Isolation and characterization of light-regulated phycobilisome linker polypeptide genes and their transcription as a polycistronic mRNA

Abstract

Several cyanobacteria adjust both the phycobiliprotein and linker protein composition of the phycobilisome, a light-harvesting complex in cyanobacteria and some eucaryotic algae, to maximize absorption of prevalent wavelengths of light. This process is called complementary chromatic adaptation. We sequenced the amino terminus of a linker polypeptide which is associated with phycocyanin and accumulates to high levels during growth of the cyanobacterium Fremyella diplosiphon in red light. A mixed oligonucleotide encoding a region of this amino terminus was synthesized and used to identify a fragment of F. diplosiphon genomic DNA encoding the linker polypeptide. This linker gene was located between two other linker genes and contiguous to the red-light-induced phycocyanin gene set. Sequences of all three linker genes are presented. These genes were transcribed together onto a large polycistronic mRNA which also encoded the red-light-induced phycocyanin subunits. The relationship of this transcript to the biogenesis of the phycobilisome when F. diplosiphon is grown under different conditions of illumination is discussed.

Characterization of the light-regulated operon encoding the phycoerythrin-associated linker proteins from the cyanobacterium Fremyella diplosiphon

“…1). Differences in both the phycobiliproteins and the linker proteins are evident in phycobilisome preparations isolated from different light regimens as previously described (9,32). The phycoerythrin-associated linker proteins (CpeC and CpeD) are present at high levels in green light ( Fig.…”

“…The cpcl operon encodes the ,B and a subunits of a phycocyanin which is expressed at similar levels in green and red light (constitutive phycocyanin) (14). The cpc2 operon encodes phycocyanin subunits and associated linker proteins that are expressed in red, but not in green, light (inducible phycocyanin) (14,32). In phycobilisomes from cells grown in both red and green light, the constitutive phycocyanin probably occupies the portion of the rods proximal to the core; the rod substructure is completed in red light-grown cells by the inducible phycocyanin hexamers with associated linker proteins.…”

Characterization and Expression of Two cDNAs Encoding Carbonic Anhydrase in Arabidopsis thaliana

“…Filters were prehybridized in hybridization ovens for 1 h in 0.5 M NaCl, 0.1 M NaH2P04, 0.1 M Tris, 2 m EDTA, 0.1% SDS and hybridized ovemight in fresh solution plus the labeled probe. This was followed by three washes at room temperature for 15 min in 10 m NaP04 (pH 6.5), 2 EDTA, 0.1% SDS and one wash for 45 min in 50 ~TLM NaP04 (pH 6.5), 2 mM EDTA, 0.1% SDS (Lomax et al, 1987). The temperatures of hybridization and the final wash varied in the different screening strategies.…”

A molecular understanding of complementary chromatic adaptation

“…Since there is little change in the half-lives of mRNAs encoding the phycobiliproteins in RL and GL (Oelmüller et al 1988a), levels of PE and PC i appear to be primarily regulated by changes in rates of transcription of the cpeBA and cpcB2A2 operons, respectively. Furthermore, genes encoding the linker polypeptides associated with PC i , cpcHID, are RL-inducible and co-transcribed with cpcB2A2 (Lomax et al 1987). And while genes encoding the linker polypeptides associated with PE, cpeCDE, are also under the control of RL and GL, they are not in the same operon as cpeBA (Federspiel and Grossman 1990;Federspiel and Scott 1992).…”