Project description:Circadian clocks generate endogenous rhythms in most organisms from cyanobacteria to humans and facilitate entrainment to environmental diurnal cycles, thus conferring a fitness advantage. Both transcriptional and posttranslational mechanisms are prominent in the basic network architecture of circadian systems. Posttranscriptional regulation, including mRNA processing, is emerging as a critical step for the clock function. However, little is known about the molecular mechanisms linking RNA metabolism to the circadian clock network. Here we report that a conserved SNW/SKIP domain protein, SKIP, a splicing factor and component of the spliceosome, is involved in the posttranscriptional regulation of circadian clock genes in Arabidopsis. Mutation in SKIP lengthens the circadian period in a temperature sensitive manner, affects light input and the sensitivity of light resetting to the clock. SKIP physically interacts with the spliceosomal splicing factor SR45 and associates with the pre-mRNA of clock genes, such as PRR7 and PRR9, and is necessary for the regulation of their alternative splicing and mRNA maturation. Genome-wide investigations reveal that SKIP functions in regulating alternative splicing of many genes, presumably through modulating recognition or cleavage of 5' and 3' splicing site. Our study addresses a fundamental question on how the mRNA splicing machinery contributes to circadian clock functions at a posttranscriptional level. Our findings revealed that AtSKIP is a splicing factor and a component of spliceosome. To further investigate effects of mutation in SKIP on the genome-wide changes of alternative splicing, we performed ultra-highthroughput RNA sequencing, using 10-day old seedlings. Two biological replicates for both wild type (Col-0) and skip-2 were designed.
Project description:Circadian clocks generate endogenous rhythms in most organisms from cyanobacteria to humans and facilitate entrainment to environmental diurnal cycles, thus conferring a fitness advantage. Both transcriptional and posttranslational mechanisms are prominent in the basic network architecture of circadian systems. Posttranscriptional regulation, including mRNA processing, is emerging as a critical step for the clock function. However, little is known about the molecular mechanisms linking RNA metabolism to the circadian clock network. Here we report that a conserved SNW/SKIP domain protein, SKIP, a splicing factor and component of the spliceosome, is involved in the posttranscriptional regulation of circadian clock genes in Arabidopsis. Mutation in SKIP lengthens the circadian period in a temperature sensitive manner, affects light input and the sensitivity of light resetting to the clock. SKIP physically interacts with the spliceosomal splicing factor SR45 and associates with the pre-mRNA of clock genes, such as PRR7 and PRR9, and is necessary for the regulation of their alternative splicing and mRNA maturation. Genome-wide investigations reveal that SKIP functions in regulating alternative splicing of many genes, presumably through modulating recognition or cleavage of 5' and 3' splicing site. Our study addresses a fundamental question on how the mRNA splicing machinery contributes to circadian clock functions at a posttranscriptional level.
Project description:A better understanding of the mechanisms for plant in response to abiotic stresses is key for the improvement of plant to resistant to the stresses. Much has been known for the regulation of gene expression in response to salt stress at transcriptional level, however, little is known at posttranscriptional level for this response. Recently, we identified that SKIP is a component of spliceosome and is necessary for the regulation of alternative splicing and mRNA maturation of clock genes. In this study, we observed that skip-1 is hypersensitive to salt stress. SKIP is necessary for the alternative splicing and mRNA maturation of several salt tolerance genes, e.g. NHX1, CBL1, P5CS1, RCI2A, and PAT10. Genome-wide analysis reveals that SKIP mediates the alternative splicing of many genes under salt stress condition, most of the new alternative splicing events in skip-1 is intron retention, which leads to the premature termination codon in their mRNA. SKIP also controls the alternative splicing by modulating the recognition or cleavage of 5' and 3' splice donor and acceptor sites under salt stress condition. Therefore, this study addresses a fundamental question on how the mRNA splicing machinery contributes to salt response at a posttranscriptional level. Totally six samples, two treatments and two genotypes, and each have two replicats.
Project description:A better understanding of the mechanisms for plant in response to abiotic stresses is key for the improvement of plant to resistant to the stresses. Much has been known for the regulation of gene expression in response to salt stress at transcriptional level, however, little is known at posttranscriptional level for this response. Recently, we identified that SKIP is a component of spliceosome and is necessary for the regulation of alternative splicing and mRNA maturation of clock genes. In this study, we observed that skip-1 is hypersensitive to salt stress. SKIP is necessary for the alternative splicing and mRNA maturation of several salt tolerance genes, e.g. NHX1, CBL1, P5CS1, RCI2A, and PAT10. Genome-wide analysis reveals that SKIP mediates the alternative splicing of many genes under salt stress condition, most of the new alternative splicing events in skip-1 is intron retention, which leads to the premature termination codon in their mRNA. SKIP also controls the alternative splicing by modulating the recognition or cleavage of 5' and 3' splice donor and acceptor sites under salt stress condition. Therefore, this study addresses a fundamental question on how the mRNA splicing machinery contributes to salt response at a posttranscriptional level.
Project description:Study on differential gene expression and splicing between wildtype and clock mutants. This study is part of a comparative analysis of the role of Protein Methyltransferase 5 in the regulation of transcriptional and post-transcriptional processes simultaneously in Arabidopsis and Drosophila. Circadian rhythms allow organisms to time biological processes to the most appropriate phases of the day/night cycle1. Post-transcriptional regulation is emerging as an important component of circadian networks2-6, but the molecular mechanisms linking the circadian clock to the control of RNA processing are largely unknown. Here we show that Protein Arginine Methyl Transferase 5 (PRMT5), which transfers methyl groups to arginine residues present in histones7 and Sm spliceosomal proteins8,9, links the circadian clock to the control of alternative splicing in plants. Mutations in prmt5impair multiple circadian rhythms in Arabidopsis thaliana and this phenotype is caused, at least in part, by a strong alteration in alternative splicing of the core-clock gene PSEUDO RESPONSE REGULATOR 9 (PRR9). Furthermore, genome wide studies show that PRMT5 contributes to regulate many pre-mRNA splicing events most likely modulating 5´splice site (5´ss) recognition. PRMT5 expression shows daily and circadian oscillations, and this contributes to mediate the circadian regulation of expression and alternative splicing of a subset of genes. Circadian rhythms in locomotor activity are also disrupted in dart5, a mutant affected in the Drosophila melanogaster PRMT5 homolog, and this is associated with alterations in splicing of the core-clock gene period (per) and several clock associated genes. Our results reveal a key role for PRMT5 in the regulation of alternative splicing and indicate that the interplay between the circadian clock and the regulation of alternative splicing by PRMT5 constitutes a common mechanism that helps organisms to synchronize physiological processes with daily changes in environmental conditions.
Project description:Purpose: Circadian clock in plants temporally coordinates biological processes throughout the day synchronizing gene expression with environmental changes. Here, we examined the genome-wide circadian and diurnal control of Arabidopsis transcriptome using high throughout RNA-seq approach. Methods: Transcriptional and posttranscritional profiles were identified and characterized for Arabidopsis seedlings grown under continuous light or long-day condition (16 h light/8 h dark) for one day (each condition has two biological replicates). Results: We show that rhythmic posttranscriptional regulation is also a significant factor for genome-wide profile of circadian plant transcriptome. Two major posttranscriptioal mechanisms alternative splicing (AS) and alternative polyadenylation (APA) show circadian rhythmicity, resulting from the oscillation in the genes invovled in AS and APA. Conclusions: Arabidopsis circadian clock not only controls the transcription of genes, but also affects their posttranscriptional regulation through regulating AS and APA.
Project description:Alternative splicing plays a major role in expanding the potential informational content of eukaryotic genomes. It is an important post-transcriptional regulatory mechanism that can increase protein diversity and affect mRNA stability. Cold stress, which adversely affects plants growth and development, regulates the transcription and splicing of plants splicing factors. This affects the pre-mRNA processing of many genes. To identify cold regulated alternative splicing we applied Affymetrix Arabidopsis tiling arrays to survey the transcriptome under cold treatment conditions. Two-week old Arabidopsis seedlings grown on agar were subjected to 24 hours of cold (4°C) treatment under long day conditions. Control and cold-treated plants were harvested at the same time to ensure that observed differences would not be due to circadian clock effects on transcripts. Total RNA from four biological repeats were used for microarray hybridization.
Project description:Abscisic acid (ABA) plays a key role in plant development and responses to abiotic stress. A wide number of regulatory mechanisms on ABA perception and signaling are known, including transcriptional regulation and post-translational regulations; however, less to know about the post-transcriptional regulations. In this work, we have found that SKIP, a splicing factor in spliceosome, positively regulates ABA signal transduction. Mutation of SKIP, skip-1, confers ABA insensitive phenotype in seed germination, root growth, and ABA-responsive gene expression. Transformation of SKIP genomic DNA to skip-1 is able to recover its defects. SKIP binds to the pre-mRNA of genes in ABA signaling, such as PYL8, to regulate their splicing. The alternative splicing of PYL7, PYL8, ABF2, and ABI5 in ABA pathway is disrupted by skip-1, reducing the mRNA levels of them. The abnormal splicing of PP2Cs activates their transcription by skip-1, suggesting there is a feedback regulation for PP2Cs caused by skip-1. The down-regulation of PYL ABA receptors, ABF2 and ABI5 ABA response transcription factors, and the up-regulation of PP2Cs through alternative splicing reduce the plant responses to ABA in skip-1. SKIP is required for ABA-mediated genome-wide alternative splicing. ABA treatment enhances the novel splicing events in WT genome-widely. The novel alternative splicing events are increased by skip-1 in the absence and present of ABA. Our results first reveal a principle on how a splicing factor affects the ABA signaling.