Phytochrome Interacting Factor 4 and 5 regulate different set of genes in high and low red/far-red light
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ABSTRACT: As sessile organisms plants developed a veriety of adaptive responses to the ever changing environment. One of these responses is the shade avoidance syndrome which is composed of different responses like elongation growth, hyponastic leafs or early flowering to shade (low R/FR). Phytochrcome Interacting Factor 4 and 5 are bHLH transcription factors reported to activate gene expression upon perception of low R/FR. Using this miroarray experiment we identified new genes regulated by PIF4 and PIF5 in response to shade and investigated their genome wide role.
Project description:As sessile organisms plants developed a veriety of adaptive responses to the ever changing environment. One of these responses is the shade avoidance syndrome which is composed of different responses like elongation growth, hyponastic leafs or early flowering to shade (low R/FR). Phytochrcome Interacting Factor 4 and 5 are bHLH transcription factors reported to activate gene expression upon perception of low R/FR. Using this miroarray experiment we identified new genes regulated by PIF4 and PIF5 in response to shade and investigated their genome wide role. Here pif4pif5 double mutant, pif5 single mutant and PIF5 overexpressing line were compared to Col-0 wild type A. thaliana plants when grown under 12:12 DL circles for 14 days in high R/FR and either kept in high R/FR or transferred to low R/FR for additional 2 hours
Project description:Phytochromes are red/far red photosensors regulating numerous developmental programs in plants. Among them phytochrome A (phyA) is essential to enable seedling de-etiolation in continuous far-red (FR) light a condition mimicking the environment under a dense canopy. The ecological relevance of this response is demonstrated by the high mortality rate of phyA mutants germinating in deep vegetational shade. phyA signaling involves a direct interaction of the photoreceptor with members of the bHLH transcription factor family, PIF1 and PIF3 (Phytochrome Interacting Factor). Here we investigated the involvement of PIF4 and PIF5 in phyA signaling and found that they redundantly control de-etiolation in FR light. The pif4pif5 double mutant is hypersensitive to low fluence rates of FR light. This phenotype is dependent on FR light perception by phyA but does not rely on alterations of the phyA level. Our microarrays analysis shows that PIF4 and PIF5 are part of an inhibitory mechanism repressing the expression of some light-responsive genes in the dark and are also needed for full expression of several growth-related genes in the light. Unlike PIF1 and PIF3, PIF4 and PIF5 are not degraded in response to FR light indicating that they are light-regulated by a different mechanism. Our genetic analysis suggests that this is achieved through the sequestration of these PIFs by the closely related bHLH transcription factor HFR1 (long Hypocotyl in FR light).
Project description:Phytochromes are red/far red photosensors regulating numerous developmental programs in plants. Among them phytochrome A (phyA) is essential to enable seedling de-etiolation in continuous far-red (FR) light a condition mimicking the environment under a dense canopy. The ecological relevance of this response is demonstrated by the high mortality rate of phyA mutants germinating in deep vegetational shade. phyA signaling involves a direct interaction of the photoreceptor with members of the bHLH transcription factor family, PIF1 and PIF3 (Phytochrome Interacting Factor). Here we investigated the involvement of PIF4 and PIF5 in phyA signaling and found that they redundantly control de-etiolation in FR light. The pif4pif5 double mutant is hypersensitive to low fluence rates of FR light. This phenotype is dependent on FR light perception by phyA but does not rely on alterations of the phyA level. Our microarrays analysis shows that PIF4 and PIF5 are part of an inhibitory mechanism repressing the expression of some light-responsive genes in the dark and are also needed for full expression of several growth-related genes in the light. Unlike PIF1 and PIF3, PIF4 and PIF5 are not degraded in response to FR light indicating that they are light-regulated by a different mechanism. Our genetic analysis suggests that this is achieved through the sequestration of these PIFs by the closely related bHLH transcription factor HFR1 (long Hypocotyl in FR light). Experiment Overall Design: he pif4pif5 double mutant were compared to wild-type plants when kept in the dark or subjected to 1 or 24 hours of 0.5 or 5 µmol/m2/s far-red light respectively.
Project description:Phytochrome Interacting Factor 5 plays an important role in adaptive responses of plants to shaded environment collectively called shade avoidance syndrome. PIF 5 belongs to the bHLH transcription factor family and regulated gene expression in a low R/FR dependent fashion. In this experiment we investigate PIF5-DNA-binding genome wide to generate a candidate list of genes, which are directly regulated by PIF5. ChIP-Seq sample of whole seedlings treated with low R/FR light
Project description:Phytochrome Interacting Factor 5 plays an important role in adaptive responses of plants to shaded environment collectively called shade avoidance syndrome. PIF 5 belongs to the bHLH transcription factor family and regulated gene expression in a low R/FR dependent fashion. In this experiment we investigate PIF5-DNA-binding genome wide to generate a candidate list of genes, which are directly regulated by PIF5.
Project description:Arabidopsis is a shade avioding plant. Under simulated shade light with reduced red-to-far red (R:FR) ratio around 0.7, hypocotyls of Arabidopsis seedlings elongate, which is one of the typical shade avoidance responses.We discovered that when the R:FR ratio further decreases to around 0.1 (strong shade), the shade-induced elongation of hypocotyl is abolished and phytochrome A (phyA) mediates this response.In this study, we aim to examine the difference between shade and strong shade treatment and uncover the role of phyA in regulating the shade avoidance responses.
Project description:In dense stands,the earliest neighbor response is induced by touching,leading to shade avoidance. During light competion the R:FR distribution is not homogenous, leading to local differences in light quality (R:FR) within the same leaf. Hyponasty is induced by FR-signaling in the lamina tip, which then induces local cell growth in the petiole base. Likewise, local touching of the leaf tip induces a similar phenoype. We studied gene expression in Arabidopsis, exposed to supplemental-FR in the lamina tip and in whole rosette plant. We harvested the lamina tip and the petiole base after 5h of the treatments (white-light, supplemeted-FR in the lamina tip (local FR) and rossete plants exposed to low R:FR (whole plant FR))
Project description:The goal of this work was to investigate the influence of low red to far-red (R:FR) signals generated by a biological weedy and an artificial source of far-red light on the nitrate assimilation pathway in maize. In the absence of direct resource competition, far-red light reflected from neighboring weeds compromises light quality (red to far-red ratio; R/FR) and causes a wide range of morphological and physiological responses at early growth stages of crop plants. This study has investigated the effects of low R/FR light signals on nitrate assimilation in maize seedlings. The transcript levels of genes, metabolites, and activities of enzyme in the nitrate assimilation pathway under a biological and a simulated low R:FR light environment were compared with a high R:FR control environment. Low R:FR signals stimulated nitrate accumulation in maize leaves, which did not appear to result from the upregulation of nitrate transporter genes. A significant reduction in ferredoxin-dependent glutamine:2-oxoglutarate aminotransferase activity appears to play a major role in nitrate accumulation under low R:FR light environments, while activities of other enzymes of the nitrate assimilation pathway remain unchanged.
Project description:We performed a transcriptome analysis of a 30 -hour infection time course aiming to unravel hormonal and metabolic pathways affected by FR which would in turn modulate disease resistance. Our data show that supplemental FR, received before pathogen inoculation, triggers the FR-induced susceptibility, which is associated with a delay in pathogen recognition and defense activation via JA and possibly ethylene signaling. The transcriptome analysis highlighted a set of six PROTEINASE INHIBITOR genes (PI) that are induced only in WL-treated samples. As PI genes are described to be JA-responsive genes, the FR-induced susceptibility in tomato is possibly due to a dampening of JA-mediated gene induction and expression affecting defense responses resulting in more susceptible plants.
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) Keywords: strain_or_line_design