Project description:Regulation of expression of genes encoding chloroplast components is critical to the autotrophic plant and never more so than in the cotyledons of the de-etiolating seedling. Many chloroplast proteins are nuclear-encoded and a retrograde signal from the chloroplasts (the Plastid Signal) modulates nuclear transcription. However, not all chloroplast-targeted genes are subject to this control and not all plastid-dependent nuclear genes are chloroplast-targeted. We therefore aim to provide the most comprehensive screen yet of which genes are affected by plastid-signalling. To specifically knock-out positive plastid signalling in light-grown cotyledons, the herbicide Norflurazon (NF) is supplied in the growth medium, causing a carotenoid deficiency that leaves the chloroplasts vulnerable to photobleaching. This blocks the expression of a subset of nuclear genes, such as Lhcb and HEMA1. Two pairs of RNAs will directly compare the transcription in seedlings grown under continuous white light with and without NF. A third RNA will also be compared from a mutant that shows a degree of constitutive positive plastid signalling. These two mutants act synergistically to counteract the effect of NF on nuclear transcription. The gun1,gun5 double mutant maintains a significantly higher level of Lhcb and HEMA1 expression in the presence of photobeached chloroplasts than the NF-treated wild-type. This transcriptome set will therefore complement RNA1 (wild-type+NF) and indicate which of the genes identified from the RNA1/RNA2 comparison are subject to the particular gun1/gun5 plastid signalling pathway(s). The growth of conditions of the seedlings (namely on MS medium supplemented with 1.5% sucrose, for 3 days under continuous WL following 2 days germination in darkness) has been chosen from the results of our own recent studies using Northern blotting techniques that show these conditions to maximise the respective NF and gun mutant effects on Lhcb and HEMA1 gene expression. This experiment is part one of a two-part study to compare the transcriptional output of this NF-affected pathway with that of a newly discovered FR-mediated pathway. A subsequent array experiment will assess the nuclear response as affected by this FR/ phyA-input pathway and the two sets of array data will be compared and contrasted. Note: Col-0 wild-type (NASC code N1092). gun1,gun5 double mutant(obtained from Enriquez Lopez-Juez, Royal Holloway, University of London.(Mochizuki et al. 2001 PNAS 98: 2053-2058). This line cannot be donated by us as it is the IP of Joanne Chory (SALK Institute, USA). Treatment = a herbicide (Norflurazon) application which leads to chloroplast photobleaching and hence down regulation of nuclear genes dependent on plastid signalling from intact chloroplasts.

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)

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

Project description:Background: The Arabidopsis ANR1 gene is a key regulator of root architecture (Zhang and Forde, 1998): when ANR1 is down-regulated (by antisense or co-suppression) the resulting lines are no longer able to proliferate their lateral roots in response to localised supplies of NO3- (Zhang and Forde, 1998). ANR1 encodes a root-specific member of the MADS box family of transcription factors and is thought to be a component of a signalling pathway that links an external NO3- signal to increased meristematic activity in the lateral root meristem (Zhang et al., 1999).A major goal of our present BBSRC-funded project is to learn more about this NO3- response pathway by identifying the downstream targets of ANR1. To this end we have generated a set of transgenic lines in which ANR1 is under a novel post-translational control. This was achieved by tagging ANR1 with the steroid-binding domain of the rat glucocorticoid receptor (rGR) and expressing the fusion protein under the control of the CaMV 35S promoter. Initial results with these lines confirm that the architecture of the root system is altered in a way that correlates with the presence of the steroid inducer (dexamethasone, or DEX) and the expression of the ANR1::rGR transgene. We now wish to apply transcript analysis to one of these lines (ANGR4-12) to identify the genes whose expression is up- or down-regulated by ANR1. Sablowski and Meyerowitz (1998) successfully used an analogous approach to identify a gene that is an immediate target of the AP3 MADS-box transcription factor (although here, in the absence of microarray technology, differential display was used). Experimental: Plants of the two genotypes (ANGR4-12 and wild type) will be grown in sterile liquid culture for 3-4 weeks and then starved of N for 3 d (to quench the endogenous NO3- signalling pathway) before starting the DEX treatment. Roots will be harvested after 60 min from roots of DEX-treated and mock-treated RGR4-12 and control plants (four RNA samples). To minimise background noise due to environmental variables we will repeat the experiment three times and pool the RNA samples.

Project description:Aim: To identify regulatory factors that control: (1) chloroplast protein importand (2) chloroplast-to-nucleus signalling. This project is a joint proposal from the Jarvis lab which is interested in chloroplast protein import [1] and the Moller lab which is interested in plastid-to-nucleus signalling [2]. Background: The majority of chloroplast proteins are encoded in the nucleus and imported post-translationally into chloroplasts. The abundance of chloroplast proteins may therefore be regulated at multiple levels. It is well documented that the nuclear gene expression is responsive to (largely unknown) signals from the chloroplast [23] and evidence is now emerging that protein import is also a regulated process [1]. Protein import into chloroplasts is mediated by protein complexes in the outer and inner envelope membranes called Toc and Tic respectively. Biochemical studies of pea chloroplasts identified several Toc/Tic components. These proteins are mechanistic or structural components of the import apparatus. Arabidopsis homologues of the pea Toc/Tic proteins were identified by the AGI. Pea Toc34 is represented in Arabidopsis by two genes "Toc33 and Toc34" and pea Toc75 is represented by three genes. These different Tocs have different expression patterns and are proposed to have different precursor protein recognition specificities. The factors that regulate Toc expression in concert with the needs of plastids in developmentally different cells are unknown. Proposal: Two Arabidopsis mutants will be analysed. The ppi1 mutant is null for the putative precursor protein receptor Toc33 [1]and the ppi3 mutant is null for a putative component of the protein import channel Toc75-IV (on chromosome IV). ppi1 plants are yellow-green in appearance but remarkably healthy and grow only slightly more slowly than wild type. By contrast ppi3 plants are indistinguishable from wild type by eye although analysis of the mutant's chloroplast proteome is beginning to reveal some differences (K. Lilley personal communication). Gene expression changes in ppi1 are likely to be quite extensive. Retardation of chloroplast development in ppi1 will activate retrograde signalling pathways so that many nuclear photosynthetic genes are down-regulated. Changes in the expression of photosynthetic genes and of the genes responsible for mediating these responses may therefore be observed. Any regulatory and signalling genes identified will be of interest to the Moller lab. The expression of factors that regulate Toc/Tic gene expression may also be altered in ppi1. It should be possible to distinguish these factors from those involved in the general control of chloroplast gene expression by comparing the results from the two mutants. Genes affected in both mutants are more likely to be involved in regulating chloroplast import since it is unlikely that widespread changes in gene expression will be observed in ppi3. Changes in the expression of factors that regulate import post-translationallyand of the Toc/Tic genes themselves (many are on the RNA) may also be observed. References: 1. Jarvis P. et al. (1998) Science 282: 100-103. 2. Moller S.G. et al. (2001) Genes Dev. 15:90-103. 3. Jarvis P. (2001) Curr. Biol. 11: R307-R310.

Project description:Plants that exhibit secondary growth, such as trees, are a prominent feature of terrestrial ecosystems. Furthermore, secondary growth itself, particularly wood, has huge economic value. Despite the importance of secondary growth from both basic and applied science perspectives, little is known about the molecular mechanisms that underpin this facet of plant development. The proposed microarray experiments are designed to expand our knowledge of the regulation of secondary growth by combining the power of Arabidopsis genetics with complete transcriptome analysis. It is now well established that Arabidopsis can be grown under conditions that induce secondary growth in the hypocotyl, albeit small, wood. We have grown 8500 Arabidopsis plants of different genotypes under these conditions and will extract RNA from the developing vascular cambia of these plants to subject them to complete transcriptome analysis.The mutants that we have chosen for these analyses are all related to each other on the basis of the fact that they impact dormancy in either seeds or shoots (abi1, aba1, max4, axr1, AtMYB61 knockout, AtMYB50 knockout). The mutants themselves are the core group of mutants that are the focus of a three laboratory consortium, funded under the BBSRC Exploiting Genomics Initiative, to investigate the molecular basis of meristem dormancy in Arabidopsis. The other partners in the consortium are Dr. Ottoline Leyser (York) and Dr. Michael Holdsworth (IACR). While the Leyser and Holdsworth groups have investigated the impact of these mutations on transcriptome activity in shoot meristems and seeds respectively, our work focuses on the vascular cambium. Thus, this work will not only provide insights into the regulation of cambial function, but, when compared with the existing datasets from the Leyser and Holdworth labs, the work should also provide insights into the relationship between dormancy-impacted phenomena in different meristematic regions. Beyond this, the specific work on the cambium-specific regulation of genes in the MYB61KO will provide even greater insights into the functioning of this important resource allocation regulator, as it will build on a significant complete transcriptome dataset that is already available through GARNet. In total, the proposed analyses will generate important new data that builds on existing datasets, to provide an even more comprehensive understanding of gene function, and genetic networks, in an important biological and applied context. Please note that the sample numbers that we have provided below are meant to be the 'base' number for each biological condition (mutant, etc.), and that there will be independent TRIPLICATE biological replicates produced for each condition. (ie. A-1 to A-12). Experiment Overall Design: Number of plants pooled:200-400 per RNA sample

Project description:Background: The Arabidopsis ANR1 gene is a key regulator of root architecture (Zhang and Forde, 1998): when ANR1 is down-regulated (by antisense or co-suppression) the resulting lines are no longer able to proliferate their lateral roots in response to localised supplies of NO3- (Zhang and Forde, 1998). ANR1 encodes a root-specific member of the MADS box family of transcription factors and is thought to be a component of a signalling pathway that links an external NO3- signal to increased meristematic activity in the lateral root meristem (Zhang et al., 1999).A major goal of our present BBSRC-funded project is to learn more about this NO3- response pathway by identifying the downstream targets of ANR1. To this end we have generated a set of transgenic lines in which ANR1 is under a novel post-translational control. This was achieved by tagging ANR1 with the steroid-binding domain of the rat glucocorticoid receptor (rGR) and expressing the fusion protein under the control of the CaMV 35S promoter. Initial results with these lines confirm that the architecture of the root system is altered in a way that correlates with the presence of the steroid inducer (dexamethasone, or DEX) and the expression of the ANR1::rGR transgene. We now wish to apply transcript analysis to one of these lines (ANGR4-12) to identify the genes whose expression is up- or down-regulated by ANR1. Sablowski and Meyerowitz (1998) successfully used an analogous approach to identify a gene that is an immediate target of the AP3 MADS-box transcription factor (although here, in the absence of microarray technology, differential display was used). Experimental: Plants of the two genotypes (ANGR4-12 and wild type) will be grown in sterile liquid culture for 3-4 weeks and then starved of N for 3 d (to quench the endogenous NO3- signalling pathway) before starting the DEX treatment. Roots will be harvested after 60 min from roots of DEX-treated and mock-treated RGR4-12 and control plants (four RNA samples). To minimise background noise due to environmental variables we will repeat the experiment three times and pool the RNA samples. Experiment Overall Design: Number of plants pooled:20 Experiment Overall Design: Biological replicates: 2

Project description:Aim: To identify regulatory factors that control: (1) chloroplast protein importand (2) chloroplast-to-nucleus signalling. This project is a joint proposal from the Jarvis lab which is interested in chloroplast protein import [1] and the Moller lab which is interested in plastid-to-nucleus signalling [2]. Background: The majority of chloroplast proteins are encoded in the nucleus and imported post-translationally into chloroplasts. The abundance of chloroplast proteins may therefore be regulated at multiple levels. It is well documented that the nuclear gene expression is responsive to (largely unknown) signals from the chloroplast [23] and evidence is now emerging that protein import is also a regulated process [1]. Protein import into chloroplasts is mediated by protein complexes in the outer and inner envelope membranes called Toc and Tic respectively. Biochemical studies of pea chloroplasts identified several Toc/Tic components. These proteins are mechanistic or structural components of the import apparatus. Arabidopsis homologues of the pea Toc/Tic proteins were identified by the AGI. Pea Toc34 is represented in Arabidopsis by two genes "Toc33 and Toc34" and pea Toc75 is represented by three genes. These different Tocs have different expression patterns and are proposed to have different precursor protein recognition specificities. The factors that regulate Toc expression in concert with the needs of plastids in developmentally different cells are unknown. Proposal: Two Arabidopsis mutants will be analysed. The ppi1 mutant is null for the putative precursor protein receptor Toc33 [1]and the ppi3 mutant is null for a putative component of the protein import channel Toc75-IV (on chromosome IV). ppi1 plants are yellow-green in appearance but remarkably healthy and grow only slightly more slowly than wild type. By contrast ppi3 plants are indistinguishable from wild type by eye although analysis of the mutant's chloroplast proteome is beginning to reveal some differences (K. Lilley personal communication). Gene expression changes in ppi1 are likely to be quite extensive. Retardation of chloroplast development in ppi1 will activate retrograde signalling pathways so that many nuclear photosynthetic genes are down-regulated. Changes in the expression of photosynthetic genes and of the genes responsible for mediating these responses may therefore be observed. Any regulatory and signalling genes identified will be of interest to the Moller lab. The expression of factors that regulate Toc/Tic gene expression may also be altered in ppi1. It should be possible to distinguish these factors from those involved in the general control of chloroplast gene expression by comparing the results from the two mutants. Genes affected in both mutants are more likely to be involved in regulating chloroplast import since it is unlikely that widespread changes in gene expression will be observed in ppi3. Changes in the expression of factors that regulate import post-translationallyand of the Toc/Tic genes themselves (many are on the RNA) may also be observed. References: 1. Jarvis P. et al. (1998) Science 282: 100-103. 2. Moller S.G. et al. (2001) Genes Dev. 15:90-103. 3. Jarvis P. (2001) Curr. Biol. 11: R307-R310. Experiment Overall Design: Number of plants pooled:

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Transcription profiling of Arabidopsis irradated with cFR (far-red) light for 18 hr and treated with 20 nM of flumioxazin

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