics; D000458:Cyanobacteria / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects* / Q000648:ultrastructure; D004777:Environment; D018628:Gene Dosage; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial / Q000235:genetics*; D005838:Genotype; D008027:Light; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics* / Q000528:radiation effects
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; C076726:chlorophyll A binding protein CP43, Cyanobacteria