Acclimation of photosynthesis to changes in the environment results decreases oxidative stress in Arabidopsis thaliana
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ABSTRACT:
ORGANISM(S): Arabidopsis thaliana
SUBMITTER: Leo Zeef
PROVIDER: E-MTAB-10282 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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Project description:Ascorbate (vitamin C) is an important antioxidant in leaves with multiple functions in photosynthesis and its levels are tightly regulated by light quality. The majority of work to date has focussed on regulation of ascorbate levels via biosynthesis. However, the pathway of ascorbate degradation, which is localised in the apoplast may additionally play a significant role. The degradative pathway begins with ascorbate oxidation by the enzyme ascorbate oxidase (AO) and hence we have examined the impact of manipulation of ascorbate oxidase activity on the content of ascorbate and the acclimation of photosynthesis to changing light levels. Leaf ascorbate content was highly light dependent in Nicotiana tobaccum being double in high compared with low light conditions. In contrast ascorbate oxidase activity was not altered by changing light levels. Transgenic tobacco lines with reduced or enhanced AO activity exhibited no morphological phenotype and photosynthesis under high light was similarly impaired irrespective of the measured AO activity. However further investigation between AO activity and leaf acclimation to changing light intensity revealed a suite of metabolic and transcriptome changes indicating a role for the apoplastic ascorbate pool in chloroplast to nucleus communication. In all genotypes, transcripts associated with ascorbate synthesis and recycling were less abundant following transition from high to low light. However transcripts associated with glutathione recycling, light harvesting, reaction centre function and the Calvin cycle were all increased in abundance. Following the transition from high to low light increases in leaf threonate, an ascorbate degradation product, were proportional to AO activity. A number of chloroplast synthesised amino acids were significantly increased both during high light and following transfer back to LL for 12 h. Similarly, several primary carbohydrates and TCA intermediates were significantly enhanced following high light treatment. In addition to light effects, AO activity had a significant impact on ï¢-alanine, aspartate and threonine. Intriguingly, a large number of fatty acids were reduced in antisense AO and wild-type plants immediately after high light stress however the content of these compounds were significantly increased in overexpressing sense lines. We conclude that AO mediated turnover plays an important role in adjusting cellular ascorbate content to photosynthetic need in a fluctuating light environment and that light mediated signals rapidly adjust that the apoplastic ascorbate pool.
2017-03-01 | E-MTAB-4816 | biostudies-arrayexpress
Project description:Photosynthetic diatoms are exposed to rapid and unpredictable changes in irradiance and spectral quality, and must be able to adapt their light harvesting systems to varying light conditions. Molecular mechanisms behind light acclimation in diatoms are largely unknown. We set out to investigate the mechanisms of high light acclimation in Phaeodactylum tricornutum using an integrated approach involving global transcriptional profiling, metabolite profiling and variable fluorescence technique. Algae cultures were acclimated to low light (LL), after which the cultures were transferred to high light (HL). Molecular, metabolic and physiological responses were studied at time points 0.5 h, 3 h, 6 h, 12 h, 24 h and 48 h after transfer to HL conditions. The integrated results indicate that the acclimation mechanisms in diatoms can be divided into an initial response phase (0.5 h), an intermediate acclimation phase (3-12 h) and a late acclimation phase (12-48 h). The initial phase is recognized by strong and rapid regulation of genes encoding proteins involved in photosynthesis, pigment metabolism and reactive oxygen species (ROS) scavenging systems. A significant increase in light protecting metabolites occur together with the induction of transcriptional processes involved in protection of cellular structures at this early phase. During the following phases, the metabolite profiling display a pronounced decrease in light harvesting pigments, whereas the variable fluorescence measurements show that the photosynthetic capacity increases strongly during the late acclimation phase. We show that P. tricornutum is capable of swift and efficient execution of photoprotective mechanisms, followed by changes in the composition of the photosynthetic machinery that enable the diatoms to utilize the excess energy available in HL. Central molecular players in light protection and acclimation to high irradiances have been identified. The experiment was designed as a time series, with diatom cultures were harvested at time points 0.5 h, 3 h, 6 h, 12 h, 24 h and 48 h after transfer to high light conditions. The reference samples were kept at low light and harvested in parallel with the treated samples. Three biological replicates were harvested for all samples.
2009-11-05 | E-GEOD-17237 | biostudies-arrayexpress
Project description:Plant thylakoid membranes contain hundreds of proteins closely interplaying to cope with ever-changing environmental conditions. We investigated how P. sativum (pea) grown at different irradiances optimizes light-use efficiency through the differential accumulation of thylakoid proteins. Thylakoid membranes from plants grown under limiting (LL), normal (NL) and high (HL) light intensity were characterized by combining chlorophyll fluorescence measurements with quantitative proteomic analysis. Protein sequences retrieved from available transcriptomic data considerably improved the protein profiling. We found that increasing growth irradiance affects the electron transport kinetics but not Photosystem (PS) I and II relative abundance. Two acclimation strategies were evident comparing plants acclimated to LL with higher irradiances: 1) in NL, plants turn on photoprotective responses mostly regulating the PSII light-harvesting capacity either accumulating Lhcb4.3 or favouring the xanthophyll cycle; 2) in HL, plants reduce the LHCII pool and enhance the PSII repair cycle. At increasing growth irradiance, plants increase the accumulation of ATP synthase and boost the electron transport to finely tune the ΔpH across the membrane and adjust the thylakoid architecture to optimize protein trafficking. Our results provide a quantitative snapshot on how plants coordinate light-harvesting, electron transport and protein synthesis adjusting the thylakoid membrane proteome in a light-dependent manner
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2010-12-31 | E-MEXP-2992 | biostudies-arrayexpress
Project description:In dense plant stands, the ratio between red and far-red (R:FR) light declines and shade intolerant species will respond to this cue for future shade by inducing the shade avoidance syndrome (SAS), enabling them to outgrow their neighbours. Shade tolerant species from the forest understory are unable to outgrow neighbouring trees and will suppress SAS. Although the molecular mechanisms underlying SAS are well studied in various species, mechanisms of SAS-suppression in shade tolerant species have rarely been studied. We applied RNA sequencing on Geranium pyrenaicum and G. robertianum, two wild species with contrasting growth responses to low R:FR light. G. pyrenaicum strongly induces petiole elongation when exposed to low R:FR light, at any time of the photoperiod. Contrastingly, G. robertianum only induces this response early in the day, and suppresses petiole growth in low R:FR light at the end of the photoperiod, which results after 24 hours in a net difference with control treatments of zero. We compared expression patterns in the most apical (most responsive) part of the second petioles, in two-week-old Geranium plants (two leaf stage) after 2 and 11.5 hours of far-red light enrichment. This way, we identified a number of novel candidate regulators of shade avoidance, and differential phytochrome control of plant immunity genes in the two species. For de-novo assembly of the reference transcriptomes, we pooled petiole- and leaf lamina tissue exposed to normal white light (180 mol m-2 s-1 PAR, R:FR 1.8, ± 60 mol m-2 s-1 blue light), low R:FR light (0.2), blue-depleted light (± 4 mol m-2 s-1 blue) and green shade (50 mol m-2 s-1 PAR, R:FR 0.45, ± 13 mol m-2 s-1 blue) for 2, 11.5 and 24 hours. Libraries of these samples were normalized, Illumina sequenced, and together with sequences of non-normalized petiole samples of the expression analysis constructed into a reference transcriptome for each species, using the Trinity protocol. Transcripts were clustered into orthologue clusters using the ortho-MCL clustering technique. Non-normalized libraries of samples (control vs. low R:FR light, 2 and 11.5 hours after start of the treatment) were sequenced and aligned to the newly assembled transcriptomes. Read counts were summed per orthologue cluster before statistical analysis was proceeded.
2017-02-01 | E-MTAB-5371 | biostudies-arrayexpress
Project description:affy_genomic_poplar - affy_genomic_poplar - The project aims to identify genes of interest for water deficit acclimation in poplar. We look for genes and gene expression networks related to drought stress in two hybrid cultivars, differing in their drought tolerance in field. Affymetrix poplar genome array was designed on several Populus species. In order to deal with comparative approaches, we checked the convenience of the array by hybridizing genomic DNA of the two hybrid cultivars (Populus deltoides × Populus nigra, namely ‘cv Carpaccio’ and ‘cv Soligo’). This point is important as transcript sequence might have diverged in the two genomes (Fossati et al, 2005), which could lead to absence of hybridization without physiological meaning. -Two poplar cultivars, Soligo (S) and Carpacio (C) were grown in controlled conditions. Mature leaves were collected and genomic DNA was extracted from leaves in CTAB buffer. gDNA was fragmented with DNAse1. DNA fragments were labelled with Biotin N6-ddATP and hybridized on Affymetrix poplar genome array. Two technical replicates per genotype were performed. Keywords: genomic comparison,gain of fuction epimutation 4 arrays - poplar
2011-04-01 | E-GEOD-21334 | biostudies-arrayexpress
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2008-06-15 | E-GEOD-6906 | biostudies-arrayexpress