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1.
BMC Plant Biol ; 19(1): 350, 2019 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-31409298

RESUMO

BACKGROUND: The pentatricopeptide repeat (PPR) gene family, which contains multiple 35-amino acid repeats, constitutes one of the largest gene families in plants. PPR proteins function in organelles to target specific transcripts and are involved in plant development and growth. However, the function of PPR proteins in cotton is still unknown. RESULTS: In this study, we characterized a PPR gene YELLOW-GREEN LEAF (GhYGL1d) that is required for cotton plastid development. The GhYGL1d gene has a DYW domain in C-terminal and is highly express in leaves, localized to the chloroplast fractions. GhYGL1d share high amino acid-sequence homology with AtECB2. In atecb2 mutant, overexpression of GhYGL1d rescued the seedling lethal phenotype and restored the editing of accD and ndhF transcripts. Silencing of GhYGL1d led to the reduction of chlorophyll and phenotypically yellow-green leaves in cotton. Compared with wild type, GhYGL1d-silenced cotton showed significant deformations of thylakoid structures. Furthermore, the transcription levels of plastid-encoded polymerase (PEP) and nuclear-encoded polymerase (NEP) dependent genes were decreased in GhYGL1d-silenced cotton. CONCLUSIONS: Our data indicate that GhYGL1d not only contributes to the editing of accD and ndhF genes, but also affects the expression of NEP- and PEP-dependent genes to regulate the development of thylakoids, and therefore regulates leaf variegation in cotton.


Assuntos
Cloroplastos/genética , Gossypium/genética , Proteínas de Plantas/fisiologia , Cloroplastos/metabolismo , Cloroplastos/fisiologia , Gossypium/anatomia & histologia , Gossypium/metabolismo , Folhas de Planta/anatomia & histologia , Folhas de Planta/genética , Folhas de Planta/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo
2.
J Photochem Photobiol B ; 197: 111535, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31319267

RESUMO

Measurement of Pulse-Amplitude-Modulated (PAM) chlorophyll a fluorescence is widely used method for obtaining information on the functional state of photosystem II (PSII). Recently, it has been shown that some of long-established fluorescence parameters must be interpreted with caution, when the light-induced chloroplast movements occur. In our work we have analyzed the effect of chloroplast movements on these parameters. We have derived new parameters that are independent of the change in PSII absorption occurring during measurement. To verify whether there is a need for new parameters or the difference between the parameters commonly used and the newly derived ones is insignificant, we conducted an experiment with Arabidopsis thaliana wild type plants and its phot1 phot2 mutant defective in chloroplast movement. Plants were exposed to light of different qualities (450, 470, 550 or 660 nm) and quantities (100, 400 or 1200 µmol m-2 s-1) for up to 40 min. Since the blue light-induced chloroplast avoidance reaction is a photoprotective mechanism, we expected that phot1 phot2 mutant will compensate the lack of this mechanism by increasing non-photochemical quenching. However, using the light at both 450 and 470 nm, the calculation of commonly used parameter, ΦNPQ (quantum yield of regulated light-induced thermal energy dissipation in PSII) based on Hendrickson et al. [L. Hendrickson, R.T. Furbank, W.S. Chow, Photosynth. Res. 82 (2004) 73-81] showed the opposite. On the other hand, the results obtained using our newly proposed formulae to determine quantum yield of PSII thermal energy dissipation were in line with our assumption. Thus, the experimental data showed that some formulae of fluorescence parameters are dependent on the change in PSII absorption and need to be interpreted carefully. On the contrary, the formulae introduced by us can remove the effect of changes in PSII absorption that occur during measurement, without additional measurements, and give the real estimate of light-induced non-photochemical quenching.


Assuntos
Proteínas de Arabidopsis/metabolismo , Clorofila A/química , Complexo de Proteína do Fotossistema II/metabolismo , Arabidopsis/metabolismo , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/genética , Cloroplastos/fisiologia , Luz , Modelos Teóricos , Mutagênese , Complexo de Proteína do Fotossistema II/química , Complexo de Proteína do Fotossistema II/genética , Folhas de Planta/química , Teoria Quântica , Termodinâmica
3.
Plant Mol Biol ; 100(6): 635-645, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31147815

RESUMO

KEY MESSAGE: Rice WSL6 is involved in chloroplast ribosome biogenesis and is essential for early chloroplast development. Construction of the genetic translation system is a prerequisite for chloroplast development in plants. However, the molecular mechanism underlying this process is largely unknown. Here, we isolated a white stripe leaf6 (wsl6) mutant in rice. The mutant seedlings displayed white-striped leaves that were more severe under low-temperature conditions. Transmission electron microscopy analysis showed that the wsl6 mutant was defective in early chloroplast development. Map-based cloning revealed that WSL6 encodes an Era-type guanosine-5'-triphosphate (GTP)-binding protein located in chloroplasts. Immunoblotting and quantitative real-time polymerase chain reaction (qRT-PCR) analyses demonstrated an absence of 70S ribosomes in wsl6 chloroplasts. Further research showed that WSL6 binds to the 16S ribosomal RNA (rRNA) subunit of chloroplast ribosome 30S. In summary, these results show that WSL6 is essential for chloroplast ribosome biogenesis during early chloroplast development in rice.


Assuntos
Cloroplastos/fisiologia , Proteínas de Ligação ao GTP/metabolismo , Oryza/genética , Proteínas de Plantas/genética , Clonagem Molecular , Proteínas de Ligação ao GTP/fisiologia , Regulação da Expressão Gênica de Plantas , Teste de Complementação Genética , Microscopia Eletrônica de Transmissão , Mutação , Oryza/fisiologia , Fenótipo , Pigmentação , Proteínas de Plantas/fisiologia , Biossíntese de Proteínas , RNA Ribossômico 16S/genética , Temperatura Ambiente
5.
Int J Mol Sci ; 20(9)2019 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-31035645

RESUMO

Pyrimidine nucleotides are important metabolites that are building blocks of nucleic acids, which participate in various aspects of plant development. Only a few genes involved in pyrimidine metabolism have been identified in rice and the majority of their functions remain unclear. In this study, we used a map-based cloning strategy to isolate a UMPK gene in rice, encoding the UMP kinase that phosphorylates UMP to form UDP, from a recessive mutant with pale-green leaves. In the mutant, UDP content always decreased, while UTP content fluctuated with the development of leaves. Mutation of UMPK reduced chlorophyll contents and decreased photosynthetic capacity. In the mutant, transcription of plastid-encoded RNA polymerase-dependent genes, including psaA, psbB, psbC and petB, was significantly reduced, whereas transcription of nuclear-encoded RNA polymerase-dependent genes, including rpoA, rpoB, rpoC1, and rpl23, was elevated. The expression of UMPK was significantly induced by various stresses, including cold, heat, and drought. Increased sensitivity to cold stress was observed in the mutant, based on the survival rate and malondialdehyde content. High accumulation of hydrogen peroxide was found in the mutant, which was enhanced by cold treatment. Our results indicate that the UMP kinase gene plays important roles in regulating chloroplast development and stress response in rice.


Assuntos
Cloroplastos/fisiologia , Resposta ao Choque Frio , Núcleosídeo-Fosfato Quinase/metabolismo , Oryza/fisiologia , Desenvolvimento Vegetal , Clonagem Molecular , Resposta ao Choque Frio/genética , Regulação da Expressão Gênica de Plantas , Mutação , Núcleosídeo-Fosfato Quinase/genética , Fenótipo , Desenvolvimento Vegetal/genética , Plastídeos/genética , Transcrição Genética
6.
Planta ; 250(2): 643-655, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31144110

RESUMO

MAIN CONCLUSION: Trehalose increased drought tolerance of tomato plants, accompanied by reduced water loss and closed stomata, which was associated with the upregulated ABA signaling-related genes expression, but not in ABA accumulation. Drought is one of the principal abiotic stresses that negatively influence the growth of plant and yield. Trehalose has great agronomic potential to improve the stress tolerance of plants. However, little information is available on the role of ABA and its signaling components in trehalose-induced drought tolerance. The aim of this study is to elucidate the potential mechanism by which trehalose regulates ABA in response to drought stress. In this study, 6-week-old tomato (Solanum lycopersicum cv. Ailsa Craig) plants were treated with 0 or 15.0 mM trehalose solution. Results showed that trehalose treatment significantly enhanced drought tolerance of tomato plants, accompanied by encouraged stomatal closure and protected chloroplast ultrastructure. Compared with controls, trehalose-treated plants showed lower hydrogen peroxide content and higher antioxidant enzymes activities, which contributed to alleviate oxidative damage caused by drought. Moreover, trehalose treatment decreased ABA content, which was followed by the downregulation of ABA biosynthesis genes expression and the upregulation of ABA catabolism genes expression. In contrast, exogenous trehalose upregulated transcript levels of ABA signaling-related genes, including SlPYL1/3/4/5/6/7/9, SlSnRK2.3/4, SlAREB1/2, and SlDREB1. These results suggested that trehalose treatment enhanced drought tolerance of tomato plants, and it's ABA signaling rather than ABA metabolism that was involved in trehalose-induced drought tolerance in tomato plants. These findings provide evidence for the physiological role of trehalose and bring about a new understanding of the possible relationship between trehalose and ABA.


Assuntos
Ácido Abscísico/metabolismo , Lycopersicon esculentum/fisiologia , Reguladores de Crescimento de Planta/metabolismo , Proteínas de Plantas/metabolismo , Transdução de Sinais , Trealose/farmacologia , Cloroplastos/fisiologia , Cloroplastos/ultraestrutura , Secas , Lycopersicon esculentum/genética , Lycopersicon esculentum/ultraestrutura , Fenótipo , Proteínas de Plantas/genética , Estômatos de Plantas/genética , Estômatos de Plantas/fisiologia , Estômatos de Plantas/ultraestrutura , Estresse Fisiológico
7.
Plant Sci ; 284: 185-191, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31084871

RESUMO

Transcriptional activation of ascorbate biosynthesis-associated genes under illumination is one of the important steps in ascorbate pool size regulation in photosynthetic tissues. Several biological processes within chloroplasts such as photosynthesis are required for this activation, suggesting functional chloroplasts to play a key role. We herein found that when grown on agar plate, ascorbate content in Arabidopsis non-photosynthetic tissues, roots, are unexpectedly almost comparable to that in shoots. The high accumulation of ascorbate was particularly observed in root regions closer to the root-hypocotyl junction, in which chloroplast development occurred because of a direct exposure to light. When chloroplast development in roots were further stimulated by shoot removal, the expression of biosynthetic genes, especially VTC2 gene that encodes GDP-l-galactose phosphorylase, was activated, resulting in an increase in ascorbate pool size. These positive effects were canceled when the roots were treated with a photosynthetic inhibitor. A null mutation in the LONG HYPOCOTYL 5 (HY5) gene almost completely inhibited root greening as well as the VTC2 expression. Overall, these findings show that chloroplast development can trigger the expression of ascorbate biosynthesis-associated genes not only in leaves but also in roots.


Assuntos
Arabidopsis/metabolismo , Ácido Ascórbico/biossíntese , Cloroplastos/fisiologia , Raízes de Plantas/metabolismo , Arabidopsis/fisiologia , Ácido Ascórbico/metabolismo , Clorofila/metabolismo , Cloroplastos/metabolismo , Regulação da Expressão Gênica de Plantas , Genes de Plantas/fisiologia , Redes e Vias Metabólicas , Raízes de Plantas/fisiologia , Reação em Cadeia da Polimerase em Tempo Real
8.
Theor Appl Genet ; 132(7): 2069-2086, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30953093

RESUMO

KEY MESSAGE: The vsp gene was fine mapped to a 353.7-kb region, and a 201-bp deletion that affected chloroplast development and chlorophyll biosynthesis was found in the candidate gene GhPUR4. Virescent mutations can be used as marker traits in heterosis breeding and can also be used to research chloroplast development, chlorophyll biosynthesis and photosynthesis mechanisms. Here, we obtained a light-sensitive virescent mutant, vsp, that has reduced chlorophyll (Chl) content and abnormal chloroplast development. Then, the virescent space (vsp) gene in the vsp mutant was preliminarily mapped to a 38.32-Mb region of chromosome D04 using a high-density SNP genetic map with a total length of 5384.33 cM and 4472 bin markers. Furthermore, the vsp gene was narrowed down to a 353.7-kb region that contains 15 candidate genes using 484 virescent individuals from an F2 population. Sequence analysis of genes in this region showed that a 201-bp deletion was present in the Gh_D04G1108 (GhPUR4) gene in the vsp mutant. The 201-bp deletion of Gh_D04G1108 caused the deletion of 67 AAs in the GhPUR4 protein. Virus-induced gene silencing (VIGS) of GhPUR4 in normal plants caused reduced GhPUR4 gene expression levels, reduced Chl content, abnormal chloroplast development and virescent true leaves. This study could help us unravel the function of GhPUR4 in chloroplast development and Chl biosynthesis at the early developmental stages of the true leaves in cotton, which could promote the research and application of virescent mutations in cotton heterosis breeding.


Assuntos
Clorofila/análise , Cloroplastos/fisiologia , Mapeamento Cromossômico , Gossypium/genética , Sequência de Aminoácidos , Cloroplastos/ultraestrutura , Genes de Plantas , Gossypium/fisiologia , Microscopia Eletrônica de Transmissão , Fenótipo , Melhoramento Vegetal , Folhas de Planta/crescimento & desenvolvimento , Deleção de Sequência
9.
Gene ; 706: 32-42, 2019 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-31028868

RESUMO

The chloroplastic thioredoxins (Trxs), a family of thiol-disulphide oxidoreductases, are reduced by either ferredoxin (Fd)-dependent Trx reductase (FTR) or reduced nicotinamide adenine dinucleotide phosphate (NADPH)-dependent Trx reductase (NTR). Two Trx systems are present in chloroplasts including Trxs, Trx-like proteins, and reductase FTR and NTRC. FTR is the main reductant for Trxs in chloroplasts, while the flavoprotein NTRC integrates NTR and Trx activity, and plays multiple roles in the Calvin cycle, the oxidative pentose phosphate pathway (OPPP), anti-peroxidation, tetrapyrrole metabolism, ATP and starch synthesis, and photoperiodic regulation. In addition, not only there exists a reduction potential transfer pathway across the thylakoid membrane, but also FTR and NTRC coordinate with each other to regulate chloroplast redox homeostasis. Herein, we summarise the physiological functions of these two Trx reduction systems, discuss how both regulate redox homeostasis in plant plastids, and emphasize the significance of chloroplast thioredoxin systems in maintaining photosynthetic efficiency in plants.


Assuntos
Cloroplastos/metabolismo , Tiorredoxina Dissulfeto Redutase/fisiologia , Tiorredoxinas/fisiologia , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Cloroplastos/fisiologia , Ferredoxinas/metabolismo , Proteínas com Ferro-Enxofre , Oxirredução , Oxirredutases/metabolismo , Peroxirredoxinas/metabolismo , Fotossíntese/fisiologia , Plastídeos/metabolismo , Tiorredoxina Dissulfeto Redutase/metabolismo , Tiorredoxinas/metabolismo
10.
Plant Sci ; 280: 321-329, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30824011

RESUMO

Cysteine functions not only as an amino acid in proteins but also as a precursor for a large number of essential biomolecules. Cysteine is synthesized via the incorporation of sulfide to O-acetylserine under the catalysis of O-acetylserine(thiol)lyase (OASTL). In dicotyledonous Arabidopsis, nine OASTL genes have been reported. However, in their null mutants, only the mutant of CS26 encoding S-sulfocysteine synthase showed the visible phenotypic changes, displaying significantly small plants and pale-green leaves under long-day condition but not short-day condition. Up to now, no OASTL gene or mutant has been identified in monocotyledon. In this study, we isolated a green-revertible albino mutant gra78 in rice (Oryza sativa). Its albino phenotype at the early seedling stage was sensitive to temperature but independent of photoperiod. Map-based cloning revealed that candidate gene LOC_Os01g59920 of GRA78 encodes a putative S-sulfocysteine synthase showing significant similarity with Arabidopsis CS26. Complementation experiment confirmed that mutation in LOC_Os01g59920 accounted for the mutant phenotype of gra78. GRA78 is constitutively expressed in all tissues and its encoded protein is targeted to the chloroplast. In addition, qRT-PCR suggested that expression levels of four OASTL homolog genes and five photosynthetic genes were remarkably down-regulated.


Assuntos
Liases/metabolismo , Oryza/enzimologia , Cloroplastos/fisiologia , Cloroplastos/ultraestrutura , Liases/genética , Liases/ultraestrutura , Mutação , Oryza/genética , Oryza/crescimento & desenvolvimento , Oryza/ultraestrutura , Fenótipo , Fotossíntese , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Plântula/enzimologia , Plântula/genética , Plântula/crescimento & desenvolvimento , Plântula/ultraestrutura
11.
Plant Sci ; 281: 251-260, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30824058

RESUMO

Fern spores are unicellular structures produced by the sporophyte generation that give rise to the haploid gametophyte. When released from the sporangium, spores are desiccation tolerant (DT) in the royal fern (Osmunda regalis) and contain fully developed chloroplasts. As a consequence, this type of spores is called chlorophyllous spores (CS). Upon transfer to germination conditions, CS initiate a process of imbibition that suppresses DT in 72 h, before the germination starts. In parallel to such change in DT, thylakoids undergo a profound remodelling in composition and function. Firstly, sustained quenching of chlorophyll fluorescence is relaxed, giving rise to photochemically active CS, while lipid composition shifts from that of a resting structure to a metabolically active cell. Basically trigalactolipids decreased in favour of monogalactolipids, with a parallel desaturation of fatty acids. Storage lipids such as triacylglycerol were quickly depleted. These results highlight the importance of the structure of thylakoids lipid as a key to protect membrane integrity during desiccation, together with the saturation of fatty acids and the constitutive chlorophyll quenching to prevent oxidative damage. The CS used here, in which the same cell shifts from DT to sensitive strategy in 72 h, reveal their potential as unicellular models for future studies on DT.


Assuntos
Cloroplastos/metabolismo , Gleiquênias/metabolismo , Esporos/metabolismo , Cloroplastos/fisiologia , Gleiquênias/fisiologia , Germinação/fisiologia , Esporos/fisiologia , Tilacoides/metabolismo , Tilacoides/fisiologia
12.
Proc Natl Acad Sci U S A ; 116(12): 5665-5674, 2019 03 19.
Artigo em Inglês | MEDLINE | ID: mdl-30833407

RESUMO

In most eukaryotes, organellar genomes are transmitted preferentially by the mother, but molecular mechanisms and evolutionary forces underlying this fundamental biological principle are far from understood. It is believed that biparental inheritance promotes competition between the cytoplasmic organelles and allows the spread of so-called selfish cytoplasmic elements. Those can be, for example, fast-replicating or aggressive chloroplasts (plastids) that are incompatible with the hybrid nuclear genome and therefore maladaptive. Here we show that the ability of plastids to compete against each other is a metabolic phenotype determined by extremely rapidly evolving genes in the plastid genome of the evening primrose Oenothera Repeats in the regulatory region of accD (the plastid-encoded subunit of the acetyl-CoA carboxylase, which catalyzes the first and rate-limiting step of lipid biosynthesis), as well as in ycf2 (a giant reading frame of still unknown function), are responsible for the differences in competitive behavior of plastid genotypes. Polymorphisms in these genes influence lipid synthesis and most likely profiles of the plastid envelope membrane. These in turn determine plastid division and/or turnover rates and hence competitiveness. This work uncovers cytoplasmic drive loci controlling the outcome of biparental chloroplast transmission. Here, they define the mode of chloroplast inheritance, as plastid competitiveness can result in uniparental inheritance (through elimination of the "weak" plastid) or biparental inheritance (when two similarly "strong" plastids are transmitted).


Assuntos
Cloroplastos/genética , Cloroplastos/fisiologia , Oenothera biennis/metabolismo , Acetil-CoA Carboxilase/genética , Evolução Biológica , Núcleo Celular/genética , Citoplasma/genética , Eucariotos/genética , Genoma , Genomas de Plastídeos/genética , Genótipo , Lipídeos/biossíntese , Oenothera biennis/fisiologia , Proteínas de Plantas/genética , Plastídeos/genética
13.
Plant Physiol ; 179(4): 1723-1738, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30718347

RESUMO

Plastid isoprenoids, a diverse group of compounds that includes carotenoids, chlorophylls, tocopherols, and multiple hormones, are essential for plant growth and development. Here, we identified and characterized SEED CAROTENOID DEFICIENT (SCD), which encodes an enzyme that functions in the biosynthesis of plastid isoprenoids in maize (Zea mays). SCD converts 2C-methyl-d-erytrithol 2,4-cyclodiphosphate to 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate in the penultimate step of the methylerythritol phosphate (MEP) pathway. In scd mutants, plant growth and development are impaired and the levels of MEP-derived isoprenoids, such as carotenoids, chlorophylls, and tocopherols, as well as abscisic and gibberellic acids, are reduced in leaves and seeds. This scd metabolic alteration varies among plant tissues and under different light conditions. RNA-sequencing of the scd mutant and wild type identified a limited number of differentially expressed genes in the MEP pathway, although isoprenoid levels were significantly reduced in scd seeds and dark-grown leaves. Furthermore, SCD-overexpressing transgenic lines showed little or no differences in isoprenoid levels, indicating that SCD may be subject to posttranslational regulation or not represent a rate-limiting step in the MEP pathway. These results enhance our understanding of the transcriptomic and metabolic regulatory roles of enzymes in the MEP pathway and of their effects on downstream isoprenoid pathways in various plant tissues and under different light conditions.


Assuntos
Proteínas de Plantas/fisiologia , Zea mays/metabolismo , Carotenoides/metabolismo , Cloroplastos/genética , Cloroplastos/fisiologia , Mapeamento Cromossômico , Clonagem Molecular , Eritritol/análogos & derivados , Eritritol/metabolismo , Regulação da Expressão Gênica de Plantas , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Plastídeos/metabolismo , Fosfatos Açúcares/genética , Fosfatos Açúcares/metabolismo , Terpenos/metabolismo , Zea mays/genética , Zea mays/crescimento & desenvolvimento
14.
Planta ; 249(4): 1189-1205, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30603788

RESUMO

MAIN CONCLUSION: Photoacclimation to variable light and photoperiod regimes in C. vulgaris represents a complex interplay between "biogenic" phytochrome-mediated sensing and "operational" redox sensing signaling pathways. Chlorella vulgaris Beijerinck UTEX 265 exhibits a yellow-green phenotype when grown under high light (HL) in contrast to a dark green phenotype when grown at low light (LL). The redox state of the photosynthetic electron transport chain (PETC) as estimated by excitation pressure has been proposed to govern this phenotypic response. We hypothesized that if the redox state of the PETC was the sole regulator of the HL phenotype, C. vulgaris should photoacclimate in response to the steady-state excitation pressure during the light period regardless of the length of the photoperiod. As expected, LL-grown cells exhibited a dark green phenotype, low excitation pressure (1 - qP = 0.22 ± 0.02), high chlorophyll (Chl) content (375 ± 77 fg Chl/cell), low Chl a/b ratio (2.97 ± 0.18) as well as high photosynthetic efficiency and photosynthetic capacity regardless of the photoperiod. In contrast, C. vulgaris grown under continuous HL developed a yellow-green phenotype characterized by high excitation pressure (1 - qP = 0.68 ± 0.01), a relatively low Chl content (180 ± 53 fg Chl/cell), high Chl a/b ratio (6.36 ± 0.54) with concomitantly reduced light-harvesting polypeptide abundance, as well as low photosynthetic capacity and efficiency measured on a per cell basis. Although cells grown under HL and an 18 h photoperiod developed a typical yellow-green phenotype, cells grown at HL but a 12 h photoperiod exhibited a dark green phenotype comparable to LL-grown cells despite exhibiting growth under high excitation pressure (1 - qP = 0.80 ± 0.04). The apparent uncoupling of excitation pressure and phenotype in HL-grown cells and a 12 h photoperiod indicates that chloroplast redox status cannot be the sole regulator of photoacclimation in C. vulgaris. We conclude that photoacclimation in C. vulgaris to HL is dependent upon growth history and reflects a complex interaction of endogenous systems that sense changes in photoperiod as well as photosynthetic redox balance.


Assuntos
Chlorella vulgaris/metabolismo , Cloroplastos/metabolismo , Chlorella vulgaris/crescimento & desenvolvimento , Chlorella vulgaris/fisiologia , Chlorella vulgaris/efeitos da radiação , Clorofila A/metabolismo , Cloroplastos/fisiologia , Transporte de Elétrons , Eletroforese em Gel de Poliacrilamida , Immunoblotting , Luz , Oxirredução , Fenótipo , Fotoperíodo , Fotossíntese/efeitos da radiação
15.
Microscopy (Oxf) ; 68(1): 13-36, 2019 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-30576547

RESUMO

The haploid gametophyte generation of ferns is an excellent experimental material for cell biology studies because of its simple structure and high sensitivity to light. Each step of the developmental process, such as cell growth, cell cycle and the direction of cell division, is controlled, step by step, by light, unlike what happens in complex seed plant tissues. To perform analyses at the cell or organelle level, we have developed special tools, instruments and techniques, such as a cuvette suitable for repeated centrifugation in particular directions, microbeam irradiators for partial cell irradiation and single-cell ligation technique to create enucleated cells. Some of our main discoveries are as follows: (1) changes in the intracellular position of the nucleus in long protonemal cells by centrifugation revealed that the nuclear position or a factor(s) that is/are co-centrifuged with the nucleus is important for the decision regarding the place of the formation of preprophase bands and the timing of their disappearance, which determines the position where the new cell wall attaches to the mother cell wall; (2) even within a single cell, various phenomena could be induced by blue or red light, with the localization of the blue or red light receptors being different depending on the phenomenon; (3) de novo mRNA synthesis is not involved in the signal transduction pathways underlying light-induced chloroplast movements. In this review article, various microscopic techniques, in addition to the results of physiology studies in fern gametophytes, are described.


Assuntos
Adiantum/crescimento & desenvolvimento , Divisão Celular/fisiologia , Células Germinativas Vegetais/crescimento & desenvolvimento , Células Vegetais/fisiologia , Núcleo Celular/fisiologia , Cloroplastos/fisiologia , Luz , Fotorreceptores de Plantas/fisiologia , Transdução de Sinais/fisiologia
16.
J Plant Physiol ; 232: 141-150, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30537601

RESUMO

Sesuvium portulacastrum, an important mangrove-associated true halophyte belongs to the family Aizoaceae, has excellent salt tolerance. Chloroplasts are the most sensitive organelles involved in the response to salinity. However, the regulation mechanism of chloroplasts of S. portulacastrum under salinity stress has not been reported. In this study, morphological and physiological analyses of leaves and comparative proteomics of chloroplasts isolated from the leaves of S. portulacastrum under different NaCl treatments were performed. Our results showed that the thickness of the palisade tissue, the leaf area, the maximum photochemical efficiency of photosystem II, and the electron transport rate increased remarkably after the plants were subjected to differential saline environments, indicating that salinity can increase photosynthetic efficiency and improve the growth of S. portulacastrum. Subsequently, 55 differentially expressed protein species (DEPs) from the chloroplasts of S. portulacastrum under differential salt conditions were positively identified by mass spectrometry. These DEPs were involved in multiple metabolic pathways, such as photosynthesis, carbon metabolism, ATP synthesis and the cell structure. Among these DEPs, the abundance of most proteins was induced by salt stress. Based on a combination of the morphological and physiological data, as well as the chloroplast proteome results, we speculated that S. portulacastrum can maintain photosynthetic efficiency and growth by maintaining the stability of the photosystem II complex, promoting the photochemical reaction rate, enhancing carbon fixation, developing plastoglobules, and preserving the biomembrane system of chloroplasts under salt stress.


Assuntos
Aizoaceae/fisiologia , Cloroplastos/fisiologia , Aizoaceae/metabolismo , Clorofila/metabolismo , Cloroplastos/metabolismo , Fotossíntese , Proteômica , Reação em Cadeia da Polimerase em Tempo Real , Estresse Salino , Plantas Tolerantes a Sal/metabolismo , Plantas Tolerantes a Sal/fisiologia , Solo
17.
J Vis Exp ; (142)2018 12 10.
Artigo em Inglês | MEDLINE | ID: mdl-30582588

RESUMO

The chloroplast is an essential organelle that is responsible for various cellular processes in plants, such as photosynthesis and the production of many secondary metabolites and lipids. Chloroplasts require a large number of proteins for these various physiological processes. Over 95% of chloroplast proteins are nucleus-encoded and imported into chloroplasts from the cytosol after translation on cytosolic ribosomes. Thus, the proper import or targeting of these nucleus-encoded chloroplast proteins to chloroplasts is essential for the proper functioning of chloroplasts as well as the plant cell. Nucleus-encoded chloroplast proteins contain signal sequences for specific targeting to chloroplasts. Molecular machinery localized to the chloroplast or cytosol recognize these signals and carry out the import process. To investigate the mechanisms of protein import or targeting to chloroplasts in vivo, we developed a rapid, efficient protoplast-based method to analyze protein import into chloroplasts of Arabidopsis. In this method, we use protoplasts isolated from leaf tissues of Arabidopsis. Here, we provide a detailed protocol for using protoplasts to investigate the mechanism by which proteins are imported into chloroplasts.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/citologia , Cloroplastos/fisiologia , Protoplastos/metabolismo , Arabidopsis/metabolismo , Núcleo Celular/metabolismo , Citosol/metabolismo , Folhas de Planta/citologia , Folhas de Planta/metabolismo , Proteínas de Plantas/metabolismo , Sinais Direcionadores de Proteínas , Transporte Proteico
18.
J Plant Res ; 131(5): 727-734, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29948488

RESUMO

Chloroplasts (plastids) and mitochondria evolved from endosymbiotic bacteria. These organelles perform vital functions in photosynthetic eukaryotes, such as harvesting and converting energy for use in biological processes. Consistent with their evolutionary origins, plastids and mitochondria proliferate by the binary fission of pre-existing organelles. Here, I review the structures and functions of the supramolecular machineries driving plastid and mitochondrial division, which were discovered and first studied in the primitive red alga Cyanidioschyzon merolae. In the past decade, intact division machineries have been isolated from plastids and mitochondria and examined to investigate their underlying structure and molecular mechanisms. A series of studies has elucidated how these division machineries assemble and transform during the fission of these organelles, and which of the component proteins generate the motive force for their contraction. Plastid- and mitochondrial-division machineries have important similarities in their structures and mechanisms despite sharing no component proteins, implying that these division machineries evolved in parallel. The establishment of these division machineries might have enabled the host eukaryotic ancestor to permanently retain these endosymbiotic organelles by regulating their binary fission and the equal distribution of resources to daughter cells. These findings provide key insights into the establishment of endosymbiotic organelles and have opened new avenues of research into their evolution and mechanisms of proliferation.


Assuntos
Organelas/ultraestrutura , Rodófitas/ultraestrutura , Simbiose , Divisão Celular , Cloroplastos/fisiologia , Cloroplastos/ultraestrutura , Mitocôndrias/fisiologia , Mitocôndrias/ultraestrutura , Organelas/fisiologia , Plastídeos/fisiologia , Plastídeos/ultraestrutura , Rodófitas/fisiologia
19.
J Plant Physiol ; 224-225: 173-182, 2018 May - Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29680783

RESUMO

One of the main mechanisms blocking translation after stress situations is mediated by phosphorylation of the α-subunit of the eukaryotic initiation factor 2 (eIF2), performed in Arabidopsis by the protein kinase GCN2 which interacts and is activated by ILITHYIA(ILA). ILA is involved in plant immunity and its mutant lines present phenotypes not shared by the gcn2 mutants. The functional link between these two genes remains elusive in plants. In this study, we show that, although both ILA and GCN2 genes are necessary to mediate eIF2α phosphorylation upon treatments with the aromatic amino acid biosynthesis inhibitor glyphosate, their mutants develop distinct root and chloroplast phenotypes. Electron microscopy experiments reveal that ila mutants, but not gcn2, are affected in chloroplast biogenesis, explaining the macroscopic phenotype previously observed for these mutants. ila3 mutants present a complex transcriptional reprogramming affecting defense responses, photosynthesis and protein folding, among others. Double mutant analyses suggest that ILA has a distinct function which is independent of GCN2 and eIF2α phosphorylation. These results suggest that these two genes may have common but also distinct functions in Arabidopsis.


Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/fisiologia , Cloroplastos/fisiologia , Peptídeos e Proteínas de Sinalização Intracelular/genética , Organogênese Vegetal/genética , Raízes de Plantas/crescimento & desenvolvimento , Proteínas Quinases/genética , Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Fator de Iniciação 2 em Eucariotos/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Fosforilação , Raízes de Plantas/genética , Proteínas Quinases/metabolismo
20.
Essays Biochem ; 62(1): 1-11, 2018 04 13.
Artigo em Inglês | MEDLINE | ID: mdl-29653966

RESUMO

A convergence of global factors is adding to the difficulties of securing a sustainable supply of food and feed to support the increasing global population. The positive impact of the rise in atmospheric CO2 on photosynthesis is more than offset by the increase in average global temperatures accompanying the change in atmospheric composition. This article provides a brief overview of how these adverse events affect some of the critical molecular processes of the chloroplast and by extension how this impacts the yields of the major crops. Although the tools are available to introduce genetic elements in most crops that will mitigate these adverse factors, the time needed to validate and optimize these traits can be extensive. There is a major concern that at the current rate of change to atmospheric composition and the accompanying rise in temperature the benefits of these traits may be rendered less effective soon after their introduction.


Assuntos
Atmosfera , Dióxido de Carbono/análise , Cloroplastos/fisiologia , Abastecimento de Alimentos , Fotossíntese , Transporte Biológico , Cloroplastos/metabolismo , Mudança Climática , Emigração e Imigração , Humanos , Umidade , Temperatura Ambiente
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