共查询到20条相似文献，搜索用时 15 毫秒
1.
Tiago Barros Antoine Royant Jörg Standfuss Andreas Dreuw Werner Kühlbrandt 《The EMBO journal》2009,28(3):298-306
Plants dissipate excess excitation energy as heat by non‐photochemical quenching (NPQ). NPQ has been thought to resemble in vitro aggregation quenching of the major antenna complex, light harvesting complex of photosystem II (LHC‐II). Both processes are widely believed to involve a conformational change that creates a quenching centre of two neighbouring pigments within the complex. Using recombinant LHC‐II lacking the pigments implicated in quenching, we show that they have no particular role. Single crystals of LHC‐II emit strong, orientation‐dependent fluorescence with an emission maximum at 680 nm. The average lifetime of the main 680 nm crystal emission at 100 K is 1.31 ns, but only 0.39 ns for LHC‐II aggregates under identical conditions. The strong emission and comparatively long fluorescence lifetimes of single LHC‐II crystals indicate that the complex is unquenched, and that therefore the crystal structure shows the active, energy‐transmitting state of LHC‐II. We conclude that quenching of excitation energy in the light‐harvesting antenna is due to the molecular interaction with external pigments in vitro or other pigment–protein complexes such as PsbS in vivo, and does not require a conformational change within the complex. 相似文献
2.
Hugues Nziengui Sonia Irigoyen Renáta Ünnep Ottó Zsiros Gergely Nagy Győző Garab Henrik Aronsson Wayne K. Versaw Cornelia Spetea 《The Plant journal : for cell and molecular biology》2015,84(1):99-110
The Arabidopsis phosphate transporter PHT4;1 was previously localized to the chloroplast thylakoid membrane. Here we investigated the physiological consequences of the absence of PHT4;1 for photosynthesis and plant growth. In standard growth conditions, two independent Arabidopsis knockout mutant lines displayed significantly reduced leaf size and biomass but normal phosphorus content. When mutants were grown in high‐phosphate conditions, the leaf phosphorus levels increased and the growth phenotype was suppressed. Photosynthetic measurements indicated that in the absence of PHT4;1 stromal phosphate was reduced to levels that limited ATP synthase activity. This resulted in reduced CO2 fixation and accumulation of soluble sugars, limiting plant growth. The mutants also displayed faster induction of non‐photochemical quenching than the wild type, in line with the increased contribution of ΔpH to the proton‐motive force across thylakoids. Small‐angle neutron scattering showed a smaller lamellar repeat distance, whereas circular dichroism spectroscopy indicated a perturbed long‐range order of photosystem II (PSII) complexes in the mutant thylakoids. The absence of PHT4;1 did not alter the PSII repair cycle, as indicated by wild‐type levels of phosphorylation of PSII proteins, inactivation and D1 protein degradation. Interestingly, the expression of genes for several thylakoid proteins was downregulated in the mutants, but the relative levels of the corresponding proteins were either not affected or could not be discerned. Based on these data, we propose that PHT4;1 plays an important role in chloroplast phosphate compartmentation and ATP synthesis, which affect plant growth. It also maintains the ionic environment of thylakoids, which affects the macro‐organization of complexes and induction of photoprotective mechanisms. 相似文献
3.
Goral TK Johnson MP Duffy CD Brain AP Ruban AV Mullineaux CW 《The Plant journal : for cell and molecular biology》2012,69(2):289-301
We characterized a set of Arabidopsis mutants deficient in specific light-harvesting proteins, using freeze-fracture electron microscopy to probe the organization of complexes in the membrane and confocal fluorescence recovery after photobleaching to probe the dynamics of thylakoid membranes within intact chloroplasts. The same methods were used to characterize mutants lacking or over-expressing PsbS, a protein related to light-harvesting complexes that appears to play a role in regulation of photosynthetic light harvesting. We found that changes in the complement of light-harvesting complexes and PsbS have striking effects on the photosystem II macrostructure, and that these effects correlate with changes in the mobility of chlorophyll proteins within the thylakoid membrane. The mobility of chlorophyll proteins was found to correlate with the extent of photoprotective non-photochemical quenching, consistent with the idea that non-photochemical quenching involves extensive re-organization of complexes in the membrane. We suggest that a key feature of the physiological function of PsbS is to decrease the formation of ordered semi-crystalline arrays of photosystem II in the low-light state. Thus the presence of PsbS leads to an increase in the fluidity of the membrane, accelerating the re-organization of the photosystem II macrostructure that is necessary for induction of non-photochemical quenching. 相似文献
4.
Stefanie Tietz Christopher C. Hall Jeffrey A. Cruz David M. Kramer 《Plant, cell & environment》2017,40(8):1243-1255
In photosynthesis, light energy is absorbed by light‐harvesting complexes and used to drive photochemistry. However, a fraction of absorbed light is lost to non‐photochemical quenching (NPQ) that reflects several important photosynthetic processes to dissipate excess energy. Currently, estimates of NPQ and its individual components (qE, qI, qZ and qT) are measured from pulse‐amplitude‐modulation (PAM) measurements of chlorophyll fluorescence yield and require measurements of the maximal yield of fluorescence in fully dark‐adapted material (Fm), when NPQ is assumed to be negligible. Unfortunately, this approach requires extensive dark acclimation, often precluding widespread or high‐throughput use, particularly under field conditions or in imaging applications, while introducing artefacts when Fm is measured in the presence of residual photodamaged centres. To address these limitations, we derived and characterized a new set of parameters, NPQ(T), and its components that can be (1) measured in a few seconds, allowing for high‐throughput and field applications; (2) does not require full relaxation of quenching processes and thus can be applied to photoinhibited materials; (3) can distinguish between NPQ and chloroplast movements; and (4) can be used to image NPQ in plants with large leaf movements. We discuss the applications benefits and caveats of both approaches. 相似文献
5.
A. K. Calzavara J. S. Rocha G. Lourenço K. Sanada C. Medri E. Bianchini J. A. Pimenta R. Stolf‐Moreira H. C. Oliveira 《Plant biology (Stuttgart, Germany)》2017,19(5):720-727
- The re‐composition of deforested environments requires the prior acclimation of seedlings to full sun in nurseries. Seedlings can overcome excess light either through the acclimation of pre‐existing fully expanded leaves or through the development of new leaves that are acclimated to the new light environment. Here, we compared the acclimation capacity of mature (MatL, fully expanded at the time of transfer) and newly expanded (NewL, expanded after the light shift) leaves of Guazuma ulmifolia Lam. (Malvaceae) seedlings to high light.
- The seedlings were initially grown under shade and then transferred to full sunlight. MatL and NewL were used for chlorophyll fluorescence and gas exchange analyses, pigment extraction and morpho‐anatomical measurements.
- After the transfer of seedlings to full sun, the MatL persisted and acclimated to some extent to the new light condition, since they underwent alterations in some morpho‐physiological traits and maintained a functional electron transport chain and positive net photosynthesis rate. However, long‐term exposure to high light led to chronic photoinhibition in MatL, which could be related to the limited plasticity of leaf morpho‐anatomical attributes. However, the NewL showed a high capacity to use the absorbed energy in photochemistry and dissipate excess energy harmlessly, attributes that were favoured by the high structural plasticity exhibited by these leaves.
- Both the maintenance of mature, photosynthetically active leaves and the production of new leaves with a high capacity to cope with excess energy were important for acclimation of G. ulmifolia seedlings.
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7.
Siddhartha Dutta Jeffrey A. Cruz Yuhua Jiao Jin Chen Katherine W. Osteryoung 《The Plant journal : for cell and molecular biology》2015,84(2):428-442
Leaf chloroplast movement is thought to optimize light capture and to minimize photodamage. To better understand the impact of chloroplast movement on photosynthesis, we developed a technique based on the imaging of reflectance from leaf surfaces that enables continuous, high‐sensitivity, non‐invasive measurements of chloroplast movement in multiple intact plants under white actinic light. We validated the method by measuring photorelocation responses in Arabidopsis chloroplast division mutants with drastically enlarged chloroplasts, and in phototropin mutants with impaired photorelocation but normal chloroplast morphology, under different light regimes. Additionally, we expanded our platform to permit simultaneous image‐based measurements of chlorophyll fluorescence and chloroplast movement. We show that chloroplast division mutants with enlarged, less‐mobile chloroplasts exhibit greater photosystem II photodamage than is observed in the wild type, particularly under fluctuating high levels of light. Comparison between division mutants and the severe photorelocation mutant phot1‐5 phot2‐1 showed that these effects are not entirely attributable to diminished photorelocation responses, as previously hypothesized, implying that altered chloroplast morphology affects other photosynthetic processes. Our dual‐imaging platform also allowed us to develop a straightforward approach to correct non‐photochemical quenching (NPQ) calculations for interference from chloroplast movement. This correction method should be generally useful when fluorescence and reflectance are measured in the same experiments. The corrected data indicate that the energy‐dependent (qE) and photoinhibitory (qI) components of NPQ contribute differentially to the NPQ phenotypes of the chloroplast division and photorelocation mutants. This imaging technology thus provides a platform for analyzing the contributions of chloroplast movement, chloroplast morphology and other phenotypic attributes to the overall photosynthetic performance of higher plants. 相似文献
8.
Lauriebeth Leonelli Erika Erickson Dagmar Lyska Krishna K. Niyogi 《The Plant journal : for cell and molecular biology》2016,88(3):375-386
Plants must switch rapidly between light harvesting and photoprotection in response to environmental fluctuations in light intensity. This switch can lead to losses in absorbed energy usage, as photoprotective energy dissipation mechanisms can take minutes to hours to fully relax. One possible way to improve photosynthesis is to engineer these energy dissipation mechanisms (measured as non‐photochemical quenching of chlorophyll a fluorescence, NPQ) to induce and relax more quickly, resulting in smaller losses under dynamic light conditions. Previous studies aimed at understanding the enzymes involved in the regulation of NPQ have relied primarily on labor‐intensive and time‐consuming generation of stable transgenic lines and mutant populations – approaches limited to organisms amenable to genetic manipulation and mapping. To enable rapid functional testing of NPQ‐related genes from diverse organisms, we performed Agrobacterium tumefaciens‐mediated transient expression assays in Nicotiana benthamiana to test if NPQ kinetics could be modified in fully expanded leaves. By expressing Arabidopsis thaliana genes known to be involved in NPQ, we confirmed the viability of this method for studying dynamic photosynthetic processes. Subsequently, we used naturally occurring variation in photosystem II subunit S, a modulator of NPQ in plants, to explore how differences in amino acid sequence affect NPQ capacity and kinetics. Finally, we functionally characterized four predicted carotenoid biosynthesis genes from the marine algae Nannochloropsis oceanica and Thalassiosira pseudonana and examined the effect of their expression on NPQ in N. benthamiana. This method offers a powerful alternative to traditional gene characterization methods by providing a fast and easy platform for assessing gene function in planta. 相似文献
9.
缺铁使大豆叶片激发能的耗散增加 总被引：12，自引：2，他引：12
缺铁叶片的光合速率大幅度下降。这种降低可能不是色素含量降低的结果 ;而且缺铁对PSII复合物的活性影响很小 ;较高的PQ还原程度显示缺铁叶片PSII受体侧电子传递受阻 ,这可能是导致光合速率下降的主要因素。强光下缺铁叶片的天线转化效率比正常叶片低 ,用于光化学反应的激发能很少。缺铁导致大豆叶片激发能耗散增加。通过抑制剂处理和叶黄素组分的分析 ,可以认为在耗散过剩激发能的过程中 ,缺铁叶片充分启动了叶黄素循环 相似文献
10.
Most spontaneous mutations affecting fitness are likely to be deleterious, but the strength of selection acting on them might be impacted by environmental stress. Such stress‐dependent selection could expose hidden genetic variation, which in turn might increase the adaptive potential of stressed populations. On the other hand, this variation might represent a genetic load and thus lead to population extinction under stress. Previous studies to determine the link between stress and mutational effects on fitness, however, have produced inconsistent results. Here, we determined the net change in fitness in 29 genotypes of the green algae Chlamydomonas reinhardtii that accumulated mutations in the near absence of selection for approximately 1000 generations across two stress gradients, increasing NaCl and decreasing phosphate. We found mutational effects to be magnified under extremely stressful conditions, but such effects were specific both to the type of stress and to the genetic background. The detection of stress‐dependent fitness effects of mutations depended on accurately scaling relative fitness measures by generation times, thus offering an explanation for the inconsistencies among previous studies. 相似文献
11.
Glycolate is produced in autotrophic cells under high temperatures and Ci‐limitation via oxygenation of ribulose‐1,5‐bisphosphate. In unicellular algae, glycolate is lost via excretion or metabolized via the C2 cycle by consuming reductants, ATP and CO2 emission (photorespiration). Therefore, photorespiration is an inhibitory process for biomass production. However, cells can be manipulated in a way that they become glycolate‐producing ‘cell factories’, when the ratio carboxylation/oxygenation is 2. If under these conditions the C2 cycle is blocked, glycolate excretion becomes the only pathway of photosynthetic carbon flow. The study aims to proof the biotechnological applicability of algal‐based glycolate excretion as a new biotechnological platform. It is shown that cells of Chlamydomonas can be cultivated under specific conditions to establish a constant and long‐term stable glycolate excretion during the light phase. The cultures achieved a high efficiency of 82% of assimilated carbon transferred into glycolate biosynthesis without losses of function in cell vitality. Moreover, the glycolate accumulation in the medium is high enough to be directly used for microbial fermentation but does not show toxic effects to the glycolate‐producing cells. 相似文献
12.
Jacopo Martinis Gaétan Glauser Sergiu Valimareanu Michaela Stettler Samuel C. Zeeman Hiroshi Yamamoto Toshiharu Shikanai Felix Kessler 《The Plant journal : for cell and molecular biology》2014,77(2):269-283
Arabidopsis proton gradient regulation (pgr) mutants have high chlorophyll fluorescence and reduced non‐photochemical quenching (NPQ) caused by defects in photosynthetic electron transport. Here, we identify PGR6 as the chloroplast lipid droplet (plastoglobule, PG) kinase ABC1K1 (activity of bc1 complex kinase 1). The members of the ABC1/ADCK/UbiB family of atypical kinases regulate ubiquinone synthesis in bacteria and mitochondria, and impact various metabolic pathways in plant chloroplasts. Here, we demonstrate that abc1k1 has a unique photosynthetic and metabolic phenotype that is distinct from that of the abc1k3 homolog. The abc1k1/pgr6 single mutant is specifically deficient in the electron carrier plastoquinone, as well as in β–carotene and the xanthophyll lutein, and is defective in membrane antioxidant tocopherol metabolism. After 2 days of continuous high light stress, abc1k1/pgr6 plants suffer extensive photosynthetic and metabolic perturbations, strongly affecting carbohydrate metabolism. Remarkably, however, the mutant acclimates to high light after 7 days together with a recovery of carotenoid levels and a drastic alteration in the starch‐to‐sucrose ratio. Moreover, ABC1K1 behaves as an active kinase and phosphorylates VTE1, a key enzyme of tocopherol (vitamin E) metabolism in vitro. Our results indicate that the ABC1K1 kinase constitutes a new type of regulatory link between photosynthetic activity and chloroplast metabolism. 相似文献
13.
Bat‐Chen Wolf Tal Isaacson Vivekanand Tiwari Inbal Dangoor Sapir Mufkadi Avihai Danon 《The Plant journal : for cell and molecular biology》2020,103(2):715-725
PGR5‐LIKE PHOTOSYNTHETIC PHENOTYPE1 (PGRL1) regulates photosystem I cyclic electron flow which transiently activates non‐photochemical quenching at the onset of light. Here, we show that a disulfide‐based mechanism of PGRL1 regulated this process in vivo at the onset of low light levels. We found that PGRL1 regulation depended on active formation of key regulatory disulfides in the dark, and that PGR5 was required for this activity. The disulfide state of PGRL1 was modulated in plants by counteracting reductive and oxidative components and reached a balanced state that depended on the light level. We propose that the redox regulation of PGRL1 fine‐tunes a timely activation of photosynthesis at the onset of low light. 相似文献
14.
Stefanie J. Müller‐Schüssele Ren Wang Desire D. Gütle Jill Romer Marta Rodriguez‐Franco Martin Scholz Felix Buchert Volker M. Lüth Stanislav Kopriva Peter Drmann Markus Schwarzlnder Ralf Reski Michael Hippler Andreas J. Meyer 《The Plant journal : for cell and molecular biology》2020,103(3):1140-1154
Thiol‐based redox‐regulation is vital for coordinating chloroplast functions depending on illumination and has been throroughly investigated for thioredoxin‐dependent processes. In parallel, glutathione reductase (GR) maintains a highly reduced glutathione pool, enabling glutathione‐mediated redox buffering. Yet, how the redox cascades of the thioredoxin and glutathione redox machineries integrate metabolic regulation and detoxification of reactive oxygen species remains largely unresolved because null mutants of plastid/mitochondrial GR are embryo‐lethal in Arabidopsis thaliana. To investigate whether maintaining a highly reducing stromal glutathione redox potential (EGSH) via GR is necessary for functional photosynthesis and plant growth, we created knockout lines of the homologous enzyme in the model moss Physcomitrella patens. In these viable mutant lines, we found decreasing photosynthetic performance and plant growth with increasing light intensities, whereas ascorbate and zeaxanthin/antheraxanthin levels were elevated. By in vivo monitoring stromal EGSH dynamics, we show that stromal EGSH is highly reducing in wild‐type and clearly responsive to light, whereas an absence of GR leads to a partial glutathione oxidation, which is not rescued by light. By metabolic labelling, we reveal changing protein abundances in the GR knockout plants, pinpointing the adjustment of chloroplast proteostasis and the induction of plastid protein repair and degradation machineries. Our results indicate that the plastid thioredoxin system is not a functional backup for the plastid glutathione redox systems, whereas GR plays a critical role in maintaining efficient photosynthesis. 相似文献
15.
Marjaana Suorsa Marjaana Rantala Fikret Mamedov Maija Lespinasse Andrea Trotta Michele Grieco Eerika Vuorio Mikko Tikkanen Sari Järvi Eva‐Mari Aro 《The Plant journal : for cell and molecular biology》2015,84(2):360-373
Thylakoid energy metabolism is crucial for plant growth, development and acclimation. Non‐appressed thylakoids harbor several high molecular mass pigment–protein megacomplexes that have flexible compositions depending upon the environmental cues. This composition is important for dynamic energy balancing in photosystems (PS) I and II. We analysed the megacomplexes of Arabidopsis wild type (WT) plants and of several thylakoid regulatory mutants. The stn7 mutant, which is defective in phosphorylation of the light‐harvesting complex (LHC) II, possessed a megacomplex composition that was strikingly different from that of the WT. Of the nine megacomplexes in total for the non‐appressed thylakoids, the largest megacomplex in particular was less abundant in the stn7 mutant under standard growth conditions. This megacomplex contains both PSI and PSII and was recently shown to allow energy spillover between PSII and PSI (Nat. Commun., 6, 2015, 6675). The dynamics of the megacomplex composition was addressed by exposing plants to different light conditions prior to thylakoid isolation. The megacomplex pattern in the WT was highly dynamic. Under darkness or far red light it showed low levels of LHCII phosphorylation and resembled the stn7 pattern; under low light, which triggers LHCII phosphorylation, it resembled that of the tap38/pph1 phosphatase mutant. In contrast, solubilization of the entire thylakoid network with dodecyl maltoside, which efficiently solubilizes pigment–protein complexes from all thylakoid compartments, revealed that the pigment–protein composition remained stable despite the changing light conditions or mutations that affected LHCII (de)phosphorylation. We conclude that the composition of pigment–protein megacomplexes specifically in non‐appressed thylakoids undergoes redox‐dependent changes, thus facilitating maintenance of the excitation balance between the two photosystems upon changes in light conditions. 相似文献
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17.
Noelia Lander Miguel A. Chiurillo Roberto Docampo 《The Journal of eukaryotic microbiology》2016,63(5):679-690
Genome editing by CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 (CRISPR‐associated gene 9) system has been transformative in biology. Originally discovered as an adaptive prokaryotic immune system, CRISPR/Cas9 has been repurposed for genome editing in a broad range of model organisms, from yeast to mammalian cells. Protist parasites are unicellular organisms producing important human diseases that affect millions of people around the world. For many of these diseases, such as malaria, Chagas disease, leishmaniasis and cryptosporidiosis, there are no effective treatments or vaccines available. The recent adaptation of the CRISPR/Cas9 technology to several protist models will be playing a key role in the functional study of their proteins, in the characterization of their metabolic pathways, and in the understanding of their biology, and will facilitate the search for new chemotherapeutic targets. In this work we review recent studies where the CRISPR/Cas9 system was adapted to protist parasites, particularly to Apicomplexans and trypanosomatids, emphasizing the different molecular strategies used for genome editing of each organism, as well as their advantages. We also discuss the potential usefulness of this technology in the green alga Chlamydomonas reinhardtii. 相似文献
18.
Yuki Watanabe Tarou Morikawa Takayuki Mine Yoshio Kawamura Gregory N. Nishihara Ryuta Terada 《Phycological Research》2017,65(4):265-271
The chronological change of photosynthetic efficiency in a frozen storage treatment of the Japanese Nori cultivation industry was examined in the cultivated red alga, Pyropia yezoensis f. narawaensis (Saga‐#5 Strain, Bangiales) by using pulse‐amplitude fluorometry. During the desiccation process that was conducted after the nursery cultivation season in November, the maximum quantum yield (F v/F m) of the gametophytic sporelings growing on the Nori‐net decreased monotonically with decreasing absolute water content (AWC), and was around 0.1 at 20% AWC. During frozen storage of the Nori‐net, the F v/F m of the frozen gametophyte was low but stable, and ranged between 0.10 ± 0.02 SD and 0.14 ± 0.05 SD. The magnitude of F v/F m for the gametophyte of the freezing treatment, after 10 min and 3 h of immersion in seawater, recovered quickly. After 10 min and 3 h of immersion, these values were 0.29 ± 0.12 SD and 0.47 ± 0.05 SD during the 14 days of freezing treatment, and 0.15 ± 0.02 SD and 0.29 ± 0.04 SD after 71 days of freezing treatment, and suggest that the ability to recover gradually decreased as the storage duration increased. The response of F v/F m from general cultivation (i.e., directly cultivated from the nursery cultivation season) and those after 47 days of freezing were almost identical, suggesting that the current Nori ‐net frozen storage period (6 or 7 weeks) was not detrimental to the gametophyte. 相似文献
19.
Gerotto C Alboresi A Giacometti GM Bassi R Morosinotto T 《Plant, cell & environment》2011,34(6):922-932
Photosynthetic organisms respond to strong illumination by activating several photoprotection mechanisms. One of them, non-photochemical quenching (NPQ), consists in the thermal dissipation of energy absorbed in excess. In vascular plants NPQ relies on the activity of PSBS, whereas in the green algae Chlamydomonas reinhardtii it requires a different protein, LHCSR. The moss Physcomitrella patens is the only known organism in which both proteins are present and active in triggering NPQ, making this organism particularly interesting for the characterization of this protection mechanism. We analysed the acclimation of Physcomitrella to high light and low temperature, finding that these conditions induce an increase in NPQ correlated to overexpression of both PSBS and LHCSR. Mutants depleted of PSBS and/or LHCSR showed that modulation of their accumulation indeed determines NPQ amplitude. All mutants with impaired NPQ also showed enhanced photosensitivity when exposed to high light or low temperature, indicating that in this moss the fast-responding NPQ mechanism is also involved in long-term acclimation. 相似文献
20.
Chlorophyll fluorescence has been often used as an intrinsic optical molecular probe to study photosynthesis. In this study, the origin of bands at 437 and 475.5 nm in the chlorophyll fluorescence excitation spectrum for emission at 685 nm in Arabidopsis chloroplasts was investigated using various optical analysis methods. The results revealed that this fluorescence excitation spectrum was related to the absorption characteristics of pigment molecules in PSII complexes. Moreover, the excitation band centred at 475.5 nm had a blue shift, but the excitation band at 437 nm changed relatively less due to induction of non‐photochemical quenching (NPQ). Furthermore, fluorescence emission spectra showed that this blue shift occurred when excitation energy transfer from both chlorophyll b (Chl b) and carotenoids (Cars) to chlorophyll a (Chl a) was blocked. These results demonstrate that the excitation band at 437 nm was mainly contributed by Chl a, while the excitation band at 475.5 nm was mainly contributed by Chl b and Cars. The chlorophyll fluorescence excitation spectrum, therefore, could serve as a useful tool to describe specific characteristics of light absorption and energy transfer between light‐harvesting pigments. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献