Project description:Plants are sessile organisms that have acquired highly plastic developmental strategies to adapt to the environment. Among these processes, the floral transition is essential to ensure reproductive success and is finely regulated by several internal and external genetic networks. The photoperiodic pathway, which controls the plant response to day length, is one of the most important pathways controlling flowering. In Arabidopsis photoperiodic flowering, CONSTANS (CO) is the central gene activating the expression of the florigen FLOWERING LOCUS T (FT) in the leaves at the end of a long day. CO expression is strongly regulated by the circadian clock. However, to date, no evidence has been reported regarding a feedback loop from the photoperiod pathway back to the circadian clock. Using transcriptional networks, we have identified relevant network motifs regulating the interplay between the circadian clock and the photoperiod pathway. Gene expression, chromatin immunoprecipitation experiments and phenotypic analysis allowed us to elucidate the role of CO over the circadian clock. Plants with altered CO expression showed a different internal clock period, measured by daily rhythmic movements in the leaves. We show that CO is able to activate key genes related to the circadian clock, such as CCA1, LHY, PRR5 and GI, at the end of a long day by binding to specific sites on their promoters. Moreover, a significant number of PRR5 repressed target genes are upregulated by CO, and this could explain the phase transition promoted by CO. The CO-PRR5 complex interacts with the bZIP transcription factor HY5 and helps to localize the complex in the promoters of clock genes. Our results indicate that there may be a feedback loop in which CO communicates back to the circadian clock, feeding seasonal information to the circadian system.
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:Most higher organisms, including plants and animals, have developed a time-keeping mechanism that allows them to anticipate daily fluctuations of environmental parameters such as light and temperature. This circadian clock efficiently coordinates plant growth and metabolism with respect to time-of-day by producing self-sustained rhythms of gene expression with an approximately 24-hour period. The importance of these rhythms has in fact been demonstrated in both phytoplankton and higher plants: organisms that have an internal clock period matched to the external environment possess a competitive advantage over those that do not. We used microarrays to identify circadian-regulated genes of Arabidopsis thaliana to elucidate how the clock provides an adaptive advantage by understanding how the clock regulates outputs and determining which pathways and processes may be under circadian control. Keywords: time course
Project description:The circadian clock is comprised of proteins that form negative feedback loops, which regulate the timing of global gene expression in a coordinated 24 hour cycle. As a result, the plant circadian clock is responsible for regulating numerous physiological processes central to growth and survival. To date, most plant circadian clock studies have relied on diurnal transcriptome changes to elucidate molecular connections between the circadian clock and observable phenotypes in wild-type plants. Here, we have combined high-throughput RNA-sequencing and mass spectrometry to comparatively characterize the lhycca1, prr7prr9, gi and toc1 circadian clock mutant rosette transcriptome and proteome at the end-of-day and end-of-night.
Project description:Plants are sessile organisms that have acquired highly plastic developmental strategies to adapt to the environment. Among these processes, the floral transition is essential to ensure reproductive success and is finely regulated by several internal and external genetic networks. The photoperiodic pathway, which controls the plant response to day length, is one of the most important pathways controlling flowering. In Arabidopsis photoperiodic flowering, CONSTANS (CO) is the central gene activating the expression of the florigen FLOWERING LOCUS T (FT) in the leaves at the end of a long day. CO expression is strongly regulated by the circadian clock. However, to date, no evidence has been reported regarding a feedback loop from the photoperiod pathway back to the circadian clock. Using transcriptional networks, we have identified relevant network motifs regulating the interplay between the circadian clock and the photoperiod pathway. Gene expression, chromatin immunoprecipitation experiments and phenotypic analysis allowed us to elucidate the role of CO over the circadian clock. Plants with altered CO expression showed a different internal clock period, measured by daily rhythmic movements in the leaves. We show that CO is able to activate key genes related to the circadian clock, such as CCA1, LHY, PRR5 and GI, at the end of a long day by binding to specific sites on their promoters. Moreover, a significant number of PRR5 repressed target genes are upregulated by CO, and this could explain the phase transition promoted by CO. The CO-PRR5 complex interacts with the bZIP transcription factor HY5 and helps to localize the complex in the promoters of clock genes. Our results indicate that there may be a feedback loop in which CO communicates back to the circadian clock, feeding seasonal information to the circadian system.
Project description:Circadian control of gene expression has been established in plants at the transcriptional level, but relatively little is known about circadian control of translation. We used polysome profiling to characterize regulation of transcription and translation over a 24-hour diurnal cycle in Arabidopsis, both in wild type and in plants with a disrupted clock due to constitutive overexpression of the CIRCADIAN CLOCK ASSOCIATED 1 gene (CCA1-ox, AGI AT2G46830).
Project description:Circadian control of gene expression has been established in plants at the transcriptional level, but relatively little is known about circadian control of translation. We used polysome profiling to characterize regulation of transcription and translation over a 24-hour diurnal cycle in Arabidopsis, both in wild type and in plants with a disrupted clock due to constitutive overexpression of the CIRCADIAN CLOCK ASSOCIATED 1 gene (CCA1-ox, AGI AT2G46830).
Project description:Circadian control of gene expression has been established in plants at the transcriptional level, but relatively little is known about circadian control of translation. We used polysome profiling to characterize regulation of transcription and translation over a 24-hour diurnal cycle in Arabidopsis, both in wild type and in plants with a disrupted clock due to constitutive overexpression of the CIRCADIAN CLOCK ASSOCIATED 1 gene (CCA1-ox, AGI AT2G46830).