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Multiplication of antenna genes as a major adaptation to low light in a marine prokaryote

2000; National Academy of Sciences; Volume: 97; Issue: 8 Linguagem: Inglês

10.1073/pnas.070040897

1091-6490

Laurence Garczarek, Wolfgang R. Hess, Julia Holtzendorff, Georg W.M. van der Staay, Frédéric Partensky,

Genomics and Phylogenetic Studies

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.