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1.
Int J Mol Sci ; 22(6)2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33804002

RESUMO

Antenna protein aggregation is one of the principal mechanisms considered effective in protecting phototrophs against high light damage. Commonly, it is induced, in vitro, by decreasing detergent concentration and pH of a solution of purified antennas; the resulting reduction in fluorescence emission is considered to be representative of non-photochemical quenching in vivo. However, little is known about the actual size and organization of antenna particles formed by this means, and hence the physiological relevance of this experimental approach is questionable. Here, a quasi-single molecule method, fluorescence correlation spectroscopy (FCS), was applied during in vitro quenching of LHCII trimers from higher plants for a parallel estimation of particle size, fluorescence, and antenna cluster homogeneity in a single measurement. FCS revealed that, below detergent critical micelle concentration, low pH promoted the formation of large protein oligomers of sizes up to micrometers, and therefore is apparently incompatible with thylakoid membranes. In contrast, LHCII clusters formed at high pH were smaller and homogenous, and yet still capable of efficient quenching. The results altogether set the physiological validity limits of in vitro quenching experiments. Our data also support the idea that the small, moderately quenching LHCII oligomers found at high pH could be relevant with respect to non-photochemical quenching in vivo.


Assuntos
Proteína do Homeodomínio de Antennapedia/genética , Complexos de Proteínas Captadores de Luz/genética , Processos Fototróficos/genética , Agregados Proteicos/genética , Proteína do Homeodomínio de Antennapedia/química , Clorofila/química , Clorofila/genética , Clorofila/efeitos da radiação , Análise por Conglomerados , Fluorescência , Concentração de Íons de Hidrogênio , Luz/efeitos adversos , Complexos de Proteínas Captadores de Luz/química , Fotossíntese/genética , Complexo de Proteína do Fotossistema II/genética , Complexo de Proteína do Fotossistema II/efeitos da radiação , Espectrometria de Fluorescência , Tilacoides/química , Tilacoides/genética , Tilacoides/efeitos da radiação , Zeaxantinas/genética
2.
BMC Plant Biol ; 21(1): 106, 2021 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-33610179

RESUMO

BACKGROUND: Photosystem II (PSII) is a highly conserved integral-membrane multi-subunit pigment-protein complex. The proteins, pigments, lipids, and ions in PSII need to be assembled precisely to ensure a proper PSII biogenesis. D1 is the main subunit of PSII core reaction center (RC), and is usually synthesized as a precursor D1. D1 maturation by the C-terminal processing protease CtpA is essential for PSII assembly. However, the detailed mechanism about how D1 maturation affects PSII assembly is not clearly elucidated so far. In this study, Arabidopsis thaliana CtpA mutant (atctpa: SALK_056011), which lacks the D1 mature process, was used to investigate the function of this process on PSII assembly in more details. RESULTS: Without the C-terminal processing of precursor D1, PSII assembly, including PSII monomer, dimer, especially PSII supercomplexes (PSII SCs), was largely compromised as reported previously. Western blotting following the BN-2D-SDS PAGE revealed that although the assembly of PSII core proteins D2, CP43 and CP47 was affected by the loss of D1 mature process, the incorporation of CP43 was affected the most, indicated by its most reduced assembly efficiency into PSII SCs. Furthermore, the slower growth of yeast cells which were co-transformed with pD1 and CP43, when compared with the ones co-transformed with mature D1 and CP43, approved the existence of D1 C-terminal tail hindered the interaction efficiency between D1 and CP43, indicating the physiological importance of D1 mature process on the PSII assembly and the healthy growth of the organisms. CONCLUSIONS: The knockout Arabidopsis atctpa mutant is a good material to study the unexpected link between D1 maturation and PSII SCs assembly. The loss of D1 maturation mainly affects the incorporation of PSII core protein CP43, an inner antenna binding protein, which functions in the association of LHCII complexes to PSII dimers during the formation of PSII SCs. Our findings here provide detailed supports of the role of D1 maturation during PSII SCs assembly in higher plants.


Assuntos
Arabidopsis/crescimento & desenvolvimento , Arabidopsis/genética , Complexos de Proteínas Captadores de Luz/genética , Complexos de Proteínas Captadores de Luz/metabolismo , Peptídeo Hidrolases/metabolismo , Fotossíntese/genética , Fotossíntese/fisiologia , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Peptídeo Hidrolases/genética
3.
Biochim Biophys Acta Bioenerg ; 1862(1): 148327, 2021 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-33069682

RESUMO

Iron-stress-induced-A proteins (IsiAs) are expressed in cyanobacteria under iron-deficient conditions, and surround photosystem I (PSI) trimer with a ring formation. A cyanobacterium Anabaena sp. PCC 7120 has four isiA genes; however, it is unknown how the IsiAs are associated with PSI. Here we report on molecular organizations and function of the IsiAs in this cyanobacterium. A deletion mutant of the isiA1 gene was constructed, and the four types of thylakoids were prepared from the wild-type (WT) and ΔisiA1 cells under iron-replete (+Fe) and iron-deficient (-Fe) conditions. Immunoblotting analysis exhibits a clear expression of the IsiA1 in the WT-Fe. The PSI-IsiA1 supercomplex is found in the WT-Fe, and excitation-energy transfer from IsiA1 to PSI is verified by time-resolved fluorescence analyses. Instead of the IsiA1, both IsiA2 and IsiA3 are bound to PSI monomer in the ΔisiA1-Fe. These findings provide insights into multiple-expression system of the IsiA family in this cyanobacterium.


Assuntos
Anabaena/enzimologia , Proteínas de Bactérias/metabolismo , Ferro/metabolismo , Complexos de Proteínas Captadores de Luz/metabolismo , Família Multigênica , Anabaena/genética , Proteínas de Bactérias/genética , Deleção de Genes , Regulação Bacteriana da Expressão Gênica , Complexos de Proteínas Captadores de Luz/genética
4.
Appl Environ Microbiol ; 86(13)2020 06 17.
Artigo em Inglês | MEDLINE | ID: mdl-32332138

RESUMO

Microorganisms in nature are commonly exposed to various stresses in parallel. The isiA gene encodes an iron stress-induced chlorophyll-binding protein which is significantly induced under iron starvation and oxidative stress. Acclimation of oxidative stress and iron deficiency was investigated using a regulatory mutant of the Synechocystis sp. strain PCC 6803. In this study, the ΔisiA mutant grew more slowly in oxidative-stress and iron depletion conditions compared to the wild-type (WT) counterpart under the same conditions. Thus, we performed transcriptome sequencing (RNA-seq) analysis of the WT strain and the ΔisiA mutant under double-stress conditions to obtain a comprehensive view of isiA-regulated genes. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses showed significant differences between the WT strain and ΔisiA mutant, mainly related to photosynthesis and the iron-sulfur cluster. The deletion of isiA affects the expression of various genes that are involved in cellular processes and structures, such as photosynthesis, phycobilisome, and the proton-transporting ATPase complex. Weighted gene coexpression network analysis (WGCNA) demonstrated three functional modules in which the turquoise module was negatively correlated with superoxide dismutase (SOD) activity. Coexpression network analysis identified several hub genes of each module. Cotranscriptional PCR and reads coverage using the Integrative Genomics Viewer demonstrated that isiA, isiB, isiC, ssl0461, and dfp belonged to the isi operon. Three sRNAs related to oxidative stress were identified. This study enriches our knowledge of IsiA-regulatory mechanisms under iron deficiency and oxidative stress.IMPORTANCE This study analyzed the impact of isiA deletion on the transcriptomic profile of Synechocystis The isiA gene encodes an iron stress-induced chlorophyll-binding protein, which is significantly induced under iron starvation. The deletion of isiA affects the expression of various genes that are involved in photosynthesis and ABC transporters. WGCNA revealed three functional modules in which the blue module was correlated with oxidative stress. We further demonstrated that the isi operon contained the following five genes: isiA, isiB, isiC, ssl0461, and dfp by cotranscriptional PCR. Three sRNAs were identified that were related to oxidative stress. This study enhances our knowledge of IsiA-regulatory mechanisms under iron deficiency and oxidative stress.


Assuntos
Proteínas de Bactérias/genética , Ferro/metabolismo , Complexos de Proteínas Captadores de Luz/genética , Estresse Oxidativo , Synechocystis/fisiologia , Aclimatação , Proteínas de Bactérias/metabolismo , Perfilação da Expressão Gênica , Complexos de Proteínas Captadores de Luz/metabolismo , Synechocystis/genética
5.
Sci Adv ; 6(10): eaaw9183, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32181334

RESUMO

Fucoxanthin and its derivatives are the main light-harvesting pigments in the photosynthetic apparatus of many chromalveolate algae and represent the most abundant carotenoids in the world's oceans, thus being major facilitators of marine primary production. A central step in fucoxanthin biosynthesis that has been elusive so far is the conversion of violaxanthin to neoxanthin. Here, we show that in chromalveolates, this reaction is catalyzed by violaxanthin de-epoxidase-like (VDL) proteins and that VDL is also involved in the formation of other light-harvesting carotenoids such as peridinin or vaucheriaxanthin. VDL is closely related to the photoprotective enzyme violaxanthin de-epoxidase that operates in plants and most algae, revealing that in major phyla of marine algae, an ancient gene duplication triggered the evolution of carotenoid functions beyond photoprotection toward light harvesting.


Assuntos
Proteínas de Algas/genética , Complexos de Proteínas Captadores de Luz/genética , Oxirredutases/genética , Feófitas/enzimologia , Xantofilas/metabolismo , Proteínas de Algas/metabolismo , Organismos Aquáticos , Carotenoides/metabolismo , Clorofila A/metabolismo , Regulação da Expressão Gênica , Complexos de Proteínas Captadores de Luz/metabolismo , Oxirredutases/metabolismo , Feófitas/classificação , Feófitas/genética , Filogenia
6.
Nat Commun ; 11(1): 1542, 2020 03 24.
Artigo em Inglês | MEDLINE | ID: mdl-32210238

RESUMO

Natural photosynthesis can be divided between the chlorophyll-containing plants, algae and cyanobacteria that make up the oxygenic phototrophs and a diversity of bacteriochlorophyll-containing bacteria that make up the anoxygenic phototrophs. Photosynthetic light harvesting and reaction centre proteins from both kingdoms have been exploited for solar energy conversion, solar fuel synthesis and sensing technologies, but the energy harvesting abilities of these devices are limited by each protein's individual palette of pigments. In this work we demonstrate a range of genetically-encoded, self-assembling photosystems in which recombinant plant light harvesting complexes are covalently locked with reaction centres from a purple photosynthetic bacterium, producing macromolecular chimeras that display mechanisms of polychromatic solar energy harvesting and conversion. Our findings illustrate the power of a synthetic biology approach in which bottom-up construction of photosystems using naturally diverse but mechanistically complementary components can be achieved in a predictable fashion through the encoding of adaptable, plug-and-play covalent interfaces.


Assuntos
Proteínas de Arabidopsis/química , Proteínas de Bactérias/química , Bacterioclorofilas/química , Complexos de Proteínas Captadores de Luz/química , Energia Solar , Biologia Sintética/métodos , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/efeitos da radiação , Proteínas de Bactérias/genética , Proteínas de Bactérias/efeitos da radiação , Bacterioclorofilas/genética , Bacterioclorofilas/efeitos da radiação , Carotenoides/química , Carotenoides/efeitos da radiação , Complexos de Proteínas Captadores de Luz/genética , Complexos de Proteínas Captadores de Luz/efeitos da radiação , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/efeitos da radiação , Rhodobacter sphaeroides/química , Rhodobacter sphaeroides/genética , Rhodobacter sphaeroides/efeitos da radiação , Luz Solar
7.
Sci Rep ; 10(1): 3376, 2020 02 25.
Artigo em Inglês | MEDLINE | ID: mdl-32099058

RESUMO

Dye-sensitized solar cells (DSSCs) have been highlighted as the promising alternative to generate clean energy based on low pay-back time materials. These devices have been designed to mimic solar energy conversion processes from photosynthetic organisms (the most efficient energy transduction phenomenon observed in nature) with the aid of low-cost materials. Recently, light-harvesting complexes (LHC) have been proposed as potential dyes in DSSCs based on their higher light-absorption efficiencies as compared to synthetic dyes. In this work, photo-electrochemical hybrid devices were rationally designed by adding for the first time Leu and Lys tags to heterologously expressed light-harvesting proteins from Chlamydomonas reinhardtii, thus allowing their proper orientation and immobilization on graphene electrodes. The light-harvesting complex 4 from C. reinhardtii (LHC4) was initially expressed in Escherichia coli, purified via affinity chromatography and subsequently immobilized on plasma-treated thin-film graphene electrodes. A photocurrent density of 40.30 ± 9.26 µA/cm2 was measured on devices using liquid electrolytes supplemented with a phosphonated viologen to facilitate charge transfer. Our results suggest that a new family of graphene-based thin-film photovoltaic devices can be manufactured from rationally tagged LHC proteins and opens the possibility to further explore fundamental processes of energy transfer for biological components interfaced with synthetic materials.


Assuntos
Proteínas de Algas/metabolismo , Chlamydomonas reinhardtii/metabolismo , Técnicas Eletroquímicas/métodos , Grafite/química , Complexos de Proteínas Captadores de Luz/metabolismo , Proteínas de Algas/genética , Corantes/química , Técnicas Eletroquímicas/instrumentação , Eletrodos , Proteínas Imobilizadas/química , Proteínas Imobilizadas/metabolismo , Complexos de Proteínas Captadores de Luz/genética , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/química , Proteínas Recombinantes/isolamento & purificação , Energia Solar
8.
Sci Rep ; 10(1): 2029, 2020 02 06.
Artigo em Inglês | MEDLINE | ID: mdl-32029835

RESUMO

Abiotic and biotic stresses widely reduce light harvesting complex (LHC) gene expression in higher plants and algae. However, control mechanisms and functions of these changes are not well understood. During herbivory, marine diatom species release oxylipins that impair grazer reproduction and serve as signaling molecules to nearby undamaged diatoms. To examine LHC mRNA regulation by oxylipin exposure, the diatom Phaeodactylum tricornutum was treated with a sublethal concentration of trans,trans-2,4-decadienal (DD) during the light cycle. Transcriptome analyses revealed extensive suppression of LHC mRNAs and a smaller set of up-regulated LHC mRNAs at 3 h. For two divergently regulated LHCF antennae family mRNAs, in vivo 4-thiouracil metabolic labeling was used to distinguish synthesis and degradation rates. Within 3 h of DD exposure, Lhcf2 mRNA levels and transcription were strongly suppressed and its mRNA half-life decreased. In contrast, Lhcf15 mRNA mainly accumulated between 3-9 h, its transcription increased and its mRNA was highly stabilized. Hence, DD-treated cells utilized transcriptional and mRNA stability control mechanisms which were likely major factors in the differing Lhcf2 and Lhcf15 expression patterns. Widespread LHC mRNA regulation and possible effects on photosynthesis may contribute to enhanced fitness in cells impacted by herbivory and other stresses.


Assuntos
Aldeídos/metabolismo , Diatomáceas/fisiologia , Complexos de Proteínas Captadores de Luz/genética , Fitoplâncton/fisiologia , Estresse Fisiológico/genética , Herbivoria , Estabilidade de RNA , RNA Mensageiro/metabolismo , Transcrição Genética/fisiologia , Regulação para Cima
9.
Nat Plants ; 6(2): 167-176, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-32042157

RESUMO

Under iron-deficiency stress, which occurs frequently in natural aquatic environments, cyanobacteria reduce the amount of iron-enriched proteins, including photosystem I (PSI) and ferredoxin (Fd), and upregulate the expression of iron-stress-induced proteins A and B (IsiA and flavodoxin (Fld)). Multiple IsiAs function as the peripheral antennae that encircle the PSI core, whereas Fld replaces Fd as the electron receptor of PSI. Here, we report the structures of the PSI3-IsiA18-Fld3 and PSI3-IsiA18 supercomplexes from Synechococcus sp. PCC 7942, revealing features that are different from the previously reported PSI structures, and a sophisticated pigment network that involves previously unobserved pigment molecules. Spectroscopic results demonstrated that IsiAs are efficient light harvesters for PSI. Three Flds bind symmetrically to the trimeric PSI core-we reveal the detailed interaction and the electron transport path between PSI and Fld. Our results provide a structural basis for understanding the mechanisms of light harvesting, energy transfer and electron transport of cyanobacterial PSI under stressed conditions.


Assuntos
Proteínas de Bactérias/genética , Transporte de Elétrons/genética , Metabolismo Energético , Flavodoxina/genética , Complexos de Proteínas Captadores de Luz/genética , Complexo de Proteína do Fotossistema I/genética , Synechococcus/fisiologia , Proteínas de Bactérias/metabolismo , Flavodoxina/metabolismo , Complexos de Proteínas Captadores de Luz/metabolismo , Complexo de Proteína do Fotossistema I/metabolismo , Synechococcus/genética
10.
J Biol Chem ; 295(7): 1857-1866, 2020 02 14.
Artigo em Inglês | MEDLINE | ID: mdl-31929108

RESUMO

Integral membrane proteins are exposed to a complex and dynamic lipid environment modulated by nonbilayer lipids that can influence protein functions by lipid-protein interactions. The nonbilayer lipid monogalactosyldiacylglycerol (MGDG) is the most abundant lipid in plant photosynthetic thylakoid membranes, but its impact on the functionality of energy-converting membrane protein complexes is unknown. Here, we optimized a detergent-based reconstitution protocol to develop a proteoliposome technique that incorporates the major light-harvesting complex II (LHCII) into compositionally well-defined large unilamellar lipid bilayer vesicles to study the impact of MGDG on light harvesting by LHCII. Using steady-state fluorescence spectroscopy, CD spectroscopy, and time-correlated single-photon counting, we found that both chlorophyll fluorescence quantum yields and fluorescence lifetimes clearly indicate that the presence of MGDG in lipid bilayers switches LHCII from a light-harvesting to a more energy-quenching mode that dissipates harvested light into heat. It is hypothesized that in the in vitro system developed here, MGDG controls light harvesting of LHCII by modulating the hydrostatic lateral membrane pressure profile in the lipid bilayer sensed by LHCII-bound peripheral pigments.


Assuntos
Galactolipídeos/química , Complexos de Proteínas Captadores de Luz/química , Fotossíntese/genética , Proteolipídeos/genética , Galactolipídeos/metabolismo , Complexos de Proteínas Captadores de Luz/genética , Metabolismo dos Lipídeos/genética , Proteínas Ligadas a Lipídeos/química , Proteínas Ligadas a Lipídeos/genética , Lipídeos/química , Lipídeos/genética , Proteínas de Membrana/química , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Proteínas Quinases/química , Proteínas Quinases/genética , Proteolipídeos/química , Proteolipídeos/metabolismo , Espectrometria de Fluorescência , Tilacoides/metabolismo
11.
Biochim Biophys Acta Bioenerg ; 1861(4): 148085, 2020 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-31672413

RESUMO

Two pale green mutants of the green alga Chlamydomonas reinhardtii, which have been used over the years in many photosynthesis studies, the BF4 and p71 mutants, were characterized and their mutated gene identified in the nuclear genome. The BF4 mutant is defective in the insertase Alb3.1 whereas p71 is defective in cpSRP43. The two mutants showed strikingly similar deficiencies in most of the peripheral antenna proteins associated with either photosystem I or photosystem 2. As a result the two photosystems have a reduced antenna size with photosystem 2 being the most affected. Still up to 20% of the antenna proteins remain in these strains, with the heterodimer Lhca5/Lhca6 showing a lower sensitivity to these mutations. We discuss these phenotypes in light of those of other allelic mutants that have been described in the literature and suggest that eventhough the cpSRP route serves as the main biogenesis pathway for antenna proteins, there should be an escape pathway which remains to be genetically identified.


Assuntos
Chlamydomonas reinhardtii/genética , Complexos de Proteínas Captadores de Luz/genética , Mutação/genética , Clorofila/metabolismo , Complexos de Proteínas Captadores de Luz/metabolismo , Fenótipo , Fosforilação , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Espectrometria de Fluorescência , Temperatura
12.
J Biol Chem ; 295(51): 17816-17826, 2020 12 18.
Artigo em Inglês | MEDLINE | ID: mdl-33454016

RESUMO

Nonphotochemical quenching (NPQ) is a mechanism of regulating light harvesting that protects the photosynthetic apparatus from photodamage by dissipating excess absorbed excitation energy as heat. In higher plants, the major light-harvesting antenna complex (LHCII) of photosystem (PS) II is directly involved in NPQ. The aggregation of LHCII is proposed to be involved in quenching. However, the lack of success in isolating native LHCII aggregates has limited the direct interrogation of this process. The isolation of LHCII in its native state from thylakoid membranes has been problematic because of the use of detergent, which tends to dissociate loosely bound proteins, and the abundance of pigment-protein complexes (e.g. PSI and PSII) embedded in the photosynthetic membrane, which hinders the preparation of aggregated LHCII. Here, we used a novel purification method employing detergent and amphipols to entrap LHCII in its natural states. To enrich the photosynthetic membrane with the major LHCII, we used Arabidopsis thaliana plants lacking the PSII minor antenna complexes (NoM), treated with lincomycin to inhibit the synthesis of PSI and PSII core proteins. Using sucrose density gradients, we succeeded in isolating the trimeric and aggregated forms of LHCII antenna. Violaxanthin- and zeaxanthin-enriched complexes were investigated in dark-adapted, NPQ, and dark recovery states. Zeaxanthin-enriched antenna complexes showed the greatest amount of aggregated LHCII. Notably, the amount of aggregated LHCII decreased upon relaxation of NPQ. Employing this novel preparative method, we obtained a direct evidence for the role of in vivo LHCII aggregation in NPQ.


Assuntos
Arabidopsis/metabolismo , Complexos de Proteínas Captadores de Luz/metabolismo , Tilacoides/metabolismo , Arabidopsis/efeitos dos fármacos , Cinética , Complexos de Proteínas Captadores de Luz/química , Complexos de Proteínas Captadores de Luz/genética , Complexos de Proteínas Captadores de Luz/isolamento & purificação , Lincomicina/farmacologia , Plantas Geneticamente Modificadas/efeitos dos fármacos , Plantas Geneticamente Modificadas/metabolismo , Multimerização Proteica , Espectrometria de Fluorescência , Ultracentrifugação , Xantofilas/química , Xantofilas/metabolismo , Zeaxantinas/química , Zeaxantinas/metabolismo
13.
Nat Plants ; 5(12): 1320-1330, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31768031

RESUMO

Green algae and plants rely on light-harvesting complex II (LHCII) to collect photon energy for oxygenic photosynthesis. In Chlamydomonas reinhardtii, LHCII molecules associate with photosystem II (PSII) to form various supercomplexes, including the C2S2M2L2 type, which is the largest PSII-LHCII supercomplex in algae and plants that is presently known. Here, we report high-resolution cryo-electron microscopy (cryo-EM) maps and structural models of the C2S2M2L2 and C2S2 supercomplexes from C. reinhardtii. The C2S2 supercomplex contains an LhcbM1-LhcbM2/7-LhcbM3 heterotrimer in the strongly associated LHCII, and the LhcbM1 subunit assembles with CP43 through two interfacial galactolipid molecules. The loosely and moderately associated LHCII trimers interact closely with the minor antenna complex CP29 to form an intricate subcomplex bound to CP47 in the C2S2M2L2 supercomplex. A notable direct pathway is established for energy transfer from the loosely associated LHCII to the PSII reaction centre, as well as several indirect routes. Structure-based computational analysis on the excitation energy transfer within the two supercomplexes provides detailed mechanistic insights into the light-harvesting process in green algae.


Assuntos
Chlamydomonas reinhardtii/metabolismo , Complexo de Proteína do Fotossistema II/química , Proteínas de Plantas/química , Chlamydomonas reinhardtii/química , Chlamydomonas reinhardtii/genética , Chlamydomonas reinhardtii/efeitos da radiação , Clorofila/metabolismo , Microscopia Crioeletrônica , Transferência de Energia , Luz , Complexos de Proteínas Captadores de Luz/genética , Complexos de Proteínas Captadores de Luz/metabolismo , Modelos Moleculares , Fotossíntese , Complexo de Proteína do Fotossistema II/genética , Complexo de Proteína do Fotossistema II/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Ligação Proteica
14.
mBio ; 10(6)2019 11 26.
Artigo em Inglês | MEDLINE | ID: mdl-31772049

RESUMO

The purple nonsulfur bacterium Rhodopseudomonas palustris is a model for understanding how a phototrophic organism adapts to changes in light intensity because it produces different light-harvesting (LH) complexes under high light (LH2) and low light intensities (LH3 and LH4). Outside of this change in the composition of the photosystem, little is understood about how R. palustris senses and responds to low light intensity. On the basis of the results of transcription analysis of 17 R. palustris strains grown in low light, we found that R. palustris strains downregulate many genes involved in iron transport and homeostasis. The only operon upregulated in the majority of R. palustris exposed to low light intensity was pucBAd, which encodes LH4. In previous work, pucBAd expression was shown to be modulated in response to light quality by bacteriophytochromes that are part of a low-light signal transduction system. Here we found that this signal transduction system also includes a redox-sensitive protein, LhfE, and that its redox sensitivity is required for LH4 synthesis in response to low light. Our results suggest that R. palustris upregulates its LH4 system when the cellular redox state is relatively oxidized. Consistent with this, we found that LH4 synthesis was upregulated under high light intensity when R. palustris was grown semiaerobically or under nitrogen-fixing conditions. Thus, changes in the LH4 system in R. palustris are not dependent on light intensity per se but rather on cellular redox changes that occur as a consequence of changes in light intensity.IMPORTANCE An essential aspect of the physiology of phototrophic bacteria is their ability to adjust the amount and composition of their light-harvesting apparatus in response to changing environmental conditions. The phototrophic purple bacterium R. palustris adapts its photosystem to a range of light intensities by altering the amount and composition of its peripheral LH complexes. Here we found that R. palustris regulates its LH4 complex in response to the cellular redox state rather than in response to light intensity per se Relatively oxidizing conditions, including low light, semiaerobic growth, and growth under nitrogen-fixing conditions, all stimulated a signal transduction system to activate LH4 expression. By understanding how LH composition is regulated in R. palustris, we will gain insight into how and why a photosynthetic organism senses and adapts its photosystem to multiple environmental cues.


Assuntos
Oxigênio/metabolismo , Rodopseudomonas/metabolismo , Rodopseudomonas/efeitos da radiação , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Regulação Bacteriana da Expressão Gênica/efeitos da radiação , Luz , Complexos de Proteínas Captadores de Luz/genética , Complexos de Proteínas Captadores de Luz/metabolismo , Óperon , Oxirredução , Fotossíntese , Rodopseudomonas/genética
16.
J Plant Res ; 132(6): 867-880, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31541373

RESUMO

Mosses are one of the earliest land plants that diverged from fresh-water green algae. They are considered to have acquired a higher capacity for thermal energy dissipation to cope with dynamically changing solar irradiance by utilizing both the "algal-type" light-harvesting complex stress-related (LHCSR)-dependent and the "plant-type" PsbS-dependent mechanisms. It is hypothesized that the formation of photosystem (PS) I and II megacomplex is another mechanism to protect photosynthetic machinery from strong irradiance. Herein, we describe the analysis of the PSI-PSII megacomplex from the model moss, Physcomitrella patens, which was resolved using large-pore clear-native polyacrylamide gel electrophoresis (lpCN-PAGE). The similarity in the migration distance of the Physcomitrella PSI-PSII megacomplex to the Arabidopsis megacomplex shown during lpCN-PAGE suggested that the Physcomitrella PSI-PSII and Arabidopsis megacomplexes have similar structures. Time-resolved chlorophyll fluorescence measurements show that excitation energy was rapidly and efficiently transferred from PSII to PSI, providing evidence of an ordered association of the two photosystems. We also found that LHCSR and PsbS co-migrated with the Physcomitrella PSI-PSII megacomplex. The megacomplex showed pH-dependent chlorophyll fluorescence quenching, which may have been induced by LHCSR and/or PsbS proteins with the collaboration of zeaxanthin. We discuss the mechanism that regulates the energy distribution balance between two photosystems in Physcomitrella.


Assuntos
Bryopsida/genética , Complexos de Proteínas Captadores de Luz/genética , Complexo de Proteína do Fotossistema I/genética , Complexo de Proteína do Fotossistema II/genética , Proteínas de Plantas/genética , Bryopsida/enzimologia , Eletroforese em Gel de Poliacrilamida , Complexos de Proteínas Captadores de Luz/metabolismo , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Proteínas de Plantas/metabolismo
17.
FEBS Lett ; 593(22): 3190-3197, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31444795

RESUMO

In higher plants, PsbS is known to play a key role in the regulation of photosynthetic light harvesting. However, the molecular mechanism and role of electronic carotenoid-chlorophyll (Chl) interactions for the downregulation of excess excitation (nonphotochemical energy quenching, NPQ) are still poorly understood. Here, we explored carotenoid â†’ Chl energy transfer in isolated grana thylakoid membranes from mutants either deficient in or overexpressing PsbS. Since it was suggested that PsbS regulates the supramolecular protein network to control NPQ, we varied this network by diluting the grana protein densities. Our results indicate that different electronic quenching mechanisms are operative in grana thylakoids: a PsbS-dependent mechanism and a membrane protein density-dependent mechanism that is also operative in the absence of PsbS.


Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/metabolismo , Carotenoides/metabolismo , Clorofila/metabolismo , Complexos de Proteínas Captadores de Luz/genética , Complexo de Proteína do Fotossistema II/genética , Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Transferência de Energia , Complexos de Proteínas Captadores de Luz/metabolismo , Mutação , Complexo de Proteína do Fotossistema II/metabolismo , Tilacoides/metabolismo , Regulação para Cima
18.
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
19.
Photosynth Res ; 142(3): 249-264, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31270669

RESUMO

Non-photochemical quenching, NPQ, of chlorophyll fluorescence regulates the heat dissipation of chlorophyll excited states and determines the efficiency of the oxygenic photosynthetic systems. NPQ is regulated by a pH-sensing protein, responding to the chloroplast lumen acidification induced by excess light, coupled to an actuator, a chlorophyll/xanthophyll subunit where quenching reactions are catalyzed. In plants, the sensor is PSBS, while the two pigment-binding proteins Lhcb4 (also known as CP29) and LHCII are the actuators. In algae and mosses, stress-related light-harvesting proteins (LHCSR) comprise both functions of sensor and actuator within a single subunit. Here, we report on expressing the lhcsr1 gene from the moss Physcomitrella patens into several Arabidopsis thaliana npq4 mutants lacking the pH sensing PSBS protein essential for NPQ activity. The heterologous protein LHCSR1 accumulates in thylakoids of A. thaliana and NPQ activity can be partially restored. Complementation of double mutants lacking, besides PSBS, specific xanthophylls, allowed analyzing chromophore requirement for LHCSR-dependent quenching activity. We show that the partial recovery of NPQ is mostly due to the lower levels of Zeaxanthin in A. thaliana in comparison to P. patens. Complemented npq2npq4 mutants, lacking besides PSBS, Zeaxanthin Epoxidase, showed an NPQ recovery of up to 70% in comparison to A. thaliana wild type. Furthermore, we show that Lutein is not essential for the folding nor for the quenching activity of LHCSR1. In short, we have developed a system to study the function of LHCSR proteins using heterologous expression in a variety of A. thaliana mutants.


Assuntos
Arabidopsis/metabolismo , Bryopsida/genética , Complexos de Proteínas Captadores de Luz/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Arabidopsis/genética , Regulação da Expressão Gênica de Plantas , Luz , Complexos de Proteínas Captadores de Luz/genética , Mutação , Oxirredutases/genética , Oxirredutases/metabolismo , Processos Fotoquímicos , Fotossíntese , Plantas Geneticamente Modificadas , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Tilacoides/genética , Tilacoides/metabolismo , Xantofilas/metabolismo , Zeaxantinas/metabolismo
20.
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
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