Diurnal cycle effect on whole leaf, mesophyll and vasculature: time course
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ABSTRACT: Many organisms acquired circadian clock system to adapt daily and seasonal environmental changes. Mammals have the master clock in the brains’ suprachiasmatic nucleus (SCN) that synchronizes other circadian clocks in the peripheral tissues or organs. Plants also have circadian clock in their bodies, but the presence of the tissue-specific functions of circadian clock is remained elusive. The aim of this experiment is to compare tissue-specific gene expression profile using gene expression Microarray. The study was designed to compare the tissue-specific regulation of gene expression between tissues and between day lengths. All experiments were performed in 9-day-old wild type (Col-0) grown under long day and short day conditions. Whole leaf, mesophyll and vasculature were isolated every four hours over two days. The total numbers of used arrays were 72 Affymetrix Arabidopsis Gene 1.0 ST arrays. We detected cyclling genes with an FDR<3% using HAYSTACK (http://haystack.mocklerlab.org).
Project description:Many organisms acquired circadian clock system to adapt daily and seasonal environmental changes. Mammals have the master clock in the brains’ suprachiasmatic nucleus (SCN) that synchronizes other circadian clocks in the peripheral tissues or organs. Plants also have circadian clock in their bodies, but the presence of the tissue-specific functions of circadian clock is remained elusive. The aim of this experiment is to compare tissue-specific gene expression profile using gene expression Microarray.
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). 10 day-old wild type and CCA1-ox (described in Cell. 1998 Jun 26;93(7):1207-17) Arabidopsis seedlings were harvested at 6am (Zeitgeber time ZT0), 12pm (ZT6), 6pm (ZT12), and 12am (ZT18), with 3 replicates for each time and genotype.
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). 10 day-old wild type and CCA1-ox (described in Cell. 1998 Jun 26;93(7):1207-17) Arabidopsis seedlings were harvested at 6am (Zeitgeber time ZT0), 12pm (ZT6), 6pm (ZT12), and 12am (ZT18), with 3 replicates for each time and genotype.
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). 10 day-old wild type and CCA1-ox (described in Cell. 1998 Jun 26;93(7):1207-17) Arabidopsis seedlings were harvested at 6am (Zeitgeber time ZT0), 12pm (ZT6), 6pm (ZT12), and 12am (ZT18), with 3 replicates for each time and genotype.
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). 10 day-old wild type and CCA1-ox (described in Cell. 1998 Jun 26;93(7):1207-17) Arabidopsis seedlings were harvested at 6am (Zeitgeber time ZT0), 12pm (ZT6), 6pm (ZT12), and 12am (ZT18), with 3 replicates for each time and genotype.
Project description:The circadian clock represents an evolutionarily acquired gene network that synchronizes physiology to anticipate environmental changes caused by the succession of day and night. While most mammalian cells have a circadian clock, their synchronization depends on a central pacemaker located in the suprachiasmatic nuclei (SCN) of the hypothalamus that integrates light signals. While peripheral organs can be also synchronized by feeding cues and can be uncoupled from the central pacemaker, no impact of peripheral organs on the central clock has been yet observed. Here, we used a mouse chimeric model in which mouse hepatocytes have been replaced by human hepatocytes that have different circadian and signaling properties to characterize such potential feedback. Remarkably, we observed that liver humanization rewired the liver diurnal gene expression and advance the circadian clock by approximately 4 hours. Strikingly, this phase advance was also observed in the muscle and for the entire rhythmic physiology of the animals, with an impact of human hepatocytes on the circadian function of the central clock. Like mice with a deficient central clock, the humanized animals shifted their physiology more rapidly to the light phase under day feeding. This data prompt to reconsider the role of peripheral clocks on the central pacemaker and offers new perspective to understand the impact of diseased organs on the global circadian physiology.
Project description:The mammalian circadian timing system consists of a master pacemaker in the suprachiasmatic nucleus (SCN) that synchronizes self-sustained oscillators in most peripheral cells. Rhythmic gene expression in peripheral tissues can be driven by cyclic systemic cues emanating from the SCN or by local oscillators. To discriminate between these two mechanisms, we engineered a mouse strain with a conditionally active liver clock. Transcriptome profiling revealed that the circadian transcription of most genes depends on functional hepatocyte clocks. However, the expression of 31 genes, including mPer2, oscillates robustly in clock-arrested hepatocytes. Such genes may be implicated in the synchronization of liver oscillators
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:In most organisms biological processes are partitioned, or phased to specific times over the day through interactions between external cycles of temperature (thermocycles) and light (photocycles), and the endogenous circadian clock. This orchestration of biological activities is achieved in part through an underlying transcriptional network. To understand how thermocycles, photocycles and the circadian clock interact to control time of day specific transcript abundance in Arabidopsis thaliana, we conducted four diurnal and three circadian two-day time courses using Affymetrix GeneChips (ATH1). All time courses were carried out with seven-day-old seedlings grown on agar plates under thermocycles (HC, hot/cold) and/or photocycles (LD, light/dark), or continuous conditions (LL, continuous light; DD, continuous dark, HH, continuous hot). Whole seedlings (50-100), including roots, stems and leaves were collected every four hours and frozen in liquid nitrogen. The four time courses interrogating the interaction between thermocycles, photocycles and the circadian clock were carried out as two four-day time courses. Four-day time courses were divided into two days under diurnal conditions, and two days under circadian conditions of continuous light and temperature. Thermocycles of 12 hours at 22C (hot) and 12 hours at 12C (cold) were used in this study. The two time courses interrogating photoperiod were conducted under short days (8 hrs light and 16 hrs dark) or long days (16 hrs light and 8 hrs dark) under constant temperature. In addition, the photoperiod time courses were in the Landsberg erecta (ler) accession, in contrast to the other time courses that are in the Columbia (col) background. The final time course interrogated circadian rhythmicity in seedlings grown completely in the dark (etiolated). Dark grown seedlings were synchronized with thermocycles, and plants were sampled under the circadian conditions of continuous dark and temperature.
Project description:Light is a strong environmental cue that resets the circadian clock rhythm. We have used Affymetrix microarrays to profile the Drosophila head transcriptome response following a brief light pulse during the early night. Comparison of control (un-pulsed) and experimental flies reveal large number of differentially expressed transcripts underlying the process of light entrainment of the clock. Wild type flies exposed to light pulse at ZT15 compared to control group (no pulse)