@article{wheeler_brooks_concia_vera_wear_leblanc_ramu_vaughn_bass_martienssen_et al._2020, title={Arabidopsis DNA Replication Initiates in Intergenic, AT-Rich Open Chromatin(1)([OPEN])}, volume={183}, ISSN={["1532-2548"]}, DOI={10.1104/pp.19.01520}, abstractNote={DNA replication initiation sites in plants associate most strongly with AT-rich and highly accessible chromatin, and not with genes or a particular epigenetic signature. The selection and firing of DNA replication origins play key roles in ensuring that eukaryotes accurately replicate their genomes. This process is not well documented in plants due in large measure to difficulties in working with plant systems. We developed a new functional assay to label and map very early replicating loci that must, by definition, include at least a subset of replication origins. Arabidopsis (Arabidopsis thaliana) cells were briefly labeled with 5-ethynyl-2′-deoxy-uridine, and nuclei were subjected to two-parameter flow sorting. We identified more than 5500 loci as initiation regions (IRs), the first regions to replicate in very early S phase. These were classified as strong or weak IRs based on the strength of their replication signals. Strong initiation regions were evenly spaced along chromosomal arms and depleted in centromeres, while weak initiation regions were enriched in centromeric regions. IRs are AT-rich sequences flanked by more GC-rich regions and located predominantly in intergenic regions. Nuclease sensitivity assays indicated that IRs are associated with accessible chromatin. Based on these observations, initiation of plant DNA replication shows some similarity to, but is also distinct from, initiation in other well-studied eukaryotic systems.}, number={1}, journal={PLANT PHYSIOLOGY}, author={Wheeler, Emily and Brooks, Ashley M. and Concia, Lorenzo and Vera, Daniel L. and Wear, Emily E. and LeBlanc, Chantal and Ramu, Umamaheswari and Vaughn, Matthew W. and Bass, Hank W. and Martienssen, Robert A. and et al.}, year={2020}, month={May}, pages={206–220} }
 @article{wear_song_zynda_mickelson-young_leblanc_lee_deppong_allen_martienssen_vaughn_et al._2020, title={Comparing DNA replication programs reveals large timing shifts at centromeres of endocycling cells in maize roots}, volume={16}, ISSN={["1553-7404"]}, DOI={10.1371/journal.pgen.1008623}, abstractNote={Plant cells undergo two types of cell cycles–the mitotic cycle in which DNA replication is coupled to mitosis, and the endocycle in which DNA replication occurs in the absence of cell division. To investigate DNA replication programs in these two types of cell cycles, we pulse labeled intact root tips of maize (Zea mays) with 5-ethynyl-2’-deoxyuridine (EdU) and used flow sorting of nuclei to examine DNA replication timing (RT) during the transition from a mitotic cycle to an endocycle. Comparison of the sequence-based RT profiles showed that most regions of the maize genome replicate at the same time during S phase in mitotic and endocycling cells, despite the need to replicate twice as much DNA in the endocycle and the fact that endocycling is typically associated with cell differentiation. However, regions collectively corresponding to 2% of the genome displayed significant changes in timing between the two types of cell cycles. The majority of these regions are small with a median size of 135 kb, shift to a later RT in the endocycle, and are enriched for genes expressed in the root tip. We found larger regions that shifted RT in centromeres of seven of the ten maize chromosomes. These regions covered the majority of the previously defined functional centromere, which ranged between 1 and 2 Mb in size in the reference genome. They replicate mainly during mid S phase in mitotic cells but primarily in late S phase of the endocycle. In contrast, the immediately adjacent pericentromere sequences are primarily late replicating in both cell cycles. Analysis of CENH3 enrichment levels in 8C vs 2C nuclei suggested that there is only a partial replacement of CENH3 nucleosomes after endocycle replication is complete. The shift to later replication of centromeres and possible reduction in CENH3 enrichment after endocycle replication is consistent with a hypothesis that centromeres are inactivated when their function is no longer needed.}, number={10}, journal={PLOS GENETICS}, author={Wear, Emily E. and Song, Jawon and Zynda, Gregory J. and Mickelson-Young, Leigh and LeBlanc, Chantal and Lee, Tae-Jin and Deppong, David O. and Allen, George C. and Martienssen, Robert A. and Vaughn, Matthew W. and et al.}, year={2020}, month={Oct} }
 @article{borges_donoghue_leblanc_wear_tanurdzic_berube_brooks_thompson_hanley-bowdoin_martienssen_2021, title={Loss of Small-RNA-Directed DNA Methylation in the Plant Cell Cycle Promotes Germline Reprogramming and Somaclonal Variation}, volume={31}, ISBN={1879-0445}, url={https://doi.org/10.1016/j.cub.2020.10.098}, DOI={10.1016/j.cub.2020.10.098}, abstractNote={5-methyl cytosine is widespread in plant genomes in both CG and non-CG contexts. During replication, hemi-methylation on parental DNA strands guides symmetric CG methylation on nascent strands, but non-CG methylation requires modified histones and small RNA guides. Here, we used immortalized Arabidopsis cell suspensions to sort replicating nuclei and determine genome-wide cytosine methylation dynamics during the plant cell cycle. We find that symmetric mCG and mCHG are selectively retained in actively dividing cells in culture, whereas mCHH is depleted. mCG becomes transiently asymmetric during S phase but is rapidly restored in G2, whereas mCHG remains asymmetric throughout the cell cycle. Hundreds of loci gain ectopic CHG methylation, as well as 24-nt small interfering RNAs (siRNAs) and histone H3 lysine dimethylation (H3K9me2), without gaining CHH methylation. This suggests that spontaneous epialleles that arise in plant cell cultures are stably maintained by siRNA and H3K9me2 independent of the canonical RNA-directed DNA methylation (RdDM) pathway. In contrast, loci that fail to produce siRNA may be targeted for demethylation when the cell cycle arrests. Comparative analysis with methylomes of various tissues and cell types suggests that loss of small-RNA-directed non-CG methylation during DNA replication promotes germline reprogramming and epigenetic variation in plants propagated as clones.}, number={3}, journal={CURRENT BIOLOGY}, publisher={Elsevier BV}, author={Borges, Filipe and Donoghue, Mark T. A. and LeBlanc, Chantal and Wear, Emily E. and Tanurdzic, Milos and Berube, Benjamin and Brooks, Ashley and Thompson, William F. and Hanley-Bowdoin, Linda and Martienssen, Robert A.}, year={2021}, pages={591-+} }
 @article{turpin_vera_savadel_lung_wear_mickelson-young_thompson_hanley-bowdoin_dennis_zhang_et al._2018, title={Chromatin structure profile data from DNS-seq: Differential nuclease sensitivity mapping of four reference tissues of B73 maize (Zea mays L)}, volume={20}, ISSN={["2352-3409"]}, DOI={10.1016/j.dib.2018.08.015}, abstractNote={Presented here are data from Next-Generation Sequencing of differential micrococcal nuclease digestions of formaldehyde-crosslinked chromatin in selected tissues of maize (Zea mays) inbred line B73. Supplemental materials include a wet-bench protocol for making DNS-seq libraries, the DNS-seq data processing pipeline for producing genome browser tracks. This report also includes the peak-calling pipeline using the iSeg algorithm to segment positive and negative peaks from the DNS-seq difference profiles. The data repository for the sequence data is the NCBI SRA, BioProject Accession PRJNA445708.}, journal={DATA IN BRIEF}, author={Turpin, Zachary M. and Vera, Daniel L. and Savadel, Savannah D. and Lung, Pei-Yau and Wear, Emily E. and Mickelson-Young, Leigh and Thompson, William F. and Hanley-Bowdoin, Linda and Dennis, Jonathan H. and Zhang, Jinfeng and et al.}, year={2018}, month={Oct}, pages={358–363} }
 @article{concia_brooks_wheeler_zynda_wear_leblanc_song_lee_pascuzzi_martienssen_et al._2018, title={Genome-Wide Analysis of the Arabidopsis Replication Timing Program}, volume={176}, ISSN={["1532-2548"]}, url={http://europepmc.org/abstract/med/29301956}, DOI={10.1104/pp.17.01537}, abstractNote={The Arabidopsis genome replicates in two noninteracting compartments during early/mid and late S phase. Eukaryotes use a temporally regulated process, known as the replication timing program, to ensure that their genomes are fully and accurately duplicated during S phase. Replication timing programs are predictive of genomic features and activity and are considered to be functional readouts of chromatin organization. Although replication timing programs have been described for yeast and animal systems, much less is known about the temporal regulation of plant DNA replication or its relationship to genome sequence and chromatin structure. We used the thymidine analog, 5-ethynyl-2′-deoxyuridine, in combination with flow sorting and Repli-Seq to describe, at high-resolution, the genome-wide replication timing program for Arabidopsis (Arabidopsis thaliana) Col-0 suspension cells. We identified genomic regions that replicate predominantly during early, mid, and late S phase, and correlated these regions with genomic features and with data for chromatin state, accessibility, and long-distance interaction. Arabidopsis chromosome arms tend to replicate early while pericentromeric regions replicate late. Early and mid-replicating regions are gene-rich and predominantly euchromatic, while late regions are rich in transposable elements and primarily heterochromatic. However, the distribution of chromatin states across the different times is complex, with each replication time corresponding to a mixture of states. Early and mid-replicating sequences interact with each other and not with late sequences, but early regions are more accessible than mid regions. The replication timing program in Arabidopsis reflects a bipartite genomic organization with early/mid-replicating regions and late regions forming separate, noninteracting compartments. The temporal order of DNA replication within the early/mid compartment may be modulated largely by chromatin accessibility.}, number={3}, journal={PLANT PHYSIOLOGY}, author={Concia, Lorenzo and Brooks, Ashley M. and Wheeler, Emily and Zynda, Gregory J. and Wear, Emily E. and LeBlanc, Chantal and Song, Jawon and Lee, Tae-Jin and Pascuzzi, Pete E. and Martienssen, Robert A. and et al.}, year={2018}, month={Mar}, pages={2166–2185} }
 @article{wear_song_zynda_leblanc_lee_mickelson-young_concia_mulvaney_szymanski_allen_et al._2017, title={Genomic Analysis of the DNA Replication Timing Program during Mitotic S Phase in Maize (Zea mays) Root Tips}, volume={29}, ISSN={["1532-298X"]}, url={http://europepmc.org/abstract/med/28842533}, DOI={10.1105/tpc.17.00037}, abstractNote={The time during S phase at which different maize DNA sequences replicate reveals a complex temporal program influenced by genomic features, transcriptional activity, and chromatin structure. All plants and animals must replicate their DNA, using a regulated process to ensure that their genomes are completely and accurately replicated. DNA replication timing programs have been extensively studied in yeast and animal systems, but much less is known about the replication programs of plants. We report a novel adaptation of the “Repli-seq” assay for use in intact root tips of maize (Zea mays) that includes several different cell lineages and present whole-genome replication timing profiles from cells in early, mid, and late S phase of the mitotic cell cycle. Maize root tips have a complex replication timing program, including regions of distinct early, mid, and late S replication that each constitute between 20 and 24% of the genome, as well as other loci corresponding to ∼32% of the genome that exhibit replication activity in two different time windows. Analyses of genomic, transcriptional, and chromatin features of the euchromatic portion of the maize genome provide evidence for a gradient of early replicating, open chromatin that transitions gradually to less open and less transcriptionally active chromatin replicating in mid S phase. Our genomic level analysis also demonstrated that the centromere core replicates in mid S, before heavily compacted classical heterochromatin, including pericentromeres and knobs, which replicate during late S phase.}, number={9}, journal={PLANT CELL}, author={Wear, Emily E. and Song, Jawon and Zynda, Gregory J. and LeBlanc, Chantal and Lee, Tae-Jin and Mickelson-Young, Leigh and Concia, Lorenzo and Mulvaney, Patrick and Szymanski, Eric S. and Allen, George C. and et al.}, year={2017}, month={Sep}, pages={2126–2149} }
 @article{zynda_song_concia_wear_hanley-bowdoin_thompson_vaughn_2017, title={Repliscan: a tool for classifying replication timing regions}, volume={18}, ISSN={["1471-2105"]}, url={http://europepmc.org/abstract/med/28784090}, DOI={10.1186/s12859-017-1774-x}, abstractNote={Replication timing experiments that use label incorporation and high throughput sequencing produce peaked data similar to ChIP-Seq experiments. However, the differences in experimental design, coverage density, and possible results make traditional ChIP-Seq analysis methods inappropriate for use with replication timing.To accurately detect and classify regions of replication across the genome, we present Repliscan. Repliscan robustly normalizes, automatically removes outlying and uninformative data points, and classifies Repli-seq signals into discrete combinations of replication signatures. The quality control steps and self-fitting methods make Repliscan generally applicable and more robust than previous methods that classify regions based on thresholds.Repliscan is simple and effective to use on organisms with different genome sizes. Even with analysis window sizes as small as 1 kilobase, reliable profiles can be generated with as little as 2.4x coverage.}, journal={BMC BIOINFORMATICS}, author={Zynda, Gregory J. and Song, Jawon and Concia, Lorenzo and Wear, Emily E. and Hanley-Bowdoin, Linda and Thompson, William F. and Vaughn, Matthew W.}, year={2017}, month={Aug}, pages={1–14} }
 @article{mickelson-young_wear_mulvaney_lee_szymanski_allen_hanley-bowdoin_thompson_2016, title={A flow cytometric method for estimating S-phase duration in plants}, volume={67}, ISSN={["1460-2431"]}, url={http://europepmc.org/abstract/med/27697785}, DOI={10.1093/jxb/erw367}, abstractNote={Highlight We estimated S-phase duration for several plant species by following EdU-labeled nuclei from G1 to G2 using bivariate flow cytometry. S-phase duration is relatively consistent over a range of genome sizes.}, number={21}, journal={JOURNAL OF EXPERIMENTAL BOTANY}, author={Mickelson-Young, Leigh and Wear, Emily and Mulvaney, Patrick and Lee, Tae-Jin and Szymanski, Eric S. and Allen, George and Hanley-Bowdoin, Linda and Thompson, William}, year={2016}, month={Nov}, pages={6077–6087} }
 @article{bass_hoffman_lee_wear_joseph_allen_hanley-bowdoin_thompson_2015, title={Defining multiple, distinct, and shared spatiotemporal patterns of DNA replication and endoreduplication from 3D image analysis of developing maize (Zea mays L.) root tip nuclei}, volume={89}, ISSN={["1573-5028"]}, DOI={10.1007/s11103-015-0364-4}, abstractNote={Spatiotemporal patterns of DNA replication have been described for yeast and many types of cultured animal cells, frequently after cell cycle arrest to aid in synchronization. However, patterns of DNA replication in nuclei from plants or naturally developing organs remain largely uncharacterized. Here we report findings from 3D quantitative analysis of DNA replication and endoreduplication in nuclei from pulse-labeled developing maize root tips. In both early and middle S phase nuclei, flow-sorted on the basis of DNA content, replicative labeling was widely distributed across euchromatic regions of the nucleoplasm. We did not observe the perinuclear or perinucleolar replicative labeling patterns characteristic of middle S phase in mammals. Instead, the early versus middle S phase patterns in maize could be distinguished cytologically by correlating two quantitative, continuous variables, replicative labeling and DAPI staining. Early S nuclei exhibited widely distributed euchromatic labeling preferentially localized to regions with weak DAPI signals. Middle S nuclei also exhibited widely distributed euchromatic labeling, but the label was preferentially localized to regions with strong DAPI signals. Highly condensed heterochromatin, including knobs, replicated during late S phase as previously reported. Similar spatiotemporal replication patterns were observed for both mitotic and endocycling maize nuclei. These results revealed that maize euchromatin exists as an intermingled mixture of two components distinguished by their condensation state and replication timing. These different patterns might reflect a previously described genome organization pattern, with "gene islands" mostly replicating during early S phase followed by most of the intergenic repetitive regions replicating during middle S phase.}, number={4-5}, journal={PLANT MOLECULAR BIOLOGY}, author={Bass, Hank W. and Hoffman, Gregg G. and Lee, Tae-Jin and Wear, Emily E. and Joseph, Stacey R. and Allen, George C. and Hanley-Bowdoin, Linda and Thompson, William F.}, year={2015}, month={Nov}, pages={339–351} }
 @article{tipping_martin_nimmo_pierce_smart_white_madeira_center_2009, title={Invasion of a West Everglades wetland by Melaleuca quinquenervia countered by classical biological control}, volume={48}, ISSN={["1090-2112"]}, DOI={10.1016/j.biocontrol.2008.08.018}, abstractNote={The population dynamics of Melaleuca quinquenervia were monitored over a 5-year period in a cypress-pine wetland while subjected to two levels of herbivory. The trees had been recruited during 1998–1999 after a destructive crown fire. Half of 26 experimental plots were sprayed every 4–6 weeks with an insecticide to reduce herbivory by the biological control agents Oxyops vitiosa and Boreioglycaspis melaleucae. After only 1-year melaleuca density increased by 26% in sprayed plots and by 7% in unsprayed plots. However, over the entire 5-year period melaleuca density increased in sprayed plots by 0.1% while decreasing by 47.9% in unsprayed plots when compared to initial densities. Annual mortality of melaleuca never exceeded 6% in any year in sprayed plots but ranged from 11% to 25% in unsprayed plots. There was a significant year by treatment interaction indicating the importance of the environment on tree mortality. Limited seed production occurred on sprayed trees but never on unsprayed trees. Mean tree height increased by 19.6% in sprayed plots while declining by 30.6% in unsprayed plots. Coverage by native vegetation did not increase with decreasing melaleuca density. This is the first study with controls that quantifies the population level regulation of melaleuca by introduced biological control agents and corroborates other correlative studies that documented significant changes in melaleuca communities after the introduction and establishment of biological control agents.}, number={1}, journal={BIOLOGICAL CONTROL}, author={Tipping, Philip W. and Martin, Melissa R. and Nimmo, Kayla R. and Pierce, Ryan M. and Smart, Matthew D. and White, Emily and Madeira, Paul T. and Center, Ted D.}, year={2009}, month={Jan}, pages={73–78} }