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1.
Int J Mol Sci ; 20(15)2019 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-31357454

RESUMO

There are a number of highly conserved photosystem II light-harvesting antenna proteins in moss whose functions are unclear. Here, we investigated the involvement of chlorophyll-binding proteins, Lhcb6 and Lhcb5, in light-harvesting and photosynthesis regulation in Physcomitrella patens. Lhcb6 or Lhcb5 knock-out resulted in a disordered thylakoid arrangement, a decrease in the number of grana membranes, and an increase in the number of starch granule. The absence of Lhcb6 or Lhcb5 did not noticeably alter the electron transport rates. However, the non-photochemical quenching activity in the lhcb5 mutant was dramatically reduced when compared to wild-type or lhcb6 plants under abiotic stress. Lhcb5 plants were more sensitive to photo-inhibition, while lhcb6 plants showed little difference compared to the wild-type plants under high-light stress. Moreover, both mutants showed a growth malformation phenotype with reduced chlorophyll content in the gametophyte. These results suggested that Lhcb6 or Lhcb5 played a unique role in plant development, thylakoid organization, and photoprotection of PSII in Physcomitrella, especially when exposed to high light or osmotic environments.


Assuntos
Bryopsida/fisiologia , Regulação da Expressão Gênica de Plantas , Complexos de Proteínas Captadores de Luz/genética , Fotossíntese , Estresse Fisiológico , Bryopsida/citologia , Bryopsida/ultraestrutura , Cloroplastos/genética , Cloroplastos/metabolismo , Imunofluorescência , Regulação da Expressão Gênica de Plantas/efeitos da radiação , Técnicas de Silenciamento de Genes , Luz , Complexos de Proteínas Captadores de Luz/metabolismo , Mutação , Fenótipo , Complexo de Proteína do Fotossistema II/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Transporte Proteico
2.
Planta ; 250(2): 589-601, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31134341

RESUMO

MAIN CONCLUSION: The absence of state transitions in a Nt(Hn) cybrid is due to a cleavage of the threonine residue from the misprocessed N-terminus of the LHCII polypeptides. The cooperation between the nucleus and chloroplast genomes is essential for plant photosynthetic fitness. The rapid and specific interactions between nucleus-encoded and chloroplast-encoded proteins are under intense investigation with potential for applications in agriculture and renewable energy technology. Here, we present a novel model for photosynthesis research in which alien henbane (Hyoscyamus niger) chloroplasts function on the nuclear background of a tobacco (Nicotiana tabacum). The result of this coupling is a cytoplasmic hybrid (cybrid) with inhibited state transitions-a mechanism responsible for balancing energy absorption between photosystems. Protein analysis showed differences in the LHCII composition of the cybrid plants. SDS-PAGE analysis revealed a novel banding pattern in the cybrids with at least one additional 'LHCII' band compared to the wild-type parental species. Proteomic work suggested that the N-terminus of at least some of the cybrid Lhcb proteins was missing. These findings provide a mechanistic explanation for the lack of state transitions-the N-terminal truncation of the Lhcb proteins in the cybrid included the threonine residue that is phosphorylated/dephosphorylated in order to trigger state transitions and therefore crucial energy balancing mechanism in plants.


Assuntos
Genoma de Cloroplastos/genética , Genoma de Planta/genética , Complexos de Proteínas Captadores de Luz/metabolismo , Tabaco/genética , Núcleo Celular/metabolismo , Cloroplastos/metabolismo , Complexos de Proteínas Captadores de Luz/genética , Fosforilação , Fotossíntese , Complexo de Proteína do Fotossistema II/genética , Complexo de Proteína do Fotossistema II/metabolismo , Proteômica , Treonina/metabolismo , Tabaco/fisiologia
3.
Gene ; 702: 171-181, 2019 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-30943438

RESUMO

The light-harvesting chlorophyll a/b-binding (Lhc) superfamily, composed of several distinct antennae protein families, plays essential roles in light capture and photoprotection in plants. Compared with the extensive research in Arabidopsis thaliana and certain species, little is known about this superfamily in cassava (Manihot esculenta), an Euphorbiaceous plant experienced one so-called ρ recent whole-genome duplication (WGD). This study presents the first genome-wide identification of Lhc supergene family in cassava, resulting in 35 members that are distributed across 15 chromosomes. Phylogenetic analysis and BRH (Best Reciprocal Hit)-based sequence comparison assigned these genes into four previously defined families and 26 orthologous groups (including one absent from Arabidopsis). Synteny analysis showed that nine identified duplicates were derived from the WGD as well as local duplication, and retention bias of WGD duplicates in this species was shown to be something different from that in Arabidopsis which experienced two recent WGDs. Transcriptional profiling of MeLhc superfamily genes revealed a predominant expression pattern in green tissues such as leaf and midvein. Moreover, comparison of exon-intron structures, protein motifs, and gene expression profiles revealed divergence of duplicate pairs. Our findings will not only improve our knowledge on the evolution of this superfamily in cassava, but also provide valuable information for further functional studies.


Assuntos
Complexos de Proteínas Captadores de Luz/genética , Manihot/genética , Família Multigênica , Motivos de Aminoácidos , Mapeamento Cromossômico , Éxons , Genômica , Íntrons , Complexos de Proteínas Captadores de Luz/química , Complexos de Proteínas Captadores de Luz/classificação , Complexos de Proteínas Captadores de Luz/metabolismo , Manihot/metabolismo , Filogenia , Sintenia
4.
Nat Plants ; 5(3): 263-272, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30850820

RESUMO

Photosystem I (PSI) is a highly efficient natural light-energy converter, and has diverse light-harvesting antennas associated with its core in different photosynthetic organisms. In green algae, an extremely large light-harvesting complex I (LHCI) captures and transfers energy to the PSI core. Here, we report the structure of PSI-LHCI from a green alga Bryopsis corticulans at 3.49 Å resolution, obtained by single-particle cryo-electron microscopy, which revealed 13 core subunits including subunits characteristic of both prokaryotes and eukaryotes, and 10 light-harvesting complex a (Lhca) antennas that form a double semi-ring and an additional Lhca dimer, including a novel four-transmembrane-helix Lhca. In total, 244 chlorophylls were identified, some of which were located at key positions for the fast energy transfer. These results provide a firm structural basis for unravelling the mechanisms of light-energy harvesting, transfer and quenching in the green algal PSI-LHCI, and important clues as to how PSI-LHCI has changed during evolution.


Assuntos
Clorófitas/química , Complexos de Proteínas Captadores de Luz/química , Complexo de Proteína do Fotossistema I/química , Proteínas de Algas/química , Proteínas de Algas/metabolismo , Carotenoides/química , Carotenoides/metabolismo , Clorofila/química , Clorofila/metabolismo , Clorófitas/genética , Microscopia Crioeletrônica , Transferência de Energia , Evolução Molecular , Complexos de Proteínas Captadores de Luz/genética , Complexos de Proteínas Captadores de Luz/isolamento & purificação , Complexos de Proteínas Captadores de Luz/metabolismo , Modelos Moleculares , Complexo de Proteína do Fotossistema I/genética , Complexo de Proteína do Fotossistema I/isolamento & purificação , Complexo de Proteína do Fotossistema I/metabolismo , Multimerização Proteica , Subunidades Proteicas/química , Subunidades Proteicas/metabolismo
5.
Nat Plants ; 5(1): 34-40, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30598533

RESUMO

Light is essential for photosynthesis, but the amounts of light that exceed an organism's assimilation capacity can cause serious damage1. Photosynthetic organisms minimize such potential harm through protection mechanisms collectively referred to as non-photochemical quenching2. One mechanism of non-photochemical quenching called energy-dependent quenching (qE quenching) is readily activated under high-light conditions and dissipates excess energy as heat. LIGHT-HARVESTING COMPLEX STRESS-RELATED PROTEINS 1 and 3 (LHCSR1 and LHCSR3) have been proposed to mediate qE quenching in the green alga Chlamydomonas reinhardtii when grown under high-light conditions3. LHCSR3 induction requires a blue-light photoreceptor, PHOTOTROPIN (PHOT)4, although the signal transduction pathway between PHOT and LHCSR3 is not yet clear. Here, we identify two phot suppressor loci involved in qE quenching: de-etiolated 1 (det1)5 and damaged DNA-binding 1 (ddb1)6. Using a yeast two-hybrid analysis and an inhibitor assay, we determined that these two genetic elements are part of a protein complex containing CULLIN 4 (CUL4). These findings suggest a photoprotective role for the putative E3 ubiquitin ligase CUL4-DDB1DET1 in unicellular photosynthetic organisms that may mediate blue-light signals to LHCSR1 and LHCSR3 gene expression.


Assuntos
Chlamydomonas reinhardtii/fisiologia , Proteínas de Plantas/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Estiolamento , Regulação da Expressão Gênica de Plantas , Teste de Complementação Genética , Luz , Complexos de Proteínas Captadores de Luz/genética , Complexos de Proteínas Captadores de Luz/metabolismo , Mutação , Proteínas de Plantas/genética , Técnicas do Sistema de Duplo-Híbrido , Ubiquitina-Proteína Ligases/genética
6.
Methods ; 155: 30-40, 2019 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-30503825

RESUMO

Transcripts have intrinsic propensity to form stable secondary structure that is fundamental to regulate RNA transcription, splicing, translation, RNA localization and turnover. Numerous methods that integrate chemical reactions with next-generation sequencing (NGS) have been applied to study in vivo RNA structure, providing new insights into RNA biology. Dimethyl sulfate (DMS) probing coupled with mutational profiling through NGS (DMS-MaPseq) is a newly developed method for revealing genome-wide or target-specific RNA structure. Herein, we present our experimental protocol of a modified DMS-MaPseq method for plant materials. The DMS treatment condition was optimized, and library preparation procedures were simplified. We also provided custom scripts for bioinformatic analysis of genome-wide DMS-MaPseq data. Bioinformatic results showed that our method could generate high-quality and reproducible data. Further, we assessed sequencing depth and coverage for genome-wide RNA structure profiling in Arabidopsis, and provided two examples of in vivo structure of mobile RNAs. We hope that our modified DMS-MaPseq method will serve as a powerful tool for analyzing in vivo RNA structurome in plants.


Assuntos
Arabidopsis/genética , Biologia Computacional/métodos , Genoma de Planta , Sequenciamento de Nucleotídeos em Larga Escala/métodos , RNA Mensageiro/química , RNA de Plantas/química , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Pareamento de Bases , Sequência de Bases , Complexos de Proteínas Captadores de Luz/genética , Complexos de Proteínas Captadores de Luz/metabolismo , Mutação , Conformação de Ácido Nucleico , Complexo de Proteína do Fotossistema II/genética , Complexo de Proteína do Fotossistema II/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , RNA de Plantas/genética , RNA de Plantas/metabolismo , Ésteres do Ácido Sulfúrico/química
7.
FEBS Lett ; 593(2): 163-174, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30485416

RESUMO

In Photosystem II, loop E of the chlorophyll-binding CP47 protein is located near a redox-active tyrosine, YD , forming a symmetrical analog to loop E in CP43, which provides a ligand to the oxygen-evolving complex (OEC). A Glu364 to Gln substitution in CP47, near YD , does not affect growth in the cyanobacterium Synechocystis sp. PCC 6803; however, deletion of the extrinsic protein PsbV in this mutant leads to a strain displaying a pH-sensitive phenotype. Using thermoluminescence, chlorophyll fluorescence, and flash-induced oxygen evolution analyses, we demonstrate that Glu364 influences the stability of YD and the redox state of the OEC, and highlight the effects of external pH on photosynthetic electron transfer in intact cyanobacterial cells.


Assuntos
Substituição de Aminoácidos , Clorofila/metabolismo , Complexos de Proteínas Captadores de Luz/química , Complexos de Proteínas Captadores de Luz/metabolismo , Complexo de Proteína do Fotossistema II/química , Complexo de Proteína do Fotossistema II/metabolismo , Synechocystis/metabolismo , Ácido Glutâmico/metabolismo , Glutamina/metabolismo , Ligações de Hidrogênio , Concentração de Íons de Hidrogênio , Complexos de Proteínas Captadores de Luz/genética , Modelos Moleculares , Oxirredução , Complexo de Proteína do Fotossistema II/genética , Ligação Proteica , Synechocystis/genética , Tirosina/metabolismo
8.
Biochim Biophys Acta Bioenerg ; 1860(3): 209-223, 2019 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-30414933

RESUMO

The light-harvesting 2 complex (LH2) of the purple phototrophic bacterium Rhodobacter sphaeroides is a highly efficient, light-harvesting antenna that allows growth under a wide-range of light intensities. In order to expand the spectral range of this antenna complex, we first used a series of competition assays to measure the capacity of the non-native pigments 3-acetyl chlorophyll (Chl) a, Chl d, Chl f or bacteriochlorophyll (BChl) b to replace native BChl a in the B800 binding site of LH2. We then adjusted the B800 site and systematically assessed the binding of non-native pigments. We find that Arg-10 of the LH2 ß polypeptide plays a crucial role in binding specificity, by providing a hydrogen-bond to the 3-acetyl group of native and non-native pigments. Reconstituted LH2 complexes harbouring the series of (B)Chls were examined by transient absorption and steady-state fluorescence spectroscopies. Although slowed 10-fold to ~6 ps, energy transfer from Chl a to B850 BChl a remained highly efficient. We measured faster energy-transfer time constants for Chl d (3.5 ps) and Chl f (2.7 ps), which have red-shifted absorption maxima compared to Chl a. BChl b, red-shifted from the native BChl a, gave extremely rapid (≤0.1 ps) transfer. These results show that modified LH2 complexes, combined with engineered (B)Chl biosynthesis pathways in vivo, have potential for retaining high efficiency whilst acquiring increased spectral range.


Assuntos
Complexos de Proteínas Captadores de Luz/genética , Engenharia de Proteínas , Rhodobacter sphaeroides/química , Bacterioclorofila A/metabolismo , Bacterioclorofilas/metabolismo , Sítios de Ligação/genética , Ligação Proteica , Rhodobacter sphaeroides/genética , Espectrometria de Fluorescência
9.
Int J Mol Sci ; 19(10)2018 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-30262721

RESUMO

To evaluate the effect of changes in chlorophyll (Chl) composition and fluorescence on final yield formation, early senescence leaf (esl) mutant rice and its wild-type cultivar were employed to investigate the genotype-dependent differences in Chl composition, Chl fluorescence, and yield characteristics during the grain-filling stage. However, the temporal expression patterns of key genes involved in the photosystem II (PSII) reaction center in the leaves of two rice genotypes were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). Results showed that the seed-setting rate, 1000-grain weight, and yield per plant remarkably decreased, and the increase in the 1000-grain weight during the grain-filling stage was retarded in esl mutant rice. Chl composition, maximal fluorescence yield (Fm), variable fluorescence (Fv), a maximal quantum yield of PSII photochemistry (Fv/Fm), and net photosynthetic rate (Pn) in esl mutant rice considerably decreased, thereby indicating the weakened abilities of light energy harvesting and transferring in senescent leaves. The esl mutant rice showed an increase in the minimal fluorescence yield (F0) and 1 - Fv/Fm and decreases in the expression levels of light-harvesting Chl a/b binding protein (Cab) and photosystem II binding protein A (PsbA), PsbB, PsbC, and PsbD encoding for the reaction center of the PSII complex during the grain-filling stage. These results indicated the PSII reaction centers were severely damaged in the mesophyll cells of senescent leaves, which resulted in the weakened harvesting quantum photon and transferring light energy to PSI and PSII for carbon dioxide assimilation, leading to enhanced heat dissipation of light energy and a decrease in Pn.


Assuntos
Clorofila/genética , Grão Comestível/genética , Mutação , Oryza/genética , Fotossíntese , Clorofila/química , Clorofila/metabolismo , Grão Comestível/crescimento & desenvolvimento , Grão Comestível/metabolismo , Fluorescência , Complexos de Proteínas Captadores de Luz/genética , Complexos de Proteínas Captadores de Luz/metabolismo , Oryza/crescimento & desenvolvimento , Oryza/metabolismo , Folhas de Planta/genética , Folhas de Planta/metabolismo
10.
Mol Microbiol ; 110(3): 325-334, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-29995316

RESUMO

Facultative phototrophic bacteria like Rhodobacter sphaeroides can produce ATP by anoxygenic photosynthesis, which is of advantage under conditions with limiting oxygen. However, the simultaneous presence of pigments, light and oxygen leads to the generation of harmful singlet oxygen. In order to avoid this stress situation, the formation of photosynthetic complexes is tightly regulated by light and oxygen signals. In a complex regulatory network several regulatory proteins and the small non-coding RNA PcrZ contribute to the balanced expression of photosynthesis genes. With PcrX this study identifies a second sRNA that is part of this network. The puf operon encodes pigment binding proteins of the light-harvesting I complex (PufBA) and of the reaction center (PufLM), a protein regulating porphyrin flux (PufQ), and a scaffolding protein (PufX). The PcrX sRNA is derived from the 3' UTR of the puf operon mRNA by RNase E-mediated cleavage. It targets the pufX mRNA segment, reduces the half-life of the pufBALMX mRNA and as a consequence affects the level of photosynthetic complexes. By its action PcrX counteracts the increased expression of photosynthesis genes that is mediated by protein regulators and is thus involved in balancing the formation of photosynthetic complexes in response to external stimuli.


Assuntos
Regiões 3' não Traduzidas , Proteínas de Bactérias/biossíntese , Regulação Bacteriana da Expressão Gênica , Complexos de Proteínas Captadores de Luz/biossíntese , Fotossíntese , Pequeno RNA não Traduzido/metabolismo , Rhodobacter sphaeroides/metabolismo , Proteínas de Bactérias/genética , Complexos de Proteínas Captadores de Luz/genética , Óperon , Pequeno RNA não Traduzido/genética , Rhodobacter sphaeroides/genética
11.
Proc Natl Acad Sci U S A ; 115(30): E7015-E7022, 2018 07 24.
Artigo em Inglês | MEDLINE | ID: mdl-29987047

RESUMO

Robust molecular tool kits in model and industrial microalgae are key to efficient targeted manipulation of endogenous and foreign genes in the nuclear genome for basic research and, as importantly, for the development of algal strains to produce renewable products such as biofuels. While Cas9-mediated gene knockout has been demonstrated in a small number of algal species with varying efficiency, the ability to stack traits or generate knockout mutations in two or more loci are often severely limited by selectable agent availability. This poses a critical hurdle in developing production strains, which require stacking of multiple traits, or in probing functionally redundant gene families. Here, we combine Cas9 genome editing with an inducible Cre recombinase in the industrial alga Nannochloropsis gaditana to generate a strain, NgCas9+Cre+, in which the potentially unlimited stacking of knockouts and addition of new genes is readily achievable. Cre-mediated marker recycling is first demonstrated in the removal of the selectable marker and GFP reporter transgenes associated with the Cas9/Cre construct in NgCas9+Cre+ Next, we show the proof-of-concept generation of a markerless knockout in a gene encoding an acyl-CoA oxidase (Aco1), as well as the markerless recapitulation of a 2-kb insert in the ZnCys gene 5'-UTR, which results in a doubling of wild-type lipid productivity. Finally, through an industrially oriented process, we generate mutants that exhibit up to ∼50% reduction in photosynthetic antennae size by markerless knockout of seven genes in the large light-harvesting complex gene family.


Assuntos
Acil-CoA Oxidase , Sistemas CRISPR-Cas , Edição de Genes , Lipídeos , Característica Quantitativa Herdável , Estramenópilas , Acil-CoA Oxidase/genética , Acil-CoA Oxidase/metabolismo , Complexos de Proteínas Captadores de Luz/genética , Complexos de Proteínas Captadores de Luz/metabolismo , Lipídeos/biossíntese , Lipídeos/genética , Estramenópilas/genética , Estramenópilas/metabolismo
12.
Biochim Biophys Acta Bioenerg ; 1859(9): 676-683, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29981721

RESUMO

In natural variable environments, plants rapidly adjust photosynthesis for optimum balance between photochemistry and photoprotection. These adjustments mainly occur via changes in their proton motive force (pmf). Recent studies based on time resolved analysis of the Electro Chromic Signal (ECS) bandshift of photosynthetic pigments in the model plant Arabidopsis thaliana have suggested an active role of ion fluxes across the thylakoid membranes in the regulation of the pmf. Among the different channels and transporters possibly involved in this phenomenon, we previously identified the TPK3 potassium channel. Plants silenced for TPK3 expression displayed light stress signatures, with reduced Non Photochemical Quenching (NPQ) capacity and sustained anthocyanin accumulation, even at moderate intensities. In this work we re-examined the role of this protein in pmf regulation, starting from the observation that both TPK3 knock-down (TPK3 KD) and WT plants display enhanced anthocyanin accumulation in the light under certain growth conditions, especially in old leaves. We thus compared the pmf features of young "green" (without anthocyanins) and old "red" (with anthocyanins) leaves in both genotypes using a global fit analysis of the ECS. We found that the differences in the ECS profile measured between the two genotypes reflect not only differences in TPK3 expression level, but also a modified photosynthetic activity of stressed red leaves, which are present in a larger amounts in the TPK3 KD plants.


Assuntos
Arabidopsis/metabolismo , Clorofila/metabolismo , Complexos de Proteínas Captadores de Luz/metabolismo , Plantas Geneticamente Modificadas/metabolismo , Canais de Potássio/metabolismo , Força Próton-Motriz , Arabidopsis/genética , Arabidopsis/efeitos da radiação , Luz , Complexos de Proteínas Captadores de Luz/genética , Fotossíntese , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/efeitos da radiação , Canais de Potássio/genética , Tilacoides/metabolismo
13.
J Phys Chem Lett ; 9(12): 3278-3284, 2018 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-29863354

RESUMO

The uphill excitation energy transfer (EET) from the core antenna (LH1) to the reaction center (RC) of purple photosynthetic bacteria was investigated at room temperature by comparing the native LH1-RC from Thermochromatium ( Tch.) tepidum with the hybrid LH1-RC from a mutant strain of Rhodobacter ( Rba.) sphaeroides. The latter protein with chimeric Tch-LH1 and Rba-RC exhibits a substantially larger RC-to-LH1 energy difference (Δ E = 630 cm-1) of 3-fold thermal energy (3 kB T). The spectroscopic and kinetics results are discussed on the basis of the newly reported high-resolution structures of Tch. tepidum LH1-RC, which allow us to propose the existence of a passage formed by LH1 BChls that facilitates the LH1 → RC EET. The semilogarithmic plot of the EET rate against Δ E was found to be linear over a broad range of Δ E, which consolidates the mechanism of thermal activation as promoted by the spectral overlap between the LH1 fluorescence and the special pair absorption of RC.


Assuntos
Proteínas de Bactérias/metabolismo , Chromatiaceae/metabolismo , Complexos de Proteínas Captadores de Luz/metabolismo , Rhodobacter sphaeroides/metabolismo , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Bacterioclorofilas/química , Transferência de Energia , Complexos de Proteínas Captadores de Luz/química , Complexos de Proteínas Captadores de Luz/genética , Mutagênese , Estrutura Terciária de Proteína , Espectrometria de Fluorescência
14.
Harmful Algae ; 75: 27-34, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29778223

RESUMO

PCP and acpPC are the two major antennae proteins that bind pigments in peridinin-containing dinoflagellates. The relationship between antennae proteins and cellular pigments at molecular level is still poorly understood. Here we identified and characterized the two antennae protein genes in dinoflagellate Prorocentrum donghaiense under different light conditions. The mature PCP protein was 32 kDa, while acpPC was a polyprotein each of 19 kDa. Both genes showed higher expression under low light than under high light, suggesting their possible role in a low light adaptation mechanism. The two genes showed differential diel expression rhythm, with PCP being more highly expressed in the dark than in the light period and acpPC the other way around. HPLC analysis of cellular pigments indicated a diel change of chlorophyll c2, but invariability of other pigments. A stable peridinin: chlorophyll a pigment ratio was detected under different light intensities and over the diel cycle, although the diadinoxanthin:chlorophyll a ratio increased significantly with light intensity. The results suggest that 1) PCP and acpPC genes are functionally distinct, 2) PCP and acpPC can function under low light as an adaptive mechanism in P. donghaiense, 3). the ratios of diadinoxanthin:chlorophyll a and peridinin: chlorophyll a can potentially be used as an indicator of algal photophysiological status and a pigment signature respectively under different light conditions in P. donghaiense.


Assuntos
Proteínas de Algas/genética , Relógios Circadianos , Dinoflagelados/fisiologia , Complexos de Proteínas Captadores de Luz/genética , Pigmentos Biológicos/química , Luz Solar , Proteínas de Algas/metabolismo , Dinoflagelados/genética
15.
Plant Physiol ; 177(3): 953-965, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29773581

RESUMO

Marine diatoms are prominent phytoplankton organisms that perform photosynthesis in extremely variable environments. Diatoms possess a strong ability to dissipate excess absorbed energy as heat via nonphotochemical quenching (NPQ). This process relies on changes in carotenoid pigment composition (xanthophyll cycle) and on specific members of the light-harvesting complex family specialized in photoprotection (LHCXs), which potentially act as NPQ effectors. However, the link between light stress, NPQ, and the existence of different LHCX isoforms is not understood in these organisms. Using picosecond fluorescence analysis, we observed two types of NPQ in the pennate diatom Phaeodactylum tricornutum that were dependent on light conditions. Short exposure of low-light-acclimated cells to high light triggers the onset of energy quenching close to the core of photosystem II, while prolonged light stress activates NPQ in the antenna. Biochemical analysis indicated a link between the changes in the NPQ site/mechanism and the induction of different LHCX isoforms, which accumulate either in the antenna complexes or in the core complex. By comparing the responses of wild-type cells and transgenic lines with a reduced expression of the major LHCX isoform, LHCX1, we conclude that core complex-associated NPQ is more effective in photoprotection than is the antenna complex. Overall, our data clarify the complex molecular scenario of light responses in diatoms and provide a rationale for the existence of a degenerate family of LHCX proteins in these algae.


Assuntos
Diatomáceas/fisiologia , Complexos de Proteínas Captadores de Luz/metabolismo , Aclimatação , Clorofila/metabolismo , Cloroplastos/metabolismo , Diatomáceas/citologia , Fluorescência , Regulação da Expressão Gênica , Técnicas de Silenciamento de Genes , Luz , Complexos de Proteínas Captadores de Luz/genética , Organismos Geneticamente Modificados , Processos Fotoquímicos , Complexo de Proteína do Fotossistema II/genética , Complexo de Proteína do Fotossistema II/metabolismo , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo
16.
Nat Commun ; 9(1): 1568, 2018 04 19.
Artigo em Inglês | MEDLINE | ID: mdl-29674684

RESUMO

Photosynthetic prokaryotes evolved diverse light-harvesting (LH) antennas to absorb sunlight and transfer energy to reaction centers (RC). The filamentous anoxygenic phototrophs (FAPs) are important early branching photosynthetic bacteria in understanding the origin and evolution of photosynthesis. How their photosynthetic machinery assembles for efficient energy transfer is yet to be elucidated. Here, we report the 4.1 Å structure of photosynthetic core complex from Roseiflexus castenholzii by cryo-electron microscopy. The RC-LH complex has a tetra-heme cytochrome c bound RC encompassed by an elliptical LH ring that is assembled from 15 LHαß subunits. An N-terminal transmembrane helix of cytochrome c inserts into the LH ring, not only yielding a tightly bound cytochrome c for rapid electron transfer, but also opening a slit in the LH ring, which is further flanked by a transmembrane helix from a newly discovered subunit X. These structural features suggest an unusual quinone exchange model of prokaryotic photosynthetic machinery.


Assuntos
Proteínas de Bactérias/química , Chloroflexi/metabolismo , Complexos de Proteínas Captadores de Luz/química , Complexo de Proteínas do Centro de Reação Fotossintética/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Chloroflexi/química , Chloroflexi/genética , Chloroflexi/efeitos da radiação , Microscopia Crioeletrônica , Citocromos c/química , Citocromos c/genética , Citocromos c/metabolismo , Heme/química , Heme/metabolismo , Luz , Complexos de Proteínas Captadores de Luz/genética , Complexos de Proteínas Captadores de Luz/metabolismo , Modelos Moleculares , Complexo de Proteínas do Centro de Reação Fotossintética/genética , Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo
17.
Biochim Biophys Acta Bioenerg ; 1859(9): 666-675, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29548769

RESUMO

Non-photochemical quenching (NPQ) of chlorophyll fluorescence is the process by which excess light energy is harmlessly dissipated within the photosynthetic membrane. The fastest component of NPQ, known as energy-dependent quenching (qE), occurs within minutes, but the site and mechanism of qE remain of great debate. Here, the chlorophyll fluorescence of Arabidopsis thaliana wild type (WT) plants was compared to mutants lacking all minor antenna complexes (NoM). Upon illumination, NoM exhibits altered chlorophyll fluorescence quenching induction (i.e. from the dark-adapted state) characterised by three different stages: (i) a fast quenching component, (ii) transient fluorescence recovery and (iii) a second quenching component. The initial fast quenching component originates in light harvesting complex II (LHCII) trimers and is dependent upon PsbS and the formation of a proton gradient across the thylakoid membrane (ΔpH). Transient fluorescence recovery is likely to occur in both WT and NoM plants, but it cannot be overcome in NoM due to impaired ΔpH formation and a reduced zeaxanthin synthesis rate. Moreover, an enhanced fluorescence emission peak at ~679 nm in NoM plants indicates detachment of LHCII trimers from the bulk antenna system, which could also contribute to the transient fluorescence recovery. Finally, the second quenching component is triggered by both ΔpH and PsbS and enhanced by zeaxanthin synthesis. This study indicates that minor antenna complexes are not essential for qE, but reveals their importance in electron stransport, ΔpH formation and zeaxanthin synthesis.


Assuntos
Arabidopsis/metabolismo , Clorofila/metabolismo , Fluorescência , Complexos de Proteínas Captadores de Luz/metabolismo , Folhas de Planta/metabolismo , Plantas Geneticamente Modificadas/metabolismo , Zeaxantinas/metabolismo , Arabidopsis/genética , Arabidopsis/efeitos da radiação , Complexos de Proteínas Captadores de Luz/genética , Fotossíntese , Folhas de Planta/genética , Folhas de Planta/efeitos da radiação , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/efeitos da radiação , Tilacoides/metabolismo
18.
Proc Natl Acad Sci U S A ; 115(14): 3722-3727, 2018 04 03.
Artigo em Inglês | MEDLINE | ID: mdl-29555769

RESUMO

Photosynthetic organisms are frequently exposed to light intensities that surpass the photosynthetic electron transport capacity. Under these conditions, the excess absorbed energy can be transferred from excited chlorophyll in the triplet state (3Chl*) to molecular O2, which leads to the production of harmful reactive oxygen species. To avoid this photooxidative stress, photosynthetic organisms must respond to excess light. In the green alga Chlamydomonas reinhardtii, the fastest response to high light is nonphotochemical quenching, a process that allows safe dissipation of the excess energy as heat. The two proteins, UV-inducible LHCSR1 and blue light-inducible LHCSR3, appear to be responsible for this function. While the LHCSR3 protein has been intensively studied, the role of LHCSR1 has been only partially elucidated. To investigate the molecular functions of LHCSR1 in C. reinhardtii, we performed biochemical and spectroscopic experiments and found that the protein mediates excitation energy transfer from light-harvesting complexes for Photosystem II (LHCII) to Photosystem I (PSI), rather than Photosystem II, at a low pH. This altered excitation transfer allows remarkable fluorescence quenching under high light. Our findings suggest that there is a PSI-dependent photoprotection mechanism that is facilitated by LHCSR1.


Assuntos
Chlamydomonas reinhardtii/metabolismo , Fluorescência , Complexos de Proteínas Captadores de Luz/metabolismo , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Proteínas de Algas/química , Proteínas de Algas/genética , Proteínas de Algas/metabolismo , Chlamydomonas reinhardtii/efeitos da radiação , Transporte de Elétrons , Transferência de Energia , Concentração de Íons de Hidrogênio , Luz , Complexos de Proteínas Captadores de Luz/química , Complexos de Proteínas Captadores de Luz/genética , Fotossíntese , Complexo de Proteína do Fotossistema I/química , Complexo de Proteína do Fotossistema I/genética , Complexo de Proteína do Fotossistema II/química , Complexo de Proteína do Fotossistema II/genética , Tilacoides/química , Tilacoides/metabolismo
19.
PLoS One ; 13(3): e0194835, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29579114

RESUMO

Ascorbic acid (AsA), chlorophyll and carotenoid contents and their associated gene expression patterns were analysed in Actinidia chinensis 'Hongyang' outer pericarp. The results showed chlorophyll degradation during fruit development and softening, exposed the yellow carotenoid pigments. LHCB1 and CLS1 gene expressions were decreased, while PPH2 and PPH3 gene expressions were increased, indicating that downregulation of chlorophyll biosynthesis and upregulation of its degradation, caused chlorophyll degradation. A decrease in the expression of the late carotenoid biosynthesis and maintenance genes (LCYB1, LCYE1, CYP1, CYP2, ZEP1, VDE1, VDE2, and NCED2) and degradation gene (CCD1), showed biosynthesis and degradation of carotenoid could be regulatory factors involved in fruit development. Most genes expression data of L-galactose and recycling pathway were agreement with the AsA concentrations in the fruit, suggesting these are the predominant pathways of AsA biosynthesis. GMP1, GME1 and GGP1 were identified as the key genes controlling AsA biosynthesis in 'Hongyang' outer pericarp.


Assuntos
Actinidia/metabolismo , Ácido Ascórbico/metabolismo , Carotenoides/metabolismo , Clorofila/metabolismo , Actinidia/crescimento & desenvolvimento , Regulação para Baixo , Frutas/metabolismo , Complexos de Proteínas Captadores de Luz/genética , Complexos de Proteínas Captadores de Luz/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Regulação para Cima
20.
Photosynth Res ; 137(2): 161-169, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-29460034

RESUMO

Here we provide reflections of and a tribute to John M. Olson, a pioneering researcher in photosynthesis. We trace his career, which began at Wesleyan University and the University of Pennsylvania, and continued at Utrech in The Netherlands, Brookhaven National Laboratory, and Odense University in Denmark. He was the world expert on pigment organization in the green photosynthetic bacteria, and discovered and characterized the first chlorophyll-containing protein, which has come to be known as the Fenna-Matthews-Olson (FMO) protein. He also thought and wrote extensively on the origin and early evolution of photosynthesis. We include personal comments from Brian Matthews, Raymond Cox, Paolo Gerola, Beverly Pierson and Jon Olson.


Assuntos
Fotossíntese/fisiologia , Bactérias/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/história , Proteínas de Bactérias/metabolismo , Botânica/história , Dinamarca , História do Século XX , Complexos de Proteínas Captadores de Luz/genética , Complexos de Proteínas Captadores de Luz/história , Complexos de Proteínas Captadores de Luz/metabolismo , Estados Unidos
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