The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Anthony W. D. Larkum - One of the best experts on this subject based on the ideXlab platform.
-
sequence of prochloron didemni atpbe and the inference of chioroplast origins endosymbiosis prochlorophyta phylogeny atp synthase cyanobacteria
2016Co-Authors: Peter J Lockhart, T J Beanlandt, C J Howet, Anthony W. D. LarkumAbstract:The Prochlorophytes, oxygenic photosyn- thetic prokaryotes containing chlorophylls a and b, have been put forward as descended from the organisms that gave rise to chloroplasts of green planis and algae by endosymbiosis, although this has always been controversial. To assess the phylogenetic position of the prochlorophyte Prochloron di- demni, we have cloned and sequenced its atpBE genes. Phylo- genetic inference under a range of models gives moderate to strong support for a cyanobacterial grouping rather than a chloroplast one. Possible systematic errors in this and previous analyses of prochlorophyte sequences are discussed. 1. ~~~~~2. 3.
-
light harvesting chlorophyll c like pigment inprochloron endosymbiosis phylogeny prochlorophyta
2007Co-Authors: Anthony W. D. Larkum, C Scaramuzzi, G. C. Cox, R. G. HillertAbstract:Achlorophyll c-like pigment, similar tomag- nesium-3,8-divinyl pheoporphyrin asmonomethyl ester, has beenisolated fromProchloron sp.obtained fromfive species of didemnid ascidians fromtheGreatBarrier Reef, Australia, andfromPalau, Micronesia. Thepigment represents 4-15%of thetotal chlorophyll content andisshowntofunction ina light-harvesting pigment protein complex ofProchloron. The observation that all ofthemajor chlorophylls (a+b+c) function inalight-harvesting role inProchloron andpossibly inother Prochlorophytes isdiscussed intermsofthephylogeny ofthe Prochlorophytes.
-
structure of a photosystem ii supercomplex isolated from prochloron didemni retaining its chlorophyll a b light harvesting system
Proceedings of the National Academy of Sciences of the United States of America, 2003Co-Authors: Thomas S. Bibby, Anthony W. D. Larkum, Jon Nield, Min Chen, James BarberAbstract:Abstract Prochlorophytes are a class of cyanobacteria that do not use phycobiliproteins as light-harvesting systems, but contain chlorophyll (Chl) a/b-binding Pcb proteins. Recently it was shown that Pcb proteins form an 18-subunit light-harvesting antenna ring around the photosystem I (PSI) trimeric reaction center complex of the prochlorophyte Prochlorococcus marinus SS120. Here we have investigated whether the symbiotic prochlorophyte Prochloron didemni also contains the same supermolecular complex. Using cells isolated directly from its ascidian host, we found no evidence for the presence of the Pcb–PSI supercomplex. Instead we have identified and characterized a supercomplex composed of photosystem II (PSII) and Pcb proteins. We show that 10-Pcb subunits associate with the PSII dimeric reaction center core to form a giant complex having an estimated Mr of 1,500 kDa with dimensions of 210 × 290 A. Five-Pcb subunits flank each long side of the dimer and assuming each binds 13 Chl molecules, increase the antenna size of PSII by ≈200%. Fluorescence emission studies indicate that energy transfer occurs efficiently from the Pcb antenna. Modeling using the x-ray structure of cyanobacterial PSII suggests that energy transfer to the PSII reaction center is via the Chls bound to the CP47 and CP43 proteins.
-
Structure of a photosystem II supercomplex isolated from Prochloron didemni retaining its chlorophyll a/b light-harvesting system
Proceedings of the National Academy of Sciences of the United States of America, 2003Co-Authors: Thomas S. Bibby, Anthony W. D. Larkum, Jon Nield, Min Chen, James BarberAbstract:Prochlorophytes are a class of cyanobacteria that do not use phycobiliproteins as light-harvesting systems, but contain chlorophyll (Chl) a/b-binding Pcb proteins. Recently it was shown that Pcb proteins form an 18-subunit light-harvesting antenna ring around the photosystem I (PSI) trimeric reaction center complex of the prochlorophyte Prochlorococcus marinus SS120. Here we have investigated whether the symbiotic prochlorophyte Prochloron didemni also contains the same supermolecular complex. Using cells isolated directly from its ascidian host, we found no evidence for the presence of the Pcb-PSI supercomplex. Instead we have identified and characterized a supercomplex composed of photosystem II (PSII) and Pcb proteins. We show that 10-Pcb subunits associate with the PSII dimeric reaction center core to form a giant complex having an estimated Mr of 1,500 kDa with dimensions of 210 x 290 A. Five-Pcb subunits flank each long side of the dimer and assuming each binds 13 Chl molecules, increase the antenna size of PSII by approximately 200%. Fluorescence emission studies indicate that energy transfer occurs efficiently from the Pcb antenna. Modeling using the x-ray structure of cyanobacterial PSII suggests that energy transfer to the PSII reaction center is via the Chls bound to the CP47 and CP43 proteins.
-
chlorophyll d as the major photopigment in acaryochloris marina
Journal of Porphyrins and Phthalocyanines, 2002Co-Authors: Min Chen, Rosanne Quinnell, Anthony W. D. LarkumAbstract:Chlorophyll (Chl) d is the major pigment in the photosystems (PS) and light-harvesting complex(es) of Acaryochloris marina. Chl a is present in small and variable amounts in PSII and in the light-harvesting complex(es). Isolated PSII complex showed a major fluorescence emission peak at 725 nm and a smaller emission peak due to Chl d at 701 nm, while the PSI complex showed two pools of Chl d, one with emission at 730 nm and the other at 709 nm at 77 K. In PSI and PSII of classical cyanobacteria and of higher plants, where Chl a is the predominant pigment rather than Chl d, these differences are not as pronounced. Light energy absorbed by phycobiliproteins was also active in these Chl d emissions. The major light-harvesting pigment protein is similar to the prochlorophyte Chl-binding protein (pcb) and had a major emission peak at 711 nm. In Cyanobacteria an iron-stress induced Chl-binding protein (isiA) forms a polymeric ring around PSI, and so the effect(s) of iron stress on A. marina where investigated. No clear evidence could be deduced for the formation of an isiA protein under iron stress and no clear changes in the proportion of Chl d :Chl a could be discerned although phycobilins showed a decreased under iron-stress conditions. That Chl d replaces Chl a in all its functions in A. marina is clear; the advantage of this evolutionary development appears to be to enable A. marina to absorb far-red light which occurs in environments where red light is filtered out by other photosynthetic organisms.
Susan S. Golden - One of the best experts on this subject based on the ideXlab platform.
-
independent evolution of the prochlorophyte and green plant chlorophyll a b light harvesting proteins
Proceedings of the National Academy of Sciences of the United States of America, 1996Co-Authors: G W M Van Der Staay, Anthony W. D. Larkum, Roger G. Hiller, Susan S. Golden, Frederic Partensky, A Ducret, Ruedi Aebersold, R Li, Pamela M Wrench, Beverley R GreenAbstract:The Prochlorophytes are oxygenic prokaryotes differing from other cyanobacteria by the presence of a light-harvesting system containing both chlorophylls (Chls) a and b and by the absence of phycobilins. We demonstrate here that the Chl a/b binding proteins from all three known prochlorophyte genera are closely related to IsiA, a cyanobacterial Chl a-binding protein induced by iron starvation, and to CP43, a constitutively expressed Chl a antenna protein of photosystem II. The prochlorophyte Chl a/b protein (pcb) genes do not belong to the extended gene family encoding eukaryotic Chl a/b and Chl a/c light-harvesting proteins. Although higher plants and Prochlorophytes share common pigment complements, their light-harvesting systems have evolved independently.
-
Conserved relationship between psbH and petBD genes: presence of a shared upstream element in Prochlorothrix hollandica
Plant Molecular Biology, 1992Co-Authors: Karen L. Greer, Susan S. GoldenAbstract:Prochlorophytes are an unusual group of prokaryotic oxygenic photoautotrophs that morphologically appear to bridge the gap between cyanobacteria and the chloroplasts of eukaryotic plants. Molecular data place this group evolutionarily within the cyanobacteria, but they have a photosynthetic apparatus that is very similar to that found in chloroplasts. We have sequenced from the prochlorophyte Prochlorothrix hollandica a set of genes ( psbB, psbH, petB and petD ) that has a conserved organization in chloroplast genomes that is different from the organization in cyanobacterial genomes. The four genes are linked as an operon in chloroplasts, but only petB and petD are closely linked and cotranscribed in cyanobacteria. Although the prochlorophyte gene arrangement resembles that of cyanobacteria, one feature suggests the coordinated regulation of the unlinked genes. A 93 bp region of absolute conservation occurs upstream of the psbH gene and the petBD operon, near the site of transcription initiation in each gene set. This conserved element may indicate an alternative to cotranscription for achieving co-regulation of the psbH and petBD genes in the prochlorophyte.
-
Sequence analysis and phylogenetic reconstruction of the genes encoding the large and small subunits of ribulose-1,5-bisphosphate carboxylase/oxygenase from the chlorophyllb-containing prokaryoteProchlorothrix hollandica
Journal of Molecular Evolution, 1991Co-Authors: Susan S. GoldenAbstract:Prochlorophytes similar to Prochloron sp. and Prochlorothrix hollandica have been suggested as possible progenitors of the plastids of green algae and land plants because they are prokaryotic organisms that possess chlorophyll b (chl b ). We have sequenced the Prochlorothrix genes encoding the large and small subunits of ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco), rbcL and rbcS , for comparison with those of other taxa to assess the phylogenetic relationship of this species. Length differences in the large subunit polypeptide among all sequences compared occur primarily at the amino terminus, where numerous short gaps are present, and at the carboxy terminus, where sequences of Alcaligenes eutrophus and non-chlorophyll b algae are several amino acids longer. Some domains in the small subunit polypeptide are conserved among all sequences analyzed, yet in other domains the sequences of different phylogenetic groups exhibit specific structural characteristics. Phylogenetic analyses of rbcL and rbcS using Wagner parsimony analysis of deduced amino acid sequences indicate that Prochlorothrix is more closely related to cyanobacteria than to the green plastid lineage. The molecular phylogenies suggest that plastids originated by at least three separate primary endosymbiotic events, i.e., once each leading to green algae and land plants, to red algae, and to Cyanophora paradoxa . The Prochlorothrix rubisco genes show a strong GC bias, with 68% of the third codon positions being G or C. Factors that may affect the GC content of different genomes are discussed.
Richard C Zimmerman - One of the best experts on this subject based on the ideXlab platform.
-
C (2006), ‘Red and black tides: Quantitative analysis of water-leaving radiance and perceived color for phytoplankton, colored dissolved organic matter, and suspended sediments’, Limnology and Oceanography
2016Co-Authors: Heidi M Dierssen, Raphael M. Kudela, John P Ryan, Richard C ZimmermanAbstract:Using field measurements and quantitative modeling, we demonstrate that red coloration of the sea surface is not associated with any particular group of phytoplankton and is strongly dependent on the physiology of the human visual system. Red or brown surface waters can be produced by high concentrations of most types of algae, colored dissolved organic matter, or suspended sediment. Even though light reflected by red tides commonly peaks in the yellow spectral region (570–580 nm), human color perception requires consideration of the entire spectrum of light relative to receptors within the human eye. The color shift from green to red is not due to any special optical properties of the algae but results from an overlap in spectral response of the eye’s red and green cones (centered at 564 and 534 nm, respectively). The spectral peak in light reflected from dense algal blooms coincides with a critical hinge point in color vision (570–580 nm), where fine-scale shifts in the spectral shape of water-leaving radiance due to algal absorption and backscattering properties lead to pronounced variations in the observed color. Of the taxa considered, only Chlorophytes and Prochlorophytes lacked sufficient accessory pigments to produce a red tide. Chlorophyll fluorescence and enhanced near-infrared reflectance (the ‘‘red edge’’) contribute negligibly to the perceived color. Black water events are produced when water is highly absorbing but lacks backscattering constituents
-
Red and black tides: Quantitative analysis of water-leaving radiance and perceived color for phytoplankton, colored dissolved organic matter, and suspended sediments
Limnology and Oceanography, 2006Co-Authors: Heidi M Dierssen, Raphael M. Kudela, John P Ryan, Richard C ZimmermanAbstract:Using field measurements and quantitative modeling, we demonstrate that red coloration of the sea surface is not associated with any particular group of phytoplankton and is strongly dependent on the physiology of the human visual system. Red or brown surface waters can be produced by high concentrations of most types of algae, colored dissolved organic matter, or suspended sediment. Even though light reflected by red tides commonly peaks in the yellow spectral region (570-580 nm), human color perception requires consideration of the entire spectrum of light relative to receptors within the human eye. The color shift from green to red is not due to any special optical properties of the algae but results from an overlap in spectral response of the eye's red and green cones (centered at 564 and 534 nm, respectively). The spectral peak in light reflected from dense algal blooms coincides with a critical hinge point in color vision (570-580 nm), where fine-scale shifts in the spectral shape of water-leaving radiance due to algal absorption and backscattering properties lead to pronounced variations in the observed color. Of the taxa considered, only Chlorophytes and Prochlorophytes lacked sufficient accessory pigments to produce a red tide. Chlorophyll fluorescence and enhanced near-infrared reflectance (the "red edge") contribute negligibly to the perceived color. Black water events are produced when water is highly absorbing but lacks backscattering constituents.
James Barber - One of the best experts on this subject based on the ideXlab platform.
-
structure of a photosystem ii supercomplex isolated from prochloron didemni retaining its chlorophyll a b light harvesting system
Proceedings of the National Academy of Sciences of the United States of America, 2003Co-Authors: Thomas S. Bibby, Anthony W. D. Larkum, Jon Nield, Min Chen, James BarberAbstract:Abstract Prochlorophytes are a class of cyanobacteria that do not use phycobiliproteins as light-harvesting systems, but contain chlorophyll (Chl) a/b-binding Pcb proteins. Recently it was shown that Pcb proteins form an 18-subunit light-harvesting antenna ring around the photosystem I (PSI) trimeric reaction center complex of the prochlorophyte Prochlorococcus marinus SS120. Here we have investigated whether the symbiotic prochlorophyte Prochloron didemni also contains the same supermolecular complex. Using cells isolated directly from its ascidian host, we found no evidence for the presence of the Pcb–PSI supercomplex. Instead we have identified and characterized a supercomplex composed of photosystem II (PSII) and Pcb proteins. We show that 10-Pcb subunits associate with the PSII dimeric reaction center core to form a giant complex having an estimated Mr of 1,500 kDa with dimensions of 210 × 290 A. Five-Pcb subunits flank each long side of the dimer and assuming each binds 13 Chl molecules, increase the antenna size of PSII by ≈200%. Fluorescence emission studies indicate that energy transfer occurs efficiently from the Pcb antenna. Modeling using the x-ray structure of cyanobacterial PSII suggests that energy transfer to the PSII reaction center is via the Chls bound to the CP47 and CP43 proteins.
-
Structure of a photosystem II supercomplex isolated from Prochloron didemni retaining its chlorophyll a/b light-harvesting system
Proceedings of the National Academy of Sciences of the United States of America, 2003Co-Authors: Thomas S. Bibby, Anthony W. D. Larkum, Jon Nield, Min Chen, James BarberAbstract:Prochlorophytes are a class of cyanobacteria that do not use phycobiliproteins as light-harvesting systems, but contain chlorophyll (Chl) a/b-binding Pcb proteins. Recently it was shown that Pcb proteins form an 18-subunit light-harvesting antenna ring around the photosystem I (PSI) trimeric reaction center complex of the prochlorophyte Prochlorococcus marinus SS120. Here we have investigated whether the symbiotic prochlorophyte Prochloron didemni also contains the same supermolecular complex. Using cells isolated directly from its ascidian host, we found no evidence for the presence of the Pcb-PSI supercomplex. Instead we have identified and characterized a supercomplex composed of photosystem II (PSII) and Pcb proteins. We show that 10-Pcb subunits associate with the PSII dimeric reaction center core to form a giant complex having an estimated Mr of 1,500 kDa with dimensions of 210 x 290 A. Five-Pcb subunits flank each long side of the dimer and assuming each binds 13 Chl molecules, increase the antenna size of PSII by approximately 200%. Fluorescence emission studies indicate that energy transfer occurs efficiently from the Pcb antenna. Modeling using the x-ray structure of cyanobacterial PSII suggests that energy transfer to the PSII reaction center is via the Chls bound to the CP47 and CP43 proteins.
Frederic Partensky - One of the best experts on this subject based on the ideXlab platform.
-
independent evolution of the prochlorophyte and green plant chlorophyll a b light harvesting proteins
Proceedings of the National Academy of Sciences of the United States of America, 1996Co-Authors: G W M Van Der Staay, Anthony W. D. Larkum, Roger G. Hiller, Susan S. Golden, Frederic Partensky, A Ducret, Ruedi Aebersold, R Li, Pamela M Wrench, Beverley R GreenAbstract:The Prochlorophytes are oxygenic prokaryotes differing from other cyanobacteria by the presence of a light-harvesting system containing both chlorophylls (Chls) a and b and by the absence of phycobilins. We demonstrate here that the Chl a/b binding proteins from all three known prochlorophyte genera are closely related to IsiA, a cyanobacterial Chl a-binding protein induced by iron starvation, and to CP43, a constitutively expressed Chl a antenna protein of photosystem II. The prochlorophyte Chl a/b protein (pcb) genes do not belong to the extended gene family encoding eukaryotic Chl a/b and Chl a/c light-harvesting proteins. Although higher plants and Prochlorophytes share common pigment complements, their light-harvesting systems have evolved independently.
-
coexistence of phycoerythrin and a chlorophyll a b antenna in a marine prokaryote
Proceedings of the National Academy of Sciences of the United States of America, 1996Co-Authors: Wolfgang R. Hess, G W M Van Der Staay, Frederic Partensky, Jose Manuel Garciafernandez, Thomas Borner, Daniel VaulotAbstract:Abstract Prochlorococcus marinus CCMP 1375, a ubiquitous and ecologically important marine prochlorophyte, was bound to possess functional genes coding for the alpha and beta subunits of a phycobiliprotein. The latter is similar to phycoerythrins (PE) from marine Synechococcus cyanobacteria and bind a phycourobilin-like pigment as the major chromophore. However, differences in the sequences of the alpha and beta chains compared with known PE subunits and the presence of a single bilin attachment site on the alpha subunit designate it as a novel PE type, which we propose naming PE-III. P. marinus is the sole prokaryotic organisms known so far that contains chlorophylls a and b as well as phycobilins. These data strongly suggest that the common ancestor of Prochlorophytes and the Synechococcus cyanobacteria contained phycobilins. Flow cytometric data from the tropical Pacific Ocean provide evidence that deep populations of Prochlorococcus possess low amounts of a PE-like pigment, which could serve either in light harvesting or nitrogen storage or both.
-
photoacclimation of prochlorococcus sp prochlorophyta strains isolated from the north atlantic and the mediterranean sea
Plant Physiology, 1993Co-Authors: Frederic Partensky, Nicolas Hoepffner, Osvaldo Ulloa, Daniel VaulotAbstract:Two Atlantic (SARG and NATL1) strains and one Mediterranean (MED) strain of Prochlorococcus sp., a recently discovered marine, free-living prochlorophyte, were grown over a range of “white” irradiances (lg) and under low blue light to examine their photoacclimation capacity. All three strains contained divinyl (DV) chlorophylls (Chl) a and b, both distinguishable from “normal” Chls by their red-shifted blue absorption maximum, a Chl c-like pigment at low concentration, zeaxanthin, and [alpha]-carotene. The presence of two phaeophytin b peaks in acidified extracts from both Atlantic strains grown at high lg suggests that these strains also had a normal Chl b-like pigment. In these strains, the total Chl b to DV-Chl a molar ratio decreased from about 1 at 7.5 [mu]mol quanta m-2 s-1 to 0.4 to 0.5 at 133 [mu]mol quanta m-2 s-1. In contrast, the MED strain always had a low DV-Chl b to DV-Chl a molar ratio, ranging between 0.13 at low lg and 0.08 at high lg. The discrepancies between the Atlantic and MED strains could result from differences either in the number of light-harvesting complexes (LHC) II per photosystem II or in the Chl b-binding capacity of the apoproteins constituting LHC II. Photosynthesis was saturated at approximately 5 fg C(fg Chl)-1 h-1 or 6 fg C cell-1 h-1, and growth was saturated at approximately 0.45 d-1 for both MED and SARG strains at 18[deg]C, but saturating irradiances differed between strains. Atlantic strains exhibited increased light-saturated rates and quantum yield for carbon fixation under blue light.
-
cell cycle distributions of Prochlorophytes in the north western mediterranean sea
Deep-sea research. Part A. Oceanographic research papers, 1992Co-Authors: Daniel Vaulot, Frederic PartenskyAbstract:Abstract Natural populations of oceanic Prochlorophytes were sampled from the northwestern Mediterranean Sea in winter, stained with the DNA-specific fluorochrome DAPI, and analysed by flow cytometry. DNA histograms exhibited two peaks (G 1 and G 2 cells, containing one and two genome copies, respectively), separated by a trough of DNA-synthesizing cells (S cells). This suggested a cell cycle with a discrete S phase similar to that observed in eucaryotes or slow-growing procaryotes. Nitrogen and light were the two key environmental factors controlling the in situ cell cycle distributions of this procaryote. When nitrate levels were below 0.4 μM or light below 0.1% of the surface intensity, most of the cells were found in G 1 , suggesting that they were not actively cycling. Cells arrested in G 1 could be induced to cycle into S + G 2 by incubating them with added nitrogen. Response was a function of initial nitrate concentration and decreased with depth, indicating that it was modulated by available light. These findings strongly suggest that Prochlorophytes, which are one of the key components of the picoplankton community, may grow slowly in nitrogen-depleted waters, but still have the potential to respond quickly to nitrogen pulses.