The long-term objectives of this research program are to develop a detailed understanding of the structure, function, biogenesis, and regulation of the cyanobacterial photosynthetic apparatus. The dual goals of providing a detailed understanding of how light-harvesting anennae function as well as providing molecular tools which are especially important in characterizing gene regulation responses of cyanobacteria to nutrients and light intensity are being pursued. The RNA polymerase of Synechococcus sp. PCC 7002 apparently employs several different sigma factors. The hypothesis that global patterns of gene expression in cyanobacteria are controlled by promoter selection by these multiple sigma factors will be tested. Sigma factor proteins will be overproduced in E. coli and reconstituted with core RNA polymerase for in vitro transcription studies. The long-term aim is to correlate sigma factors with specific promoter sequences and with patterns of gene expression. All oxygen- evolving photosynthetic organisms exhibit an adaptive phenomenon called """"""""state transitions"""""""" by which light energy is distributed between the two photosystems to maximize the overall rate of photosynthetic election transport. The ApcD gene product is required for state transitions to occur and for energy to be transferred to Photosystem I. The hypothesis that post-translational modification of ApcD controls light energy distribution within the phycobilisome will be tested. Additional experiments will seek to demonstrate the contact partner of ApcD on the Photosystem I reaction center. Strains, plasmids, and methods to create site-specifically altered phycocyanins have been generated. These tools will now be used to address specific aspects of structure and function for phycocyanin through site-directed mutagenesis. Spectroscopic analyses of the mutant phycocyanins will be performed, and proteins exhibiting interesting defects in light-energy harvesting will be studied in collaboration with Dr. Robert Huber by X-ray crystallography. The ApcE protein plays critical roles in energy transfer to Photosystem II as well as in directing core assembly in the phycobilisome. Additional structure and function studies will be performed on this interesting protein, and the hypothesis that phycobilisome core structure is intrinsically determined by the number of linker domains in ApcE will be tested. The proposal that phycobilisomes of Anabaena sp. PCC 7120 contain four classes of peripheral rods and a total of eight rods attached to their cores will also be tested. The location of ferredoxin NADP+ oxidoreductase in phycobilisomes will be studied by immuno-electron microscopy, and the role of this molecule in phycobilisomes will studied by construction of a mutant lacking the recently identified CpcD-like domain. Finally, a bank of interposon- or transposon-tagged mutants will be created which will be screened for mutations affecting phycocyanobilin synthesis, covalent attachment of phycocyanobilin to phycobiliproteins, and state transitions. The successful completion of this program should significantly extend knowledge of mechanisms regulating gene expression in the photoautotrophic cyanobacteria and will additionally provide significant new insights into how light energy is efficiently harvested and distributed to the photosystems.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
Project #
Application #
Study Section
Bacteriology and Mycology Subcommittee 2 (BM)
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Pennsylvania State University
Schools of Arts and Sciences
University Park
United States
Zip Code
Shen, Gaozhong; Schluchter, Wendy M; Bryant, Donald A (2008) Biogenesis of phycobiliproteins: I. cpcS-I and cpcU mutants of the cyanobacterium Synechococcus sp. PCC 7002 define a heterodimeric phyococyanobilin lyase specific for beta-phycocyanin and allophycocyanin subunits. J Biol Chem 283:7503-12
Saunee, Nicolle A; Williams, Shervonda R; Bryant, Donald A et al. (2008) Biogenesis of phycobiliproteins: II. CpcS-I and CpcU comprise the heterodimeric bilin lyase that attaches phycocyanobilin to CYS-82 OF beta-phycocyanin and CYS-81 of allophycocyanin subunits in Synechococcus sp. PCC 7002. J Biol Chem 283:7513-22
Woodger, Fiona J; Bryant, Donald A; Price, G Dean (2007) Transcriptional regulation of the CO2-concentrating mechanism in a euryhaline, coastal marine cyanobacterium, Synechococcus sp. Strain PCC 7002: role of NdhR/CcmR. J Bacteriol 189:3335-47
Inoue-Sakamoto, Kaori; Gruber, Tanja M; Christensen, Suzanne K et al. (2007) Group 3 sigma factors in the marine cyanobacterium Synechococcus sp. strain PCC 7002 are required for growth at low temperature. J Gen Appl Microbiol 53:89-104
Shen, Gaozhong; Saunee, Nicolle A; Williams, Shervonda R et al. (2006) Identification and characterization of a new class of bilin lyase: the cpcT gene encodes a bilin lyase responsible for attachment of phycocyanobilin to Cys-153 on the beta-subunit of phycocyanin in Synechococcus sp. PCC 7002. J Biol Chem 281:17768-78
Frigaard, Niels-Ulrik; Sakuragi, Yumiko; Bryant, Donald A (2004) Gene inactivation in the cyanobacterium Synechococcus sp. PCC 7002 and the green sulfur bacterium Chlorobium tepidum using in vitro-made DNA constructs and natural transformation. Methods Mol Biol 274:325-40
Wang, Tao; Shen, Gaozhong; Balasubramanian, Ramakrishnan et al. (2004) The sufR gene (sll0088 in Synechocystis sp. strain PCC 6803) functions as a repressor of the sufBCDS operon in iron-sulfur cluster biogenesis in cyanobacteria. J Bacteriol 186:956-67
Yu, Jianping; Shen, Gaozhong; Wang, Tao et al. (2003) Suppressor mutations in the study of photosystem I biogenesis: sll0088 is a previously unidentified gene involved in reaction center accumulation in Synechocystis sp. strain PCC 6803. J Bacteriol 185:3878-87
Gomez-Lojero, Carlos; Perez-Gomez, Bertha; Shen, Gaozhong et al. (2003) Interaction of ferredoxin:NADP+ oxidoreductase with phycobilisomes and phycobilisome substructures of the cyanobacterium Synechococcus sp. strain PCC 7002. Biochemistry 42:13800-11
Huang, Chenhui; Yuan, Xiaolin; Zhao, Jindong et al. (2003) Kinetic analyses of state transitions of the cyanobacterium Synechococcus sp. PCC 7002 and its mutant strains impaired in electron transport. Biochim Biophys Acta 1607:121-30

Showing the most recent 10 out of 50 publications