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:In this experiment we used leaves from 6-week-old Arabidopsis SDH1-1/sdh1-1 mutant and Wt plants (Ws). The leaves were collected in the middle of light period.
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
Project description:Plant hypocotyls elongate in response to darkness. The response to darkness is gated by the circadian clock, such that wild-type plants (Col) only respond to darkness with growth once every 24 hours, whereas arrhythmic lines, such as CCA1-34, will respond to darkness with growth at any time of day. The experiment here was designed to find genes whose expression was correlated with growth. It should also pick up other genes that are gated by the circadian clock or that are direct targets of CCA1. Experiment Overall Design: Two genotypes were uses, wild-type (Col) and the arrhythmic CCA1-34 line that overexpresses the CCA1 protein. Plants were entrained in short day conditions for four days and then subjected light/dark pulses consisting of 160 minutes of light and 320 minutes of dark. We collected samples 120 minutes into the first and last dark periods of the day, corresponding to 280 and 1240 minutes after dawn. At the 280 minute time point Col plants are growing in response to darkness. At the 1240 minute time point Col plants are not growing. CCA1-34 plants are growing at both time points. The collection regime was continued for three days for a total of three temporal replicates for each time point/genotype combination.
2008-06-15 | E-GEOD-6906 | biostudies-arrayexpress
Project description:This experiment was a time course performed over 24 hours to look at the effects on gene expression of exposure to low red:far-red ratio light in Arabidopsis thaliana plants. In this way genes involved in the shade avoidance response might be identified. This experiment was designed for gene identification only and containes no replicates,genes identified were verified by quantitative PCR for publication.
2013-01-30 | E-MEXP-34 | biostudies-arrayexpress
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2019-07-17 | PXD005600 | Pride