title: Multiplication of antenna genes as a major adaptation to low light in a marine prokaryote.
abstract: Two ecotypes of the prokaryote Prochlorococcus adapted to distinct light niches in the ocean have been described recently. These ecotypes are characterized by their different (divinyl-) chlorophyll (Chl) a to Chl b ratios and 16S rRNA gene signatures, as well as by their significantly distinct irradiance optima for growth and photosynthesis [Moore, L. R., Rocap, G. & Chisholm, S. W. (1998) Nature (London) 393, 464-467]. However, the molecular basis of their physiological differences remained, so far, unexplained. In this paper, we show that the low-light-adapted Prochlorococcus strain SS120 possesses a gene family of seven transcribed genes encoding different Chl a/b-binding proteins (Pcbs). In contrast, Prochlorococcus sp. MED4, a high-light-adapted ecotype, possesses a single pcb gene. The presence of multiple antenna genes in another low-light ecotype (NATL2a), but not in another high-light ecotype (TAK9803-2), is demonstrated. Thus, the multiplication of pcb genes appears as a key factor in the capacity of deep Prochlorococcus populations to survive at extremely low photon fluxes.
authors.affiliation: Observatoire Océanologique de Roscoff, Centre National de la Recherche Scientifique et Université Paris 6, Station Biologique, B. P. 74, F-29682 Roscoff Cedex, France.
authors.forename: L
authors.initials: L
authors.lastname: Garczarek
authors.forename: W R
authors.initials: WR
authors.lastname: Hess
authors.forename: J
authors.initials: J
authors.lastname: Holtzendorff
authors.forename: G W
authors.initials: GW
authors.lastname: van der Staay
authors.forename: F
authors.initials: F
authors.lastname: Partensky
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D000458:Cyanobacteria / Q000235:genetics* / Q000502:physiology; D017931:DNA Primers; D005798:Genes, Bacterial; D008027:Light; D045342:Light-Harvesting Protein Complexes; D008969:Molecular Sequence Data; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry / Q000235:genetics*; D017386:Sequence Homology, Amino Acid
chemical_list: D017931:DNA Primers; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins