Phycobilisomes are major light harvesting complexes in cyanobacteria and some eukaryotic algae. The complex includes both pigmented proteins (phycobiliproteins) and nonpigmented proteins (linker proteins). The phycobiliproteins in eukaryotic algae are synthesized in the chloroplast while the nonpigmented linker proteins are synthesized in the cytoplasm (and must be imported into the organelle). Since the subunits among the different phycobiliproteins are related, they are thought to represent a gene family localized to the plastid DNA. Recently, a gene encoding the Beta subunit of phycocyanin has been placed on the small single copy region (this region encodes at least one additional phycobiliprotein subunit) of the plastid genome of Cyanophora paradoxa. We propose to locate the other phycobiliprotein subunits (Alpha phycocyanin and Alpha and Beta allophycocyanin) on the plastid genome, determine whether these genes are transcribed separately or as a unit, and generate specific probes for identifying analogous genes in cyanobacteria. The synthesis of several phycobiliprotein subunits in cyanobacteria is regulated by light (complementary chromatic adaptation), and this regulation may be at the transcriptional level. The probes generated from the plastid genome of C. paradoxa will enable us to identify these light-regulated phycobiliprotein genes and analyze the molecular events involved in complementary chromatic adaptation. Experiments involving differential hybridizations of RNA isolated from cyanobacteria grown in different light qualities to clone banks of cyanobacterial DNA, and immunological techniques which would enable us to identify clones synthesizing phycobilisome polypeptides, would also aid in the isolation of light-regulated phycobilisome genes. Once these genes are obtained, we will examine their arrangement on the cyanobacterial genome (clustered or dispersed), characterize their transcription (especially in response to different light qualities) and sequence their 5' ends to establish features which might be essential for light-regulated transcription.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
1R01GM033436-01A1
Application #
3283159
Study Section
Molecular Cytology Study Section (CTY)
Project Start
1984-12-01
Project End
1987-11-30
Budget Start
1984-12-01
Budget End
1985-11-30
Support Year
1
Fiscal Year
1985
Total Cost
Indirect Cost
Name
Carnegie Institution of Washington, D.C.
Department
Type
DUNS #
072641707
City
Washington
State
DC
Country
United States
Zip Code
20005
Casey, E S; Grossman, A (1994) In vivo and in vitro characterization of the light-regulated cpcB2A2 promoter of Fremyella diplosiphon. J Bacteriol 176:6362-74
Schaefer, M R; Chiang, G G; Cobley, J G et al. (1993) Plasmids from two morphologically distinct cyanobacterial strains share a novel replication origin. J Bacteriol 175:5701-5
Chiang, G G; Schaefer, M R; Grossman, A R (1992) Complementation of a red-light-indifferent cyanobacterial mutant. Proc Natl Acad Sci U S A 89:9415-9
Bruns, B U; Briggs, W R; Grossman, A R (1989) Molecular characterization of phycobilisome regulatory mutants of Fremyella diplosiphon. J Bacteriol 171:901-8
Conley, P B; Lemaux, P G; Grossman, A (1988) Molecular characterization and evolution of sequences encoding light-harvesting components in the chromatically adapting cyanobacterium Fremyella diplosiphon. J Mol Biol 199:447-65
Lomax, T L; Conley, P B; Schilling, J et al. (1987) Isolation and characterization of light-regulated phycobilisome linker polypeptide genes and their transcription as a polycistronic mRNA. J Bacteriol 169:2675-84
Grossman, A R; Lemaux, P G; Conley, P B (1986) Regulated synthesis of phycobilisome components. Photochem Photobiol 44:827-37
Conley, P B; Lemaux, P G; Lomax, T L et al. (1986) Genes encoding major light-harvesting polypeptides are clustered on the genome of the cyanobacterium Fremyella diplosiphon. Proc Natl Acad Sci U S A 83:3924-8
Lemaux, P G; Grossman, A R (1985) Major light-harvesting polypeptides encoded in polycistronic transcripts in a eukaryotic alga. EMBO J 4:1911-9
Conley, P B; Lemaux, P G; Grossman, A R (1985) Cyanobacterial light-harvesting complex subunits encoded in two red light-induced transcripts. Science 230:550-3