title: Stoichiometry of the photosynthetic apparatus and phycobilisome structure of the cyanobacterium Plectonema boryanum UTEX 485 are regulated by both light and temperature.
abstract: The role of growth temperature and growth irradiance on the regulation of the stoichiometry and function of the photosynthetic apparatus was examined in the cyanobacterium Plectonema boryanum UTEX 485 by comparing mid-log phase cultures grown at either 29 degrees C/150 micromol m(-2) s(-1), 29 degrees C/750 micromol m(-2) s(-1), 15 degrees C/150 micromol m(-2) s(-1), or 15 degrees C/10 micromol m(-2) s(-1). Cultures grown at 29 degrees C/750 micromol m(-2) s(-1) were structurally and functionally similar to those grown at 15 degrees C/150 micromol m(-2) s(-1), whereas cultures grown at 29 degrees C/150 micromol m(-2) s(-1) were structurally and functionally similar to those grown at 15 degrees C/10 micromol m(-2) s(-1). The stoichiometry of specific components of the photosynthetic apparatus, such as the ratio of photosystem (PS) I to PSII, phycobilisome size and the relative abundance of the cytochrome b(6)/f complex, the plastoquinone pool size, and the NAD(P)H dehydrogenase complex were regulated by both growth temperature and growth irradiance in a similar manner. This indicates that temperature and irradiance may share a common sensing/signaling pathway to regulate the stoichiometry and function of the photosynthetic apparatus in P. boryanum. In contrast, the accumulation of neither the D1 polypeptide of PSII, the large subunit of Rubisco, nor the CF(1) alpha-subunit appeared to be regulated by the same mechanism. Measurements of P700 photooxidation in vivo in the presence and absence of inhibitors of photosynthetic electron transport coupled with immunoblots of the NAD(P)H dehydrogenase complex in cells grown at either 29 degrees C/750 micromol m(-2) s(-1) or 15 degrees C/150 micromol m(-2) s(-1) are consistent with an increased flow of respiratory electrons into the photosynthetic intersystem electron transport chain maintaining P700 in a reduced state relative to cells grown at either 29 degrees C/150 micromol m(-2) s(-1) or 15 degrees C/10 micromol m(-2) s(-1). These results are discussed in terms of acclimation to excitation pressure imposed by either low growth temperature or high growth irradiance.
authors.affiliation: Department of Biology, University of Western Ontario, London, Ontario, Canada N6A 5B7.
authors.forename: Ewa
authors.initials: E
authors.lastname: Miskiewicz
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Ivanov
authors.forename: Norman P A
authors.initials: NP
authors.lastname: Huner
mesh_terms: D000064:Acclimatization / Q000502:physiology / Q000528:radiation effects; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism / Q000528:radiation effects; D002734:Chlorophyll / Q000037:antagonists & inhibitors / Q000378:metabolism; D000458:Cyanobacteria / Q000502:physiology* / Q000528:radiation effects; D003573:Cytochrome b Group / Q000187:drug effects / Q000378:metabolism; D045346:Cytochrome b6f Complex; D003580:Cytochromes / Q000187:drug effects / Q000378:metabolism; D045348:Cytochromes f; D004579:Electron Transport / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008027:Light; D045342:Light-Harvesting Protein Complexes; D009252:NADPH Dehydrogenase / Q000187:drug effects / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry / Q000378:metabolism* / Q000528:radiation effects; D045524:Phycobilisomes; D010971:Plastoquinone / Q000037:antagonists & inhibitors / Q000378:metabolism; D011506:Proteins / Q000737:chemistry / Q000378:metabolism* / Q000528:radiation effects; D015398:Signal Transduction / Q000187:drug effects / Q000528:radiation effects; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D003573:Cytochrome b Group; D003580:Cytochromes; D004791:Enzyme Inhibitors; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045524:Phycobilisomes; D011506:Proteins; D002734:Chlorophyll; C001785:chlorophyll P 700; D045346:Cytochrome b6f Complex; D045348:Cytochromes f; D009252:NADPH Dehydrogenase; D010971:Plastoquinone