Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

Transcription profiling time course experiment 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

ABSTRACT: 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.

ORGANISM(S): Arabidopsis thaliana

SUBMITTER: Michael Salter

PROVIDER: E-MEXP-34 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Gating of the rapid shade-avoidance response by the circadian clock in plants.

Salter Michael G MG Franklin Keara A KA Whitelam Garry C GC

Nature 20031201 6967

The phytochromes are a family of plant photoreceptor proteins that control several adaptive developmental strategies. For example, the phytochromes perceive far-red light (wavelengths between 700 and 800 nm) reflected or scattered from the leaves of nearby vegetation. This provides an early warning of potential shading, and triggers a series of 'shade-avoidance' responses, such as a rapid increase in elongation, by which the plant attempts to overgrow its neighbours. Other, less immediate, respo ...[more]

PMID: 14668869

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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, Â± 60 mol m-2 s-1 blue light), low R:FR light (0.2), blue-depleted light (Â± 4 mol m-2 s-1 blue) and green shade (50 mol m-2 s-1 PAR, R:FR 0.45, Â± 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.

Project description:This application is the second part of a BBSRC-funded grant to compare and contrast the plastid-signalling pathways disrupted by Norflurazon and far-red light treatment of Arabidopsis seedlings. The first application of this laboratory to GARNet's Affymetrix service (2002-08-25-17.41.49_McCormac) addressed the Norflurazon pathway; this application addresses the far-red pathway. The assembly of photosynthetic complexes in developing chloroplasts is critical to the establishment of the autotrophic plant. This requires light-mediated upregulation of both nuclear- and chloroplast-encoded genes. The expression of such photosynthetically-associated nuclear genes is also often dependant on a retrograde plastid signal which emanates from chloroplasts to modulate nuclear transcription. Extensive studies using the herbicide Norflurazon to knock-out the plastid signal (including this lab's previous Affymetrix application to GARNet) are identifying the affected gene sets. However, genetic studies have indicated the existence of more than one plastid signalling pathway. We have recently investigated a phytochrome A-mediated, far-red (FR) input pathway which blocks subsequent chloroplast development under white light (WL). This has also been found to inhibit the transcription of a small group of known nuclear-encoded plastidic proteins. Here we wish to establish how wide-reaching this FR-effect is on nuclear transcription, and will directly compare the affected gene groups with those identified from our earlier (and other's) studies with a Norflurazon treatment. In this array experiment we will compare RNA from seedlings grown in complete darkness (D) before transfer to WL, with that of seedlings preconditioned under a restricted wavelength FR source before exposure to WL. This comparison of FR- and Norflurazon-affected gene groupings will indicate whether the plastid signalling pathways are likely to be the same, overlapping or highly divergent. As well as wild-type seedlings, the gun1,gun5 mutant line is to be used as both these alleles are well established as alleviating the Norflurazon-inhibited pathway, but their affect on the FR-pathway is less clear. A single replicate of a phyA-null mutant line will also be included in order to differentiate between specific phytochromeA-mediated responses and other FR effects. It is envisaged that, in general, D- and FR-treated samples of the phyA mutant line will respond in the same way as each other and as the wild-type D-treated samples and, thus, the lack of a biological repeat in this case is not a major short-fall. The proposed experiment will consist of: wild-type: D-pretreated (x2 biological replicates) wild-type: FR-preconditioned (x2) gun1,gun5: D-pretreated (x2) gun1,gun5: FR-preconditioned (x2) phyA: D-pretreated (x1) phyA: FR-preconditioned (x1) Experiment Overall Design: Number of plants pooled:300 seedlings

Dataset Information

Transcription profiling time course experiment 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

Publications

Gating of the rapid shade-avoidance response by the circadian clock in plants.

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