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°C/150 mol m Ϫ2 . 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 ␣-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°C/750 mol m Ϫ2 s Ϫ1 or 15°C/150 mol m Ϫ2 s Ϫ1 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°C/150 mol m Ϫ2 s Ϫ1 or 15°C/10 mol m Ϫ2 s Ϫ1 . These results are discussed in terms of acclimation to excitation pressure imposed by either low growth temperature or high growth irradiance.Cyanobacteria are a large and diverse group of prokaryotes performing oxygenic photosynthesis in a manner similar to green algae and plants. The cyanobacterial photosynthetic apparatus consists of five multiprotein complexes. PSII, cytochrome b 6 f, PSI, and ATP synthase are common to both cyanobacteria and plants. However, the fifth complex, a lightharvesting antenna of PSII, is functionally but not structurally homologous (Gantt, 1994). In cyanobacteria, light harvesting is mediated by phycobilisomes (PBSs), complex protein structures located on the cytoplasmic surface of the thylakoid membranes. The major components of the PBS are the biliproteins, allophycocyanin (AP), phycocyanin (PC), phycoerythrin, and phycoerythrocyanin, with covalently attached bilin chromophores. Different colorless linker polypeptides are specifically associated with each type of phycobiliprotein and function to stabilize the PBS and optimize their absorbance and energy transfer characteristics. The PBSs are composed of two structural domains: an AP core that is in direct contact with the thylakoid membrane and generally six rods of stacked PC and, in some strains, phycoerythrin or phycoerythrocyanin hexamers radiating from the core (Sidler, 1994).Another important distinction between cyanobacteria and chloroplasts is that in cyanobacteria, both respiratory and photosynthetic electron transport chains function within thylakoid membranes, wh...

Long-Term Acclimation of the Cyanobacterium Synechocystis sp. PCC 6803 to High Light Is Accompanied by an Enhanced Production of Chlorophyll That Is Preferentially Channeled to Trimeric Photosystem I

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Physiological constraints on the global distribution of <i>Trichodesmium</i> – effect of temperature on diazotrophy

“…Photosynthetic organisms will acclimate to both light and temperature by adjusting the balance between light energy absorption and the rate of the dark reaction of photosynthesis, i.e. by increasing light absorption in low light and decreasing it at low temperature (Geider et al, 1997;Miskiewicz et al, 2002). The photosynthetic quantum yield efficiency clearly reflects a physiological adaptation to the temperature tolerance range of Trichodesmium (IMS-101).…”

Photosynthetic Redox Imbalance Governs Leaf Sectoring in theArabidopsis thalianaVariegation Mutantsimmutans,spotty,var1, andvar2

“…nitrogen deficiency (Cruz et al, 2003), and salt stress (Huang et al, 2005) increase excitation pressure due to energy imbalances between photochemistry and cellular energy use ( Figure 1). In the single-cell green algae, C. vulgaris, Dunaliella salina, and D. tertiolecta (Escoubas et al, 1995;Maxwell et al, 1995aMaxwell et al, , 1995b as well as the cyanobacterium Plectonema boryanum (Miskiewicz et al, 2000(Miskiewicz et al, , 2002, this typically results in a high excitation pressure phenotype characterized by a decrease in chlorophyll per cell, a decreased abundance of pigments associated with the light-harvesting antenna, and a decreased photosynthetic efficiency typically associated with photoacclimation. These algae and P. boryanum adjust the structure and composition of light-harvesting complex II and phycobilisomes, respectively, reflecting their acclimation response to high excitation pressure.…”