Project description:For establishing the photosynthetic apparatus plant cells must orchestrate the expression of genes encoded in both nucleus and chloroplast. Therefore a crosstalk between the two compartments is necessary. We employed a gene expression profiling approach in order to elucidate the changes in gene expression that occur at different stages of plastid development.
Project description:Chloroplast biogenesis represents a crucial step in seedling development, and is essential for the transition to autotrophic growth in plants. This light-controlled process relies on the transcription of nuclear and plastid genomes that drives the effective assembly and regulation of the photosynthetic machinery. Here we reveal a novel regulation level for this process by showing the involvement of chromatin remodelling in the coordination of nuclear and plastid gene expression for proper chloroplast biogenesis and function. The two Arabidopsis homologs of the yeast EPL1 proteins, core components of the NuA4 histone acetyl-transferase complex, are essential for the correct assembly and performance of chloroplasts. EPL1 proteins are necessary for the coordinated expression of nuclear genes encoding most of the components of chloroplast transcriptional machinery, specifically promoting H4K5Ac deposition in these loci. These data unveil a key participation of epigenetic regulatory mechanisms in the coordinated expression of the nuclear and plastid genomes.
Project description:In response to environmental light signals, transcriptomic adjustment plays an important role in Arabidopsis seed germination and seedling development. G-box cis-element is commonly present in promoters of genes positively or negatively responding to the light signal. For the pursuit of additional transcriptional regulator modulating light-mediated transcriptome changes, we have identified AtbZIP16, a basic region/leucine zipper motif transcription factor, via G-box DNA affinity chromatography. We have confirmed that AtbZIP16 possesses G-box-specific binding activity. Analyses of atbzip16 mutants indicate that AtbZIP16 is a negative regulator in phyB-mediated inhibition of cell elongation, but a positive regulator in phytochrome-mediated seed germination process. Transcriptomic analysis supports that AtbZIP16 is primarily a transcriptional repressor regulating light-, GA- and ABA-responsive genes. Chromatin immunoprecipitation study revealed that AtbZIP16 could directly target RGL2, a DELLA gene, and indirectly repress the expression of PIL5 gene, which encodes a bHLH protein inhibiting seed germination in Arabidopsis. Our study indicated that, through repressing the expression of RGL2 and the antagonizing the expression of PIL5, AtbZIP16 functions to promote seed germination and hypocotyl elongation during early stages of Arabidopsis seedling development. In response to environmental light signals, transcriptomic adjustment plays an important role in Arabidopsis seed germination and seedling development. G-box cis-element is commonly present in promoters of genes positively or negatively responding to the light signal. For the pursuit of additional transcriptional regulator modulating light-mediated transcriptome changes, we have identified AtbZIP16, a basic region/leucine zipper motif transcription factor, via G-box DNA affinity chromatography. We have confirmed that AtbZIP16 possesses G-box-specific binding activity. Analyses of atbzip16 mutants indicate that AtbZIP16 is a negative regulator in phyB-mediated inhibition of cell elongation, but a positive regulator in phytochrome-mediated seed germination process. Transcriptomic analysis supports that AtbZIP16 is primarily a transcriptional repressor regulating light-, GA- and ABA-responsive genes. Chromatin immunoprecipitation study revealed that AtbZIP16 could directly target RGL2, a DELLA gene, and indirectly repress the expression of PIL5 gene, which encodes a bHLH protein inhibiting seed germination in Arabidopsis. Our study indicated that, through repressing the expression of RGL2 and the antagonizing the expression of PIL5, AtbZIP16 functions to promote seed germination and hypocotyl elongation during early stages of Arabidopsis seedling development.
Project description:Plastids emit signals that broadly affect cellular processes. Based on previous genetic analyses, we propose that plastid signaling regulates the downstream components of a light signaling network and that these interactions coordinate chloroplast biogenesis with both the light environment and development by regulating gene expression. We tested these ideas by analyzing light-regulated and plastid-regulated transcriptomes. We found that the plastid is a major regulator of light signaling, attenuating the expression of more than half of all light-regulated genes in our dataset and changing the nature of light regulation for a smaller fraction of these light-regulated genes. Our analyses provide evidence that light and plastid signaling are interactive processes and are consistent with these interactions serving as major drivers of chloroplast biogenesis and function.
Project description:Plastids emit signals that broadly affect cellular processes. Based on previous genetic analyses, we propose that plastid signaling regulates the downstream components of a light signaling network and that these interactions coordinate chloroplast biogenesis with both the light environment and development by regulating gene expression. We tested these ideas by analyzing light-regulated and plastid-regulated transcriptomes. We found that the plastid is a major regulator of light signaling, attenuating the expression of more than half of all light-regulated genes in our dataset and changing the nature of light regulation for a smaller fraction of these light-regulated genes. Our analyses provide evidence that light and plastid signaling are interactive processes and are consistent with these interactions serving as major drivers of chloroplast biogenesis and function. Four biological replicates were grown separately under the same conditions. Arabidopsis seedlings were grown in the presence (+Lin) or absence (-Lin) of lincomycin in 0.5 µmol m-2 s-1 blue plus red (BR) light for 6 days. After 6 days of growth in 0.5 µmol m-2 s-1 of BR light, seedlings were transferred to 60 µmol m-2 s-1 BR light. 50-100 seedlings were collected before (0 h) and 0.5 h, 1 h, 4 h, and 24 h after the 0.5 to 60 µmol m-2 s-1 BR-fluence-rate shift for RNA extraction and hybridization on Affymetrix microarrays.
Project description:Retrograde signaling from the chloroplast to the nucleus is necessary to regulate the chloroplast proteome during development and fluctuating environmental conditions. Although the specific chloroplast process(es) that must occur and the nature of the signal(s) that exits the chloroplast are not well understood, previous studies using drug inhibitors of chloroplast biogenesis have revealed that normal chloroplast development is required to express Photosynthesis Associated Nuclear Genes (PhANGs). In an attempt to determine which specific steps in chloroplast development are involved in retrograde signaling, we analyzed Arabidopsis mutants defective in the six genes encoding sigma factor (Sig) proteins that are utilized by the plastid-encoded RNA polymerase to transcribe specific sets of plastid genes. Here, we demonstrate that both Sig2 and Sig6 have partially redundant roles in not only plastid transcription, but also tetrapyrrole synthesis and retrograde signaling to control PhANG expression. Normal PhANG expression can be partly restored in the sig2 mutant by increasing heme synthesis. Furthermore, there is a genetic interaction between Sig and GUN (genomes uncoupled) genes to generate chloroplast-retrograde signals. These results demonstrate that defective plastid transcription is the source of at least two retrograde signals to the nucleus; one involving tetrapyrrole synthesis and the other involving the accumulation of an unknown plastid transcript. We also propose that the study of sig mutants (with defects in the expression of specific plastid genes) provides a new genetic system, which avoids the use of harsh inhibitors and their potential side effects, to monitor developmental retrograde signaling and to elucidate its mechanisms.
Project description:Zebra leaf is a special phenotype of variegated leaf in monocotyledonous plant. Here, we characterized a mutant zebra10 (zb10) in maize, which displays defective chloroplast development in white section of leaves at the seedling stage and pale-white kernels. Map based cloning revealed that ZB10 encodes plastid terminal oxidase (ZmPTOX) which is localized in chloroplasts. ZmPTOX protein is highest expressed in leaves and also highly expressed in endosperm. Expression and metabolism analysis showed that function-loss of PTOX interferes with carotenoid synthesis and chloroplast biogenesis by affecting phytoene desaturase activity. In-depth observation showed that crossband formation of zebra leaf could be related to photoperiodic rhythm, and expression of alternative oxidases 2 (ZmAOX2) could be regulated by circadian rhythm and light intensity in zb10. Further studies revealed ectopic expression of ZmAOX2 protein can function in chloroplasts and rescue the defective phenotype of im. We conclude that ZmPTOX plays an vital role in carotenoid synthesis and plastid biogenesis in maize. ZmAOX2 involve in formation of zebra crossbands with diurnal rhythm and green-revertible process of leaves in zb10.
Project description:four biological replicates of arabidopsis accession columbia 78h old whole seedling expression data Keywords: exon/intergenic comparison
Project description:In response to environmental light signals, transcriptomic adjustment plays an important role in Arabidopsis seed germination and seedling development. G-box cis-element is commonly present in promoters of genes positively or negatively responding to the light signal. For the pursuit of additional transcriptional regulator modulating light-mediated transcriptome changes, we have identified AtbZIP16, a basic region/leucine zipper motif transcription factor, via G-box DNA affinity chromatography. We have confirmed that AtbZIP16 possesses G-box-specific binding activity. Analyses of atbzip16 mutants indicate that AtbZIP16 is a negative regulator in phyB-mediated inhibition of cell elongation, but a positive regulator in phytochrome-mediated seed germination process. Transcriptomic analysis supports that AtbZIP16 is primarily a transcriptional repressor regulating light-, GA- and ABA-responsive genes. Chromatin immunoprecipitation study revealed that AtbZIP16 could directly target RGL2, a DELLA gene, and indirectly repress the expression of PIL5 gene, which encodes a bHLH protein inhibiting seed germination in Arabidopsis. Our study indicated that, through repressing the expression of RGL2 and the antagonizing the expression of PIL5, AtbZIP16 functions to promote seed germination and hypocotyl elongation during early stages of Arabidopsis seedling development. In response to environmental light signals, transcriptomic adjustment plays an important role in Arabidopsis seed germination and seedling development. G-box cis-element is commonly present in promoters of genes positively or negatively responding to the light signal. For the pursuit of additional transcriptional regulator modulating light-mediated transcriptome changes, we have identified AtbZIP16, a basic region/leucine zipper motif transcription factor, via G-box DNA affinity chromatography. We have confirmed that AtbZIP16 possesses G-box-specific binding activity. Analyses of atbzip16 mutants indicate that AtbZIP16 is a negative regulator in phyB-mediated inhibition of cell elongation, but a positive regulator in phytochrome-mediated seed germination process. Transcriptomic analysis supports that AtbZIP16 is primarily a transcriptional repressor regulating light-, GA- and ABA-responsive genes. Chromatin immunoprecipitation study revealed that AtbZIP16 could directly target RGL2, a DELLA gene, and indirectly repress the expression of PIL5 gene, which encodes a bHLH protein inhibiting seed germination in Arabidopsis. Our study indicated that, through repressing the expression of RGL2 and the antagonizing the expression of PIL5, AtbZIP16 functions to promote seed germination and hypocotyl elongation during early stages of Arabidopsis seedling development. Three biological replicates for 4-d-old seedlings grown under dark or red-light and long-day (0.5 ?mole m-2 sec-1) contitions.