Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 781
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Nat Commun ; 10(1): 4099, 2019 09 10.
Artigo em Inglês | MEDLINE | ID: mdl-31506429

RESUMO

Light is essential for photosynthesis, but the amounts of light that exceed an organism's assimilation capacity can result in oxidative stress and even cell death. Plants and microalgae have developed a photoprotective response mechanism, qE, that dissipates excess light energy as thermal energy. In the green alga Chlamydomonas reinhardtii, qE is regulated by light-inducible photoprotective proteins, but the pathway from light perception to qE is not fully understood. Here, we show that the transcription factors CONSTANS and Nuclear transcription Factor Ys (NF-Ys) form a complex that governs light-dependent photoprotective responses in C. reinhardtii. The qE responses do not occur in CONSTANS or NF-Y mutants. The signal from light perception to the CONSTANS/NF-Ys complex is directly inhibited by the SPA1/COP1-dependent E3 ubiquitin ligase. This negative regulation mediated by the E3 ubiquitin ligase and the CONSTANS/NF-Ys complex is common to photoprotective response in algal photosynthesis and flowering in plants.


Assuntos
Proteínas de Algas/metabolismo , Chlamydomonas/metabolismo , Fotossíntese , Regiões Promotoras Genéticas/genética , Ligação Proteica , Transdução de Sinais , Transcrição Genética , Ubiquitina-Proteína Ligases/metabolismo
2.
Mol Biol Cell ; 30(15): 1834-1845, 2019 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-31116681

RESUMO

WDR92 associates with a prefoldin-like cochaperone complex and known dynein assembly factors. WDR92 has been very highly conserved and has a phylogenetic signature consistent with it playing a role in motile ciliary assembly or activity. Knockdown of WDR92 expression in planaria resulted in ciliary loss, reduced beat frequency and dyskinetic motion of the remaining ventral cilia. We have now identified a Chlamydomonas wdr92 mutant that encodes a protein missing the last four WD repeats. The wdr92-1 mutant builds only ∼0.7-µm cilia lacking both inner and outer dynein arms, but with intact doublet microtubules and central pair. When cytoplasmic extracts prepared by freeze/thaw from a control strain were fractionated by gel filtration, outer arm dynein components were present in several distinct high molecular weight complexes. In contrast, wdr92-1 extracts almost completely lacked all three outer arm heavy chains, while the IFT dynein heavy chain was present in normal amounts. A wdr92-1 tpg1-2 double mutant builds ∼7-µm immotile flaccid cilia that completely lack dynein arms. These data indicate that WDR92 is a key assembly factor specifically required for the stability of axonemal dynein heavy chains in cytoplasm and suggest that cytoplasmic/IFT dynein heavy chains use a distinct folding pathway.


Assuntos
Proteínas de Algas/metabolismo , Axonema/metabolismo , Chlamydomonas/metabolismo , Dineínas/metabolismo , Repetições WD40 , Proteínas de Algas/química , Sequência de Aminoácidos , Axonema/ultraestrutura , Sequência de Bases , Chlamydomonas/ultraestrutura , Cílios/metabolismo , Cílios/ultraestrutura , Ritmo Circadiano , Ácido Glutâmico/metabolismo , Modelos Biológicos , Mutação/genética , Estabilidade Proteica
3.
Nat Commun ; 10(1): 1993, 2019 04 30.
Artigo em Inglês | MEDLINE | ID: mdl-31040285

RESUMO

Microbial rhodopsins are photoreceptive membrane proteins that transport various ions using light energy. While they are widely used in optogenetics to optically control neuronal activity, rhodopsins that function with longer-wavelength light are highly demanded because of their low phototoxicity and high tissue penetration. Here, we achieve a 40-nm red-shift in the absorption wavelength of a sodium-pump rhodopsin (KR2) by altering dipole moment of residues around the retinal chromophore (KR2 P219T/S254A) without impairing its ion-transport activity. Structural differences in the chromophore of the red-shifted protein from that of the wildtype are observed by Fourier transform infrared spectroscopy. QM/MM models generated with an automated protocol show that the changes in the electrostatic interaction between protein and chromophore induced by the amino-acid replacements, lowered the energy gap between the ground and the first electronically excited state. Based on these insights, a natural sodium pump with red-shifted absorption is identified from Jannaschia seosinensis.


Assuntos
Luz , Rodopsina/genética , ATPase Trocadora de Sódio-Potássio/genética , Chlamydomonas/metabolismo , Humanos , Mutação/genética , Teoria Quântica , Espectroscopia de Infravermelho com Transformada de Fourier , Eletricidade Estática
4.
Lipids ; 54(4): 255-262, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-31025716

RESUMO

Eukaryotic microalgae have been known for high competency in the accumulation of triacylglycerol (TAG), a representative class of storage lipid. The snow algal species, Chlamydomonas nivalis, is a unique green eukaryotic microalga that can grow and survive in a wide range of temperatures. Although a few metabolomic studies of C. nivalis were conducted, no study has reported on TAG accumulation in C. nivalis. Herein, the present work aimed to investigate TAG production in C. nivalis under nutrient-starved conditions at 22 °C. Compared to phosphorus starvation, C. nivalis under nitrogen starvation showed a less severe growth defect, greater capacity for TAG production, and simple acyl composition in TAG enriched with 18:1. These features suggest that C. nivalis may be a significant model species to investigate glycerolipid metabolism for basic and applied research.


Assuntos
Chlamydomonas/metabolismo , Triglicerídeos/metabolismo , Temperatura Ambiente
5.
Cell Mol Life Sci ; 76(12): 2329-2348, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30879092

RESUMO

Many secreted peptides used for cell-cell communication require conversion of a C-terminal glycine to an amide for bioactivity. This reaction is catalyzed only by the integral membrane protein peptidylglycine α-amidating monooxygenase (PAM). PAM has been highly conserved and is found throughout the metazoa; PAM-like sequences are also present in choanoflagellates, filastereans, unicellular and colonial chlorophyte green algae, dinoflagellates and haptophytes. Recent studies have revealed that in addition to playing a key role in peptidergic signaling, PAM also regulates ciliogenesis in vertebrates, planaria and chlorophyte algae, and is required for the stability of actin-based microvilli. Here we briefly introduce the basic principles involved in ciliogenesis, the sequential reactions catalyzed by PAM and the trafficking of PAM through the secretory and endocytic pathways. We then discuss the multi-faceted roles this enzyme plays in the formation and maintenance of cytoskeleton-based cellular protrusions and propose models for how PAM protein and amidating activity might contribute to ciliogenesis. Finally, we consider why some ciliated organisms lack PAM, and discuss the potential ramifications of ciliary localized PAM for the endocrine features commonly observed in patients with ciliopathies.


Assuntos
Chlamydomonas/enzimologia , Cílios/metabolismo , Oxigenases de Função Mista/metabolismo , Complexos Multienzimáticos/metabolismo , Peptídeos/metabolismo , Proteínas de Plantas/metabolismo , Actinas/metabolismo , Chlamydomonas/citologia , Chlamydomonas/metabolismo , Chlamydomonas/ultraestrutura , Cílios/ultraestrutura , Oxigenases de Função Mista/análise , Modelos Moleculares , Complexos Multienzimáticos/análise , Proteínas de Plantas/análise , Biossíntese de Proteínas , Transporte Proteico , Transdução de Sinais
6.
Physiol Plant ; 166(1): 451-459, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30809817

RESUMO

Pentatricopeptide repeat (PPR) proteins are important RNA regulators in chloroplasts and mitochondria, aiding in RNA editing, maturation, stabilisation or intron splicing, and in transcription and translation of organellar genes. In this review, we summarise all PPR proteins documented so far in plants and the green alga Chlamydomonas. By further analysis of the known target RNAs from Arabidopsis thaliana PPR proteins, we find that all organellar-encoded complexes are regulated by these proteins, although to differing extents. In particular, the orthologous complexes of NADH dehydrogenase (Complex I) in the mitochondria and NADH dehydrogenase-like (NDH) complex in the chloroplast were the most regulated, with respectively 60 and 28% of all characterised A. thaliana PPR proteins targeting their genes.


Assuntos
Chlamydomonas/metabolismo , Proteínas de Plantas/metabolismo , Proteínas de Arabidopsis/metabolismo , Cloroplastos/metabolismo , NADH Desidrogenase/metabolismo , Edição de RNA/genética
7.
Bioresour Technol ; 275: 416-420, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30626542

RESUMO

The marine microalga Chlamydomonas sp. JSC4 is a potential lutein source with high light tolerance. In this study, light intensity was manipulated to enhance cell growth and lutein production of this microalga. High lutein productivity (5.08 mg/L/d) was achieved under high light irradiation of 625 µmol/m2/s. Further increase in light intensity to 750 µmol/m2/s enhanced the biomass productivity to 1821.5 mg/L/d, but led to a decrease in lutein content. Under high light conditions, most carotenoids and chlorophyll contents decreased, while zeaxanthin and antheraxanthin contents increased. Inspection of gene expression profile shows that the lut1 and zep genes, responsible for lutein synthesis and flow of zeaxanthin into violaxanthin, respectively, were downregulated, while zeaxanthin biosynthesis gene crtZ was upregulated when the microalga was exposed to a high light intensity. This is consistent with the decrease in lutein content and increase in zeaxanthin content under high light exposure.


Assuntos
Chlamydomonas/metabolismo , Luteína/biossíntese , Biomassa , Chlamydomonas/genética , Clorofila/metabolismo , Luz , Transcriptoma , Xantofilas/biossíntese , Zeaxantinas/biossíntese
8.
Plant Cell Physiol ; 60(4): 916-930, 2019 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-30668822

RESUMO

Nutrient-deprived microalgae accumulate triacylglycerol (TAG) in lipid droplets. A dual-specificity tyrosine phosphorylation-regulated kinase, TAG accumulation regulator 1 (TAR1) has been shown to be required for acetate-dependent TAG accumulation and the degradation of chlorophyll and photosynthesis-related proteins in photomixotrophic nitrogen (N)-deficient conditions (Kajikawa et�al. 2015). However, this previous report only examined particular condition. Here, we report that in photoautotrophic N-deficient conditions, tar1-1 cells, with a mutation in the TAR1 gene, maintained higher levels of cell viability and lower levels of hydrogen peroxide generation and accumulated higher levels of TAG and starch compared with those of wild type (WT) cells with bubbling of air containing 5% carbon dioxide. Transcriptomic analyses suggested that genes involved in the scavenging of reactive oxygen species are not repressed in tar1-1 cells. In contrast, the mating efficiency and mRNA levels of key regulatory genes for gametogenesis, MID, MTD and FUS, were suppressed in tar1-1 cells. Among the TAR1-dependent phosphopeptides deduced by phosphoproteomic analysis, protein kinases and enzymes related to N assimilation and carbon (C) metabolism are of particular interest. Characterization of these putative downstream factors may elucidate the molecular pathway whereby TAR1 mediates cellular propagation and C and N metabolism in C/N-imbalanced stress conditions.


Assuntos
Chlamydomonas reinhardtii/metabolismo , Chlamydomonas/metabolismo , Triglicerídeos/metabolismo , Carbono/metabolismo , Sobrevivência Celular/genética , Sobrevivência Celular/fisiologia , Peróxido de Hidrogênio/metabolismo , Nitrogênio/metabolismo , Proteínas Quinases/metabolismo
9.
Proc Natl Acad Sci U S A ; 116(6): 2374-2383, 2019 02 05.
Artigo em Inglês | MEDLINE | ID: mdl-30659148

RESUMO

The unicellular green alga Chlamydomonas reinhardtii displays metabolic flexibility in response to a changing environment. We analyzed expression patterns of its three genomes in cells grown under light-dark cycles. Nearly 85% of transcribed genes show differential expression, with different sets of transcripts being up-regulated over the course of the day to coordinate cellular growth before undergoing cell division. Parallel measurements of select metabolites and pigments, physiological parameters, and a subset of proteins allow us to infer metabolic events and to evaluate the impact of the transcriptome on the proteome. Among the findings are the observations that Chlamydomonas exhibits lower respiratory activity at night compared with the day; multiple fermentation pathways, some oxygen-sensitive, are expressed at night in aerated cultures; we propose that the ferredoxin, FDX9, is potentially the electron donor to hydrogenases. The light stress-responsive genes PSBS, LHCSR1, and LHCSR3 show an acute response to lights-on at dawn under abrupt dark-to-light transitions, while LHCSR3 genes also exhibit a later, second burst in expression in the middle of the day dependent on light intensity. Each response to light (acute and sustained) can be selectively activated under specific conditions. Our expression dataset, complemented with coexpression networks and metabolite profiling, should constitute an excellent resource for the algal and plant communities.


Assuntos
Chlamydomonas/genética , Chlamydomonas/metabolismo , Genômica , Metabolômica , Proteômica , Divisão Celular , Replicação do DNA , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Genômica/métodos , Glicólise , Metaboloma , Metabolômica/métodos , NAD/metabolismo , Oxirredução , Fotossíntese/genética , Proteoma , Proteômica/métodos , Transdução de Sinais , Transcriptoma
10.
Bioresour Technol ; 272: 281-287, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30366287

RESUMO

An integrated production of methyl ester and ɛ-polylysine from Chlamydomonas sp. was studied using biorefinery approach. The harvesting efficiency of Chlamydomonas sp. was increased up to 92% by treatment with a flocculant FeCl3 at 100 mg/L for 30 min. The DMC (dimethyl carbonate) mediated enzyme catalyzed in-situ transesterification of Chlamydomonas sp. yielded the maximum methyl ester of 92% under optimized conditions. The valued-added product ɛ-polylysine was produced from hydrolysate obtained from the spent biomass of Chlamydomonas sp. using Streptomyces sp. The key components of sugar and MgSO4 used for ɛ-polysine production were optimized whereby the maximum ɛ-polylysine production was achieved at 50 g/L sugar and 0.3 g/L MgSO4. The ɛ-polylysine production was further enhanced by supplementation of important amino acids (lysine and aspartate) and TCA cycle intermediates (citric acid and α-ketoglutaric acid). The maximum ɛ-polylysine production of 2.24 g/L was found with 4 mM citric acid supplementation after 110 h.


Assuntos
Chlamydomonas/metabolismo , Ésteres/metabolismo , Polilisina/biossíntese , Biomassa , Esterificação , Metilação
11.
Plant Cell Physiol ; 60(1): 126-138, 2019 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-30295899

RESUMO

Autophagy is a recycling system for amino acids and carbon- and nitrogen (N)-containing compounds. To date, the functional importance of autophagy in microalgae in nutrient-deficient conditions has not been evaluated by using autophagy-defective mutants. Here, we provide evidence which supports the following notions by characterizing an insertional mutant of the autophagy-related gene ATG8, encoding a ubiquitin-like protein necessary for the formation of the autophagosome in the green alga, Chlamydomonas reinhardtii. First, ATG8 is required for maintenance of cell survival and Chl content in N-, sulfur- and phosphate-deficient conditions. Secondly, ATG8 supports the degradation of triacylglycerol and lipid droplets after the resupply of N to cells cultured in N-limiting conditions. Thirdly, ATG8 is also necessary for accumulation of starch in phosphate-deficient conditions. Additionally, autophagy is not essential for maternal inheritance of the organelle genomes in gametogenesis.


Assuntos
Autofagia , Chlamydomonas/genética , Mutação/genética , Nitrogênio/deficiência , Fosfatos/deficiência , Enxofre/deficiência , Proteínas Relacionadas à Autofagia/metabolismo , Carbono/metabolismo , Sobrevivência Celular , Chlamydomonas/metabolismo , Clorofila/metabolismo , Lipídeos/química , Fenótipo , Ubiquitina/metabolismo
12.
Appl Biochem Biotechnol ; 188(2): 326-337, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30443891

RESUMO

A lipid-producing microalga, Chlamydomonas sp. KNF0008, collected from the Arctic was capable of growing at temperatures ranging from 4 to 20 °C, and the highest cell density was measured at 15 °C and 100 µmol photons m-2 s-1 light intensity under continuous shaking and external aeration. KNF0008 showed the elevated accumulation of lipid bodies under nitrogen-deficient conditions, rather than under nitrogen-sufficient conditions. Fatty acid production of KNF0008 was 4.2-fold (104 mg L-1) higher than that of C. reinhardtii CC-125 at 15 °C in Bold's Basal Medium. The dominant fatty acids were C16:0, C16:4, C18:1, and C18:3, and unsaturated fatty acids (65.69%) were higher than saturated fatty acids (13.65%) at 15 °C. These results suggested that Arctic Chlamydomonas sp. KNF0008 could possibly be utilized for production of biodiesel during periods of cold weather because of its psychrophilic characteristics.


Assuntos
Chlamydomonas/metabolismo , Lipídeos/biossíntese , Microalgas/metabolismo , Regiões Árticas , Biocombustíveis , Chlamydomonas/classificação , Chlamydomonas/genética , Temperatura Baixa , Ácidos Graxos/biossíntese , Ácidos Graxos/química , Cinética , Luz , Lipídeos/química , Microalgas/classificação , Microalgas/genética , Nitrogênio/metabolismo , Filogenia
13.
BMC Plant Biol ; 18(1): 305, 2018 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-30482162

RESUMO

BACKGROUND: The PII proteins constitute a large superfamily, present in all domains of life. Until now, PII proteins research in Chloroplastida (green algae and land plants) has mainly focused on post-translation regulation of these signal transductors. Emerging evidence suggests that PII level is tightly controlled with regard to the nitrogen source and the physiological state of cells. RESULT: Here we identify that a balance of positive (nitrate and nitrite) and negative (nitric oxide) signals regulates Chlamydomonas GLB1. We found that PII expression is downregulated by ammonium through a nitric oxide (NO)-dependent mechanism. We show that nitrate reductase (NR) and its partner, truncated hemoglobin 1 (THB1), participate in a signaling pathway for dual control of GLB1 expression. Moreover, NO dependent guanilate cyclase appeared to be involved in the negative control of GLB1 transcription. CONCLUSION: This study has revealed the existence of the complex GLB1 control at transcription level, which is dependent on nitrogen source. Importantly, we found that GLB1 gene expression pattern is very similar to that observed for nitrate assimilation genes, suggesting interconnecting/coordinating PII-dependent and nitrate assimilation pathways.


Assuntos
Chlamydomonas/metabolismo , Nitratos/metabolismo , Óxido Nítrico/metabolismo , Nitritos/metabolismo , Proteínas PII Reguladoras de Nitrogênio/metabolismo , Chlamydomonas/genética , Regulação da Expressão Gênica , Redes e Vias Metabólicas , Transcrição Genética
14.
Nat Commun ; 9(1): 4650, 2018 11 07.
Artigo em Inglês | MEDLINE | ID: mdl-30405128

RESUMO

Resource limitation is a major driver of the ecological and evolutionary dynamics of organisms. Short-term responses to resource limitation include plastic changes in molecular phenotypes including protein expression. Yet little is known about the evolution of the molecular phenotype under longer-term resource limitation. Here, we combine experimental evolution of the green alga Chlamydomonas reinhardtii under multiple different non-substitutable resource limitation regimes with proteomic measurements to investigate evolutionary adaptation of the molecular phenotype. We demonstrate convergent proteomic evolution of core metabolic functions, including the Calvin-Benson cycle and gluconeogenesis, across different resource limitation environments. We do not observe proteomic changes consistent with optimized uptake of particular limiting resources. Instead, we report that adaptation proceeds in similar directions under different types of non-substitutable resource limitation. This largely convergent evolution of the expression of core metabolic proteins is associated with an improvement in the resource assimilation efficiency of nitrogen and phosphorus into biomass.


Assuntos
Evolução Molecular Direcionada , Proteoma/metabolismo , Proteínas de Algas/metabolismo , Chlamydomonas/efeitos dos fármacos , Chlamydomonas/metabolismo , Cromossomos/metabolismo , Redes e Vias Metabólicas/efeitos dos fármacos , Anotação de Sequência Molecular , Peptídeos/metabolismo , Cloreto de Sódio/farmacologia , Estresse Fisiológico/efeitos dos fármacos , Fatores de Tempo
15.
PLoS Biol ; 16(8): e2006357, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-30102690

RESUMO

HAPLESS2 (HAP2) is a broadly conserved, gamete-expressed transmembrane protein that was shown recently to be structurally homologous to viral class II fusion proteins, which initiate fusion with host cells via insertion of fusion loops into the host membrane. However, the functional conformation of the HAP2 fusion loops has remained unknown, as the reported X-ray structure of Chlamydomonas reinhardtii HAP2 lacked this critical region. Here, we report a structure-guided alignment that reveals diversification of the proposed HAP2 fusion loops. Representative crystal structures show that in flowering plants, HAP2 has a single prominent fusion loop projecting an amphipathic helix at its apex, while in trypanosomes, three small nonpolar loops of HAP2 are poised to interact with the target membrane. A detailed structure-function analysis of the Arabidopsis HAP2 amphipathic fusion helix defines key residues that are essential for membrane insertion and for gamete fusion. Our study suggests that HAP2 may have evolved multiple modes of membrane insertion to accommodate the diversity of membrane environments it has encountered during eukaryotic evolution.


Assuntos
Proteínas de Arabidopsis/fisiologia , Proteínas de Arabidopsis/ultraestrutura , Proteínas de Transporte/fisiologia , Proteínas de Transporte/ultraestrutura , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Evolução Biológica , Proteínas de Transporte/metabolismo , Chlamydomonas/metabolismo , Eucariotos , Variação Genética/genética , Células Germinativas/metabolismo , Fusão de Membrana , Homologia de Sequência de Aminoácidos
16.
Plant Cell ; 30(8): 1824-1847, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-29997239

RESUMO

Plants and algae must tightly coordinate photosynthetic electron transport and metabolic activities given that they often face fluctuating light and nutrient conditions. The exchange of metabolites and signaling molecules between organelles is thought to be central to this regulation but evidence for this is still fragmentary. Here, we show that knocking out the peroxisome-located MALATE DEHYDROGENASE2 (MDH2) of Chlamydomonas reinhardtii results in dramatic alterations not only in peroxisomal fatty acid breakdown but also in chloroplast starch metabolism and photosynthesis. mdh2 mutants accumulated 50% more storage lipid and 2-fold more starch than the wild type during nitrogen deprivation. In parallel, mdh2 showed increased photosystem II yield and photosynthetic CO2 fixation. Metabolite analyses revealed a >60% reduction in malate, together with increased levels of NADPH and H2O2 in mdh2 Similar phenotypes were found upon high light exposure. Furthermore, based on the lack of starch accumulation in a knockout mutant of the H2O2-producing peroxisomal ACYL-COA OXIDASE2 and on the effects of H2O2 supplementation, we propose that peroxisome-derived H2O2 acts as a regulator of chloroplast metabolism. We conclude that peroxisomal MDH2 helps photoautotrophs cope with nitrogen scarcity and high light by transmitting the redox state of the peroxisome to the chloroplast by means of malate shuttle- and H2O2-based redox signaling.


Assuntos
Chlamydomonas/metabolismo , Chlamydomonas/fisiologia , Malato Desidrogenase/metabolismo , Fotossíntese/fisiologia , Dióxido de Carbono/metabolismo , Chlamydomonas/efeitos dos fármacos , Peróxido de Hidrogênio/farmacologia , Malato Desidrogenase/genética , Mutação/genética , Oxirredução/efeitos dos fármacos , Fotossíntese/efeitos dos fármacos , Fotossíntese/genética
17.
J Photochem Photobiol B ; 185: 111-116, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-29886329

RESUMO

Oxygenic photosynthesis is conducted by two photoactive units, photosystem I (PSI) and photosystem II (PSII), that utilize light energy to generate the electron flow from water to NADPH. Photosynthetic organisms have developed a mechanism called state transition (ST) to regulate the excitation balance between the two units, since the balance is constantly disturbed by fluctuation in light quality. The traditional ST model assumes shuttling of a light-harvesting complex called LHCII between the two PSs. However, there has been no direct observation of the intracellular rearrangements of LHCII upon ST, which is crucial in order to evaluate the validity of the traditional ST model. Here, the intracellular distributions of the two PSs and LHCII are visualized by using a novel cryogenic optical microscope. The calculated Pearson's correlation coefficient between the relative fluorescence intensity of LHCII and the fluorescence intensity ratio of PSII to PSI provided information about the degree of co-localization of these components. The analysis indicated that the relative emission intensity from LHCII is stronger in the PSII-abundant region than in the PSI-abundant one in both states. On the other hand, a statistical analysis by Welch's test indicated that Pearson's correlation coefficient is significantly higher in state1 than state2, probably reflecting the movement of LHCII from PSII to PSI upon state transition. The study also found an independent cell group in which degree of ST was between those observed for fully converted cells. These cells tended to show lower correlation coefficients than the fully converted ones. This was explained by assuming the existence of free LHCII, which moves to but remains unconnected to PSI in state2.


Assuntos
Chlamydomonas/metabolismo , Complexos de Proteínas Captadores de Luz/metabolismo , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Chlamydomonas/crescimento & desenvolvimento , Complexos de Proteínas Captadores de Luz/química , Microscopia de Fluorescência , Fotossíntese , Complexo de Proteína do Fotossistema I/química , Complexo de Proteína do Fotossistema II/química , Espectrometria de Fluorescência , Temperatura Ambiente
18.
J Microbiol Biotechnol ; 28(7): 1217-1224, 2018 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-29913549

RESUMO

Seaweed produce antioxidants to counteract environmental stresses, and these antioxidant genes are regarded as important defense strategies for marine algae. In this study, the expression of Pyropia yezoensis (Bangiales, Rhodophyta) ascorbate peroxidase (PyAPX) and manganese-superoxide dismutase (PyMnSOD) was examined by qRT-PCR in P. yezoensis blades under abiotic stress conditions. Furthermore, the functional relevance of these genes was explored by overexpressing them in Chlamydomonas. A comparison of the different expression levels of PyAPX and PyMnSOD after exposure to each stress revealed that both genes were induced by high salt and UVB exposure, being increased approximately 3-fold after 12 h. The expression of the PyAPX and PyMnSOD genes also increased following exposure to H2O2. When these two genes were overexpressed in Chlamydomonas, the cells had a higher growth rate than control cells under conditions of hydrogen peroxide-induced oxidative stress, increased salinity, and UV exposure. These data suggest that Chlamydomonas is a suitable model for studying the function of stress genes, and that PyAPX and PyMnSOD genes are involved in the adaptation and defense against stresses that alter metabolism.


Assuntos
Ascorbato Peroxidases/metabolismo , Chlamydomonas/genética , Chlamydomonas/metabolismo , Rodófitas/genética , Rodófitas/metabolismo , Estresse Fisiológico , Superóxido Dismutase/metabolismo , Adaptação Fisiológica , Antioxidantes/metabolismo , Chlamydomonas/crescimento & desenvolvimento , Chlamydomonas/efeitos da radiação , Regulação da Expressão Gênica de Plantas/efeitos da radiação , Peróxido de Hidrogênio/metabolismo , Estresse Oxidativo , Rodófitas/enzimologia , Salinidade , Superóxido Dismutase/genética , Transformação Genética
19.
Am J Hum Genet ; 102(5): 956-972, 2018 05 03.
Artigo em Inglês | MEDLINE | ID: mdl-29727692

RESUMO

Primary ciliary dyskinesia (PCD) is a genetically and phenotypically heterogeneous disorder characterized by destructive respiratory disease and laterality abnormalities due to randomized left-right body asymmetry. PCD is mostly caused by mutations affecting the core axoneme structure of motile cilia that is essential for movement. Genes that cause PCD when mutated include a group that encode proteins essential for the assembly of the ciliary dynein motors and the active transport process that delivers them from their cytoplasmic assembly site into the axoneme. We screened a cohort of affected individuals for disease-causing mutations using a targeted next generation sequencing panel and identified two unrelated families (three affected children) with mutations in the uncharacterized C11orf70 gene (official gene name CFAP300). The affected children share a consistent PCD phenotype from early life with laterality defects and immotile respiratory cilia displaying combined loss of inner and outer dynein arms (IDA+ODA). Phylogenetic analysis shows C11orf70 is highly conserved, distributed across species similarly to proteins involved in the intraflagellar transport (IFT)-dependant assembly of axonemal dyneins. Paramecium C11orf70 RNAi knockdown led to combined loss of ciliary IDA+ODA with reduced cilia beating and swim velocity. Tagged C11orf70 in Paramecium and Chlamydomonas localizes mainly in the cytoplasm with a small amount in the ciliary component. IFT139/TTC21B (IFT-A protein) and FLA10 (IFT kinesin) depletion experiments show that its transport within cilia is IFT dependent. During ciliogenesis, C11orf70 accumulates at the ciliary tips in a similar distribution to the IFT-B protein IFT46. In summary, C11orf70 is essential for assembly of dynein arms and C11orf70 mutations cause defective cilia motility and PCD.


Assuntos
Dineínas do Axonema/metabolismo , Transtornos da Motilidade Ciliar/genética , Proteínas do Citoesqueleto/genética , Flagelos/metabolismo , Mutação/genética , Proteínas Nucleares/genética , Alelos , Sequência de Aminoácidos , Dineínas do Axonema/ultraestrutura , Sequência de Bases , Transporte Biológico , Diferenciação Celular/genética , Chlamydomonas/metabolismo , Sequência Conservada/genética , Flagelos/ultraestrutura , Técnicas de Silenciamento de Genes , Proteínas de Fluorescência Verde/metabolismo , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Proteínas Nucleares/química , Paramecium/metabolismo , Paramecium/ultraestrutura , Transcrição Genética
20.
Aquat Toxicol ; 200: 62-72, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29727772

RESUMO

To better understand heavy metal tolerance in Chlamydomonas acidophila, an extremophilic green alga, we assembled its transcriptome and measured transcriptomic expression before and after Cd exposure in this and the neutrophilic model microalga Chlamydomonas reinhardtii. Genes possibly related to heavy metal tolerance and detoxification were identified and analyzed as potential key innovations that enable this species to live in an extremely acid habitat with high levels of heavy metals. In addition we provide a data set of single orthologous genes from eight green algal species as a valuable resource for comparative studies including eukaryotic extremophiles. Our results based on differential gene expression, detection of unique genes and analyses of codon usage all indicate that there are important genetic differences in C. acidophila compared to C. reinhardtii. Several efflux family proteins were identified as candidate key genes for adaptation to acid environments. This study suggests for the first time that exposure to cadmium strongly increases transposon expression in green algae, and that oil biosynthesis genes are induced in Chlamydomonas under heavy metal stress. Finally, the comparison of the transcriptomes of several acidophilic and non-acidophilic algae showed that the Chlamydomonas genus is polyphyletic and that acidophilic algae have distinctive aminoacid usage patterns.


Assuntos
Chlamydomonas/efeitos dos fármacos , Metais Pesados/toxicidade , Poluentes Químicos da Água/toxicidade , Actinas/genética , Actinas/metabolismo , Adaptação Fisiológica/efeitos dos fármacos , Cádmio/metabolismo , Cádmio/toxicidade , Hidrolases de Éster Carboxílico/classificação , Hidrolases de Éster Carboxílico/genética , Chlamydomonas/classificação , Chlamydomonas/metabolismo , Dioxigenases/classificação , Dioxigenases/genética , Tolerância a Medicamentos/genética , Metais Pesados/metabolismo , Filogenia , Proteínas de Plantas/classificação , Proteínas de Plantas/genética , RNA de Plantas/química , RNA de Plantas/isolamento & purificação , RNA de Plantas/metabolismo , RNA Ribossômico 18S/genética , RNA Ribossômico 18S/metabolismo , Análise de Sequência de RNA , Transcriptoma/efeitos dos fármacos , Poluentes Químicos da Água/química , Poluentes Químicos da Água/metabolismo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA