Summary: Cytosine DNA methylation (mC) is a genome modification that can regulate the expression of coding and non-coding genetic elements. However, little is known about the involvement of mC in response to environmental cues. Using whole genome bisulfite sequencing to assess the spatio-temporal dynamics of mC in rice grown under phosphate starvation and recovery conditions, we identified widespread phosphate starvation-induced changes in mC, preferentially localized in transposable elements (TEs) close to highly induced genes. These changes in mC occurred after changes in nearby gene transcription, were mostly DCL3a-independent, and could partially be propagated through mitosis, however no evidence of meiotic transmission was observed. Similar analyses performed in Arabidopsis revealed a very limited effect of phosphate starvation on mC, suggesting a species-specific mechanism. Overall, this suggests that TEs in proximity to environmentally induced genes are silenced via hypermethylation, and establishes the temporal hierarchy of transcriptional and epigenomic changes in response to stress.
Overall Design: RNA-Seq of rice DCL3a and Wild type root (+Pi/-Pi), respectively.
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Growth Protocol: | Rice (Oryza sativa L. cv. Nipponbare) was used for all physiological experiments. Hydroponic experiments were performed under controlled conditions (day/night temperature of 30/22°C and a 12 hr photoperiod, 200 µmol photons m-2 s-1), allowing 0.5 l of hydroponic solution per plant. The hydroponic solution consisted of a modified solution as described in (Secco et al., 2013a), containing 1.425 mM NH4NO3, 0.513 mM K2SO4, 0.998 mM CaCl2, 1.643 mM MgSO4, 0.075 µM (NH4)6Mo7O24, 0.25 mM NaSiO3, 0.009 mM MnCl2, 0.019 µM H3BO3, 0.155 µM CuSO4, 0.152 µM ZnSO4 and 0.125 mM EDTA-Fe, with or without 0.323 mM NaH2PO4, resulting in the +Pi and -Pi conditions. The pH of the solution was adjusted to 5.5 and the solution was renewed every 3 day. |
Treatment Protocol: | Rice seeds were first pre-germinated in tap water for 2 days before being transferred into the hydroponic solution, containing 0.323 mM Pi (+Pi) for 2 weeks. Half of the seedlings were then transferred to a solution lacking Pi (0 mM Pi) for 21 days, before being re-supplemented with 0.323 mM Pi for up to 31 days, while the other half of the seedlings continuously remained in +Pi conditions (control). During the resupply experiment, half of the rice seedlings were left in Pi deficient media, to serve as control. After 24 days of Pi starvation, plants grown under Pi deficient conditions were supplemented with 0.03 mM Pi (1/10th of Pi sufficient Pi concentration) until the end of the experiment to prevent them from dying. |
Extract Protocol: | The total RNA from the roots tissues was extracted using TRIzol reagent (Invitrogen, Carlsbad, CA), according to the manufacturer's instructions. |
Library Construction Protocol: | For RNA-seq library synthesis, total RNA was first depleted of rRNA using the Ribo-Zero rRNA removal kit (Plant Leaf, and Plant Seed/Root kits, Epicentre, Madison, WI). To do so, 1 µg of total RNA from root samples was used as input for rRNA removal. Sequencing libraries were generated using the TruSeq RNA Sample Prep Kit (Illumina, San Diego, CA). |
Molecule Type: | rRNA- RNA |
Library Source: | |
Library Layout: | SINGLE |
Library Strand: | Forward |
Platform: | ILLUMINA |
Instrument Model: | Illumina HiSeq 1000 |
Strand-Specific: | Specific |
Data Resource | GEN Sample ID | GEN Dataset ID | Project ID | BioProject ID | Sample ID | Sample Name | BioSample ID | Sample Accession | Experiment Accession | Release Date | Submission Date | Update Date | Species | Race | Ethnicity | Age | Age Unit | Gender | Source Name | Tissue | Cell Type | Cell Subtype | Cell Line | Disease | Disease State | Development Stage | Mutation | Phenotype | Case Detail | Control Detail | Growth Protocol | Treatment Protocol | Extract Protocol | Library Construction Protocol | Molecule Type | Library Layout | Strand-Specific | Library Strand | Spike-In | Strategy | Platform | Instrument Model | Cell Number | Reads Number | Gbases | AvgSpotLen1 | AvgSpotLen2 | Uniq Mapping Rate | Multiple Mapping Rate | Coverage Rate |
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