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Photosynthesis Research

Fatemeh Azadi-Chegeni, Christo Schiphorst, Anjali Pandit
We report the application of NMR dynamic spectral editing for probing the structure and dynamics of molecular constituents in fresh, intact cells and in freshly prepared thylakoid membranes of Chlamydomonas reinhardtii (Cr.) green algae. For isotope labeling, wild-type Cr. cells were grown on (13)C acetate-enriched minimal medium. 1D (13)C J-coupling based and dipolar-based MAS NMR spectra were applied to distinguish (13)C resonances of different molecular components. 1D spectra were recorded over a physiological temperature range, and whole-cell spectra were compared to those taken from thylakoid membranes, evaluating their composition and dynamics...
June 23, 2017: Photosynthesis Research
Misato Teramura, Jiro Harada, Hitoshi Tamiaki
A chlorosome is a large and efficient light-harvesting antenna system found in some photosynthetic bacteria. This system comprises self-aggregates of bacteriochlorophyll (BChl) c, d, or e possessing a chiral 1-hydroxyethyl group at the 3-position, which plays a key role in the formation of the supramolecule. Biosynthesis of chlorosomal pigments involves stereoselective conversion of 3-vinyl group to 3-(1-hydroxyethyl) group facilitated by a 3-vinyl hydratase. This 3-vinyl hydration also occurs in BChl a biosynthesis, followed by oxidation that introduces an acetyl group at the 3-position...
June 22, 2017: Photosynthesis Research
Ayaka Wada, Hitoshi Tamiaki
Zinc 3-hydroxymethyl-13(1)-oxo-chlorins bearing a variety of primary alkyl groups at the 20-position were prepared as models of bacteriochlorophyll-c by chemical modification of naturally occurring chlorophyll-a. The synthetic chlorophyll-a derivatives self-aggregated in an aqueous Triton X-100 solution to afford large oligomers whose Soret and Qy bands were red-shifted and broadened, compared with the bands of their monomers in tetrahydrofuran. The oligomeric bands are similar to those of bacteriochlorophyll-c self-aggregates in chlorosomes, the main light-harvesting antennae of photosynthetic green bacteria...
June 22, 2017: Photosynthesis Research
Sen Rao, Yanyou Wu
Water deficit is one of the key factors that limits the carbon (C) assimilation and productivity of plants. The effect of variable water deficit on recently root-derived bicarbonate assimilation in Camptotheca acuminate seedlings was investigated. Three-month-old seedlings were subjected to three water regimes, well-watered (WW), moderate stress (MS), and severe stress (SS) induced by polyethyleneglycol, in conjunction with relatively high (H) and low (L) natural (13)C-abundance of NaHCO3-labeled treatments in hydroponics for 14 days...
June 16, 2017: Photosynthesis Research
Anne Sawyer, Martin Winkler
Ferredoxins are soluble iron sulphur proteins which function as electron donors in a number of metabolic pathways in a broad range of organisms. In photosynthetic organisms, PETF, or ferredoxin 1 (FDX1), is the most studied ferredoxin due to its essential role in photosynthesis, where it transfers electrons from photosystem I to ferredoxin-NADP(+) oxidoreductase. However, PETF can also transfer electrons to a large number of other proteins. One important PETF electron acceptor found in green microalgae is the biologically and biotechnologically important [FeFe]-hydrogenase HYDA, which catalyses the production of molecular hydrogen (H2) from protons and electrons...
June 15, 2017: Photosynthesis Research
Laura Mosebach, Claudia Heilmann, Risa Mutoh, Philipp Gäbelein, Janina Steinbeck, Thomas Happe, Takahisa Ikegami, Guy Hanke, Genji Kurisu, Michael Hippler
Ferredoxins (FDX) and the FDX:NADP(+) oxidoreductase (FNR) represent a key junction of electron transport downstream of photosystem I (PSI). Dynamic recruitment of FNR to the thylakoid membrane has been considered as a potential mechanism to define the fate of photosynthetically derived electrons. In this study, we investigated the functional importance of the association of FNR with the photosynthetic apparatus in Chlamydomonas reinhardtii. In vitro assays based on NADP(+) photoreduction measurements as well as NMR chemical shift perturbation analyses showed that FNR preferentially interacts with FDX1 compared to FDX2...
June 7, 2017: Photosynthesis Research
Ido Eisenberg, Dvir Harris, Yael Levi-Kalisman, Shira Yochelis, Asaf Shemesh, Gili Ben-Nissan, Michal Sharon, Uri Raviv, Noam Adir, Nir Keren, Yossi Paltiel
Cyanobacteria light-harvesting complexes can change their structure to cope with fluctuating environmental conditions. Studying in vivo structural changes is difficult owing to complexities imposed by the cellular environment. Mimicking this system in vitro is challenging, as well. The in vivo system is highly concentrated, and handling similar in vitro concentrated samples optically is difficult because of high absorption. In this research, we mapped the cyanobacteria antennas self-assembly pathways using highly concentrated solutions of phycocyanin (PC) that mimic the in vivo condition...
June 2, 2017: Photosynthesis Research
June Southall, Sarah L Henry, Alastair T Gardiner, Aleksander W Roszak, William Mullen, Anne-Marie Carey, Sharon M Kelly, Claire Ortmann de Percin Northumberland, Richard J Cogdell
Rhodopseudomonas palustris is a species of purple photosynthetic bacteria that has a multigene family of puc genes that encode the alpha and beta apoproteins, which form the LH2 complexes. A genetic dissection strategy has been adopted in order to try and understand which spectroscopic form of LH2 these different genes produce. This paper presents a characterisation of one of the deletion mutants generated in this program, the pucBAd only mutant. This mutant produces an unusual spectroscopic form of LH2 that only has a single large NIR absorption band at 800 nm...
May 31, 2017: Photosynthesis Research
Jörg Pieper, Margus Rätsep, Maksym Golub, Franz-Josef Schmitt, Petrica Artene, Hann-Jörg Eckert
The cyanobacterium Acaryochloris marina developed two types of antenna complexes, which contain chlorophyll-d (Chl d) and phycocyanobilin (PCB) as light-harvesting pigment molecules, respectively. The latter membrane-extrinsic complexes are denoted as phycobiliproteins (PBPs). Spectral hole burning was employed to study excitation energy transfer and electron-phonon coupling in PBPs. The data reveal a rich spectral substructure with a total of four low-energy electronic states whose absorption bands peak at 633, 644, 654, and at about 673 nm...
May 31, 2017: Photosynthesis Research
Tomas E van den Berg, Bart van Oort, Roberta Croce
The colonial green alga Botryococcus braunii (BB) is a potential source of biofuel due to its natural high hydrocarbon content. Unfortunately, its slow growth limits its biotechnological potential. Understanding its photosynthetic machinery could help to identify possible growth limitations. Here, we present the first study on BB light-harvesting complexes (LHCs). We purified two LHC fractions containing the complexes in monomeric and trimeric form. Both fractions contained at least two proteins with molecular weight (MW) around 25 kDa...
May 27, 2017: Photosynthesis Research
Benjamin M Wolf, Dariusz M Niedzwiedzki, Nikki Cecil M Magdaong, Robyn Roth, Ursula Goodenough, Robert E Blankenship
Oxygenic phototrophs typically utilize visible light (400-700 nm) to drive photosynthesis. However, a large fraction of the energy in sunlight is contained in the far-red region, which encompasses light beyond 700 nm. In nature, certain niche environments contain high levels of this far-red light due to filtering by other phototrophs, and in these environments, organisms with photosynthetic antenna systems adapted to absorbing far-red light are able to thrive. We used selective far-red light conditions to isolate such organisms in environmental samples...
May 25, 2017: Photosynthesis Research
Thomas Kieselbach, Otilia Cheregi, Beverley R Green, Christiane Funk
Plants and algae have developed various light-harvesting mechanisms for optimal delivery of excitation energy to the photosystems. Cryptophyte algae have evolved a novel soluble light-harvesting antenna utilizing phycobilin pigments to complement the membrane-intrinsic Chl a/c-binding LHC antenna. This new antenna consists of the plastid-encoded β-subunit, a relic of the ancestral phycobilisome, and a novel nuclear-encoded α-subunit unique to cryptophytes. Together, these proteins form the active α1β·α2β-tetramer...
May 24, 2017: Photosynthesis Research
Chang Sun
Bacterial reaction centers (RC) from Rhodobacter sphaeroides have been widely used to functionalize electrodes and to generate photocurrent. However, in most studies, direct electron transfer from the semiquinone to the electrode was not observed because the H subunit of the RC shields the semiquinone. It is demonstrated in the current work that removal of the H subunit effectively exposes the semiquinone sites in the LM dimer. This is demonstrated by measuring the second-order rate constant for the reaction between ferricyanide and the anionic semiquinone Q A(-) formed by an actinic flash...
May 24, 2017: Photosynthesis Research
Wenxing He, Shunsuke Adachi, Rowan F Sage, Taiichiro Ookawa, Tadashi Hirasawa
The high-yielding indica rice variety, 'Takanari', has the high rate of leaf photosynthesis compared with the commercial japonica varieties. Among backcrossed inbred lines from a cross between 'Takanari' and a japonica variety, 'Koshihikari', two lines, BTK-a and BTK-b, showed approximately 20% higher photosynthetic rate than that of 'Takanari' for a flag leaf at full heading. This is a highest recorded rate of rice leaf photosynthesis. Here, the timing and cause of the increased leaf photosynthesis in the BTK lines were investigated by examining the photosynthesis and related parameters, as well as mesophyll cell anatomy during ontogenesis...
May 24, 2017: Photosynthesis Research
Rina Honoki, Sumire Ono, Akira Oikawa, Kazuki Saito, Shinji Masuda
The regulatory nucleotides, guanosine 5'-triphosphate 3'-diphosphate (pppGpp) and guanosine 5'-diphosphate 3'-diphosphate (ppGpp), were originally identified in Escherichia coli, and control a large set of gene expression and enzyme activities. The (p)ppGpp-dependent control of cell activities is referred to as the stringent response. A growing number of (p)ppGpp synthase/hydrolase homologs have been identified in plants, which are localized in plastids in Arabidopsis thaliana. We recently reported that the Arabidopsis mutant overproducing ppGpp in plastids showed dwarf chloroplasts, and transcript levels in the mutant plastids were significantly suppressed...
May 23, 2017: Photosynthesis Research
Margaret Gwyn Latimer, Thomas T Bannister, Govindjee
We provide here a brief tribute to Paul Henry Latimer (November 25, 1925 to October 1, 2011), a dedicated biological physicist, discoverer of selective scattering in biological systems, a wonderful teacher, husband, and father. We provide here a glimpse of his personal and professional life, including reminiscences from F. Dudley Bryant, Dan A. Cross, Bobby E. Pyle, Bryan L. Seiber, and Bruce A. Seiber.
May 23, 2017: Photosynthesis Research
Václav Šlouf, Gürkan Keşan, Radek Litvín, David J K Swainsbury, Elizabeth C Martin, C Neil Hunter, Tomáš Polívka
RC-LH1-PufX complexes from a genetically modified strain of Rhodobacter sphaeroides that accumulates carotenoids with very long conjugation were studied by ultrafast transient absorption spectroscopy. The complexes predominantly bind the carotenoid diketospirilloxanthin, constituting about 75% of the total carotenoids, which has 13 conjugated C=C bonds, and the conjugation is further extended to two terminal keto groups. Excitation of diketospirilloxanthin in the RC-LH1-PufX complex demonstrates fully functional energy transfer from diketospirilloxanthin to BChl a in the LH1 antenna...
May 20, 2017: Photosynthesis Research
Erling Thyrhaug, Craig N Lincoln, Federico Branchi, Giulio Cerullo, Václav Perlík, František Šanda, Heiko Lokstein, Jürgen Hauer
The peripheral light-harvesting antenna complex (LH2) of purple photosynthetic bacteria is an ideal testing ground for models of structure-function relationships due to its well-determined molecular structure and ultrafast energy deactivation. It has been the target for numerous studies in both theory and ultrafast spectroscopy; nevertheless, certain aspects of the convoluted relaxation network of LH2 lack a satisfactory explanation by conventional theories. For example, the initial carotenoid-to-bacteriochlorophyll energy transfer step necessary on visible light excitation was long considered to follow the Förster mechanism, even though transfer times as short as 40 femtoseconds (fs) have been observed...
May 18, 2017: Photosynthesis Research
Govindjee, John C Munday, George C Papageorgiou
We present here a Tribute to Frederick Yi-Tung Cho (1939-2011), an innovative and ingenious biophysicist and an entrepreneur. He was one of the 4 earliest PhD students [see: Cederstrand (1965)-Carl Nelson Cederstrand; coadvisor: Eugene Rabinowitch; Papageorgiou (1968)-George C. Papageorgiou (coauthor of this paper); and Munday (1968)-John C. Munday Jr. (also a coauthor of this paper)] of one of us (Govindjee) in Biophysics at the University of Illinois at Urbana-Champaign (UIUC) during the late 1960s (1963-1968)...
May 18, 2017: Photosynthesis Research
Alexander N Tikhonov, Alexey V Vershubskii
No abstract text is available yet for this article.
May 18, 2017: Photosynthesis Research
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