Characterization of a light-responding trans-activator responsible for differentially controlling reaction center and light-harvesting-I gene expression in Rhodobacter capsulatus.
The purple nonsulfur photosynthetic bacterium Rhodobacter capsulatus regulates synthesis of its photosystem in response to two environmental stimuli, oxygen tension and light intensity. Here we describe the identification and characterization of the trans-acting regulatory gene hvrA, which we show is involved in differentially controlling reaction center and light-harvesting gene expression in response to alterations in light intensity. An hvrA mutant strain is shown to lack the capability to trans-activate light-harvesting-I and reaction center gene expression but retain normal light-harvesting-II and photopigment regulation, in response to a reduction in light intensity. As a consequence of altered expression, hvrA mutant strains exhibit reduced photosynthetic growth capabilities under dim-light conditions. The results of this study and additional studies indicate that regulated synthesis of the photosystem involves complex sets of overlapping regulatory circuits that differentially control photosystem gene expression in response to environmental stimuli such as oxygen tension and light intensity.
Department of Biology, Indiana University, Bloomington 47405.
J J
JJ
Buggy
M W
MW
Sganga
C E
CE
Bauer
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D015152:Blotting, Northern; D004252:DNA Mutational Analysis; D004307:Dose-Response Relationship, Radiation; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects / Q000528:radiation effects*; D008027:Light; D045342:Light-Harvesting Protein Complexes; D008969:Molecular Sequence Data; D010100:Oxygen / Q000494:pharmacology; D045322:Photosynthetic Reaction Center Complex Proteins / Q000096:biosynthesis / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D016354:Rhodobacter capsulatus / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development / Q000528:radiation effects; D017422:Sequence Analysis, DNA; D013053:Spectrophotometry; D015534:Trans-Activators / Q000235:genetics*; D014158:Transcription, Genetic
D001426:Bacterial Proteins; C090405:HvrA protein, Rhodobacter capsulatus; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; C094744:light-harvesting complex 1, Rhodospirillum; D010100:Oxygen