Project description:The goal of the experiment was to perform a large scale study of circadian regulation of gene expression in maize. To identify maize genes with expression regulated by the circadian clock, transcript levels in the aerial tissues of young maize seedlings were determined by transcriptional profiling with the Affymetrix GeneChip Maize Genome Array. Maize inbred B73 seedlings were grown inside Conviron growth chamber. B73 seedlings were grown for 7 days under 12 h light:12 h dark (LD) photocycles, 26° C temperature and 70% humidity. At the 8th day, seedlings were transferred to continuous light (LL) and were allowed to entrain completely for 24 h prior to tissue harvest following which tissue was harvested every 4 hours under LL conditions for a period of 48h. Therefore, for the circadian LL time course 12 time points were collected as follows (also defined as factors in the treatment section): ZT0 - 8:00 am/ subjective dawn/ Day1 ZT4 - 12:00 pm/ subjective mid-day/ Day1 ZT8 - 4:00 pm/ subjective late-day/ Day1 ZT12 - 8:00 pm/ subjective dusk/ Day1 ZT16 - 12:00 am/ subjective mid-night/ Day1 ZT20 - 4:00 am/ subjective pre-dawn/ Day1 ZT24- 8:00 am/ subjective dawn/ Day2 ZT28 - 12:00 pm/ subjective mid-day/ Day2 ZT32 - 4:00 pm/ subjective late-day/ Day2 ZT36 - 8:00 pm/ subjective dusk/ Day2 ZT40 - 12:00 am/ subjective mid-night/ Day2 ZT44 - 4:00 am/ subjective pre-dawn/ Day2 Tissue comprised of aerial portion of the seedlings (corresponding to tissue from the prop roots and up) for RNA isolation. Total RNA was isolated from the entire aerial portion of 7 day-old seedlings (corresponding to tissue from the prop roots and up) by Trizol extraction followed by Qiagen RNeasy columns and treatment with RNase-free DNase I (Qiagen; qiagen.com). RNA was isolated from 3 independent biological replicates was pooled. cRNA was generated from pooled total RNA from 3 biological replicates with the GeneChip One-Cycle Target Labeling kit according to the manufacturer’s recommendations (Affymetrix, affymetrix.com). The University of California, Berkeley Functional Genomics Laboratory hybridized samples to Affymetrix GeneChip Maize Genome Arrays and scanned the washed arrays as suggested by manufacturer. Probe sets called “Not Present” or “Marginal” on one or more microarrays were removed from the downstream analysis, as is common practice with circadian studies. Raw hybridization intensities were normalized across all twelve arrays using RMA express in Perfect Match mode. ****[PLEXdb(http://www.plexdb.org) has submitted this series at GEO on behalf of the original contributor, Frank G. Harmon. The equivalent experiment is ZM28 at PLEXdb.] Continuous Light: ZT0(1-replications); Continuous Light: ZT4(1-replications); Continuous Light: ZT8(1-replications); Continuous Light: ZT12(1-replications); Continuous Light: ZT16(1-replications); Continuous Light: ZT20(1-replications); Continuous Light: ZT24(1-replications); Continuous Light: ZT28(1-replications); Continuous Light: ZT32(1-replications); Continuous Light: ZT36(1-replications); Continuous Light: ZT40(1-replications); Continuous Light: ZT44(1-replications)

Project description:The goal of the experiment was to perform a large scale study of circadian regulation of gene expression in maize. To identify maize genes with expression regulated by the circadian clock, transcript levels in the aerial tissues of young maize seedlings were determined by transcriptional profiling with the Affymetrix GeneChip Maize Genome Array. Maize inbred B73 seedlings were grown inside Conviron growth chamber. B73 seedlings were grown for 7 days under 12 h light:12 h dark (LD) photocycles, 26° C temperature and 70% humidity. At the 8th day, seedlings were transferred to continuous light (LL) and were allowed to entrain completely for 24 h prior to tissue harvest following which tissue was harvested every 4 hours under LL conditions for a period of 48h. Therefore, for the circadian LL time course 12 time points were collected as follows (also defined as factors in the treatment section): ZT0 - 8:00 am/ subjective dawn/ Day1 ZT4 - 12:00 pm/ subjective mid-day/ Day1 ZT8 - 4:00 pm/ subjective late-day/ Day1 ZT12 - 8:00 pm/ subjective dusk/ Day1 ZT16 - 12:00 am/ subjective mid-night/ Day1 ZT20 - 4:00 am/ subjective pre-dawn/ Day1 ZT24- 8:00 am/ subjective dawn/ Day2 ZT28 - 12:00 pm/ subjective mid-day/ Day2 ZT32 - 4:00 pm/ subjective late-day/ Day2 ZT36 - 8:00 pm/ subjective dusk/ Day2 ZT40 - 12:00 am/ subjective mid-night/ Day2 ZT44 - 4:00 am/ subjective pre-dawn/ Day2 Tissue comprised of aerial portion of the seedlings (corresponding to tissue from the prop roots and up) for RNA isolation. Total RNA was isolated from the entire aerial portion of 7 day-old seedlings (corresponding to tissue from the prop roots and up) by Trizol extraction followed by Qiagen RNeasy columns and treatment with RNase-free DNase I (Qiagen; qiagen.com). RNA was isolated from 3 independent biological replicates was pooled. cRNA was generated from pooled total RNA from 3 biological replicates with the GeneChip One-Cycle Target Labeling kit according to the manufacturer’s recommendations (Affymetrix, affymetrix.com). The University of California, Berkeley Functional Genomics Laboratory hybridized samples to Affymetrix GeneChip Maize Genome Arrays and scanned the washed arrays as suggested by manufacturer. Probe sets called “Not Present” or “Marginal” on one or more microarrays were removed from the downstream analysis, as is common practice with circadian studies. Raw hybridization intensities were normalized across all twelve arrays using RMA express in Perfect Match mode. ****[PLEXdb(http://www.plexdb.org) has submitted this series at GEO on behalf of the original contributor, Frank G. Harmon. The equivalent experiment is ZM28 at PLEXdb.]

Project description:Chilling stress is a major abiotic stress that affects rice growth and development. Rice seedlings are quite sensitive to chilling stress and this harms global rice production. Comprehensive studies of the molecular mechanisms for response to low temperature are of fundamental importance to chilling tolerance improvement. The number of identified cold regulated genes (CORs) in rice is still very small. Circadian clock is an endogenous timer that enables plants to cope with forever changing surroundings including light–dark cycles imposed by the rotation of the planet. Previous studies have demonstrated that the circadian clock regulates stress tolerances in plants show circadian clock regulation of plant stress tolerances. However, little is known about coordination of the circadian clock in rice chilling tolerance. In this study, we investigated rice responses to chilling stress under conditions with natural light-dark cycles. We demonstrated that chilling stress occurring at nighttime significantly decreased chlorophyll content and photosynthesis efficiency in comparison with that occurring at daytime. Transcriptome analysis characterized novel CORs in indica rice, and suggested that circadian clock obviously interferes with cold effects on key genes in chlorophyll (Chl) biosynthesis pathway and photosynthesis-antenna proteins. Expression profiling revealed that chilling stress during different Zeitberger times (ZTs) at nighttime repressed the expression of those genes involved Chl biosynthesis and photosynthesis, whereas stress during ZTs at daytime increases their expression dramatically. Moreover, marker genes OsDREBs for chilling tolerance were regulated differentially by the chilling stress occurring at different ZTs. The phase and amplitude of oscillation curves of core clock component genes such as OsLHY and OsPRR1 are regulated by chilling stress, suggesting the role of chilling stress as an input signal to the rice circadian clock. Our work revealed impacts of circadian clock on chilling responses in rice, and proved that the effects on the fitness costs are varying with the time in a day when the chilling stress occurs.

Dataset Information

Coordination of the maize transcriptome by a conserved circadian clock.

Publications

Coordination of the maize transcriptome by a conserved circadian clock.

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