scholarly journals Natural depletion of H1 in sex cells causes DNA demethylation, heterochromatin decondensation and transposon activation

2018 ◽  
Author(s):  
Shengbo He ◽  
Martin Vickers ◽  
Jingyi Zhang ◽  
Xiaoqi Feng
Keyword(s):  
Arabidopsis Thaliana ◽  
Vegetative Cell ◽  
Progenitor Cell ◽  
Plant Cells ◽  
Dna Demethylation ◽  
Flowering Plant ◽  
Companion Cell ◽  
Male Gametogenesis ◽  
Independent Mechanism ◽  
Sex Cells

AbstractTransposable elements (TEs), the movement of which can damage the genome, are epigenetically silenced in eukaryotes. Intriguingly, TEs are activated in the sperm companion cell – vegetative cell (VC) – of the flowering plant Arabidopsis thaliana. However, the extent and mechanism of this activation are unknown. Here we show that about 100 heterochromatic TEs are activated in VCs, mostly by DEMETER-catalyzed DNA demethylation. We further demonstrate that DEMETER access to some of these TEs is permitted by the natural depletion of linker histone H1 in VCs. Ectopically expressed H1 suppresses TEs in VCs by reducing DNA demethylation and via a methylation-independent mechanism. We demonstrate that H1 is required for heterochromatin condensation in plant cells and show that H1 overexpression creates heterochromatic foci in the VC progenitor cell. Taken together, our results demonstrate that the natural depletion of H1 during male gametogenesis facilitates DEMETER-directed DNA demethylation, heterochromatin relaxation, and TE activation.

scholarly journals Natural depletion of histone H1 in sex cells causes DNA demethylation, heterochromatin decondensation and transposon activation

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Shengbo He ◽  
Martin Vickers ◽  
Jingyi Zhang ◽  
Xiaoqi Feng
Keyword(s):  
Progenitor Cell ◽  
Plant Cells ◽  
Histone H1 ◽  
Dna Demethylation ◽  
Flowering Plant ◽  
Companion Cell ◽  
Male Gametogenesis ◽  
Independent Mechanism ◽  
Sex Cells ◽  
Plant Arabidopsis Thaliana

Transposable elements (TEs), the movement of which can damage the genome, are epigenetically silenced in eukaryotes. Intriguingly, TEs are activated in the sperm companion cell – vegetative cell (VC) – of the flowering plant Arabidopsis thaliana. However, the extent and mechanism of this activation are unknown. Here we show that about 100 heterochromatic TEs are activated in VCs, mostly by DEMETER-catalyzed DNA demethylation. We further demonstrate that DEMETER access to some of these TEs is permitted by the natural depletion of linker histone H1 in VCs. Ectopically expressed H1 suppresses TEs in VCs by reducing DNA demethylation and via a methylation-independent mechanism. We demonstrate that H1 is required for heterochromatin condensation in plant cells and show that H1 overexpression creates heterochromatic foci in the VC progenitor cell. Taken together, our results demonstrate that the natural depletion of H1 during male gametogenesis facilitates DEMETER-directed DNA demethylation, heterochromatin relaxation, and TE activation.

scholarly journals Three-Dimensional Superresolution Imaging of the FtsZ Ring during Cell Division of the Cyanobacterium Prochlorococcus

mBio ◽  
2017 ◽  
Vol 8 (6) ◽  
Author(s):  
Riyue Liu ◽  
Yaxin Liu ◽  
Shichang Liu ◽  
Ying Wang ◽  
Kim Li ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Cell Division ◽  
Three Dimensional ◽  
Plant Cells ◽  
Flowering Plant ◽  
Superresolution Microscopy ◽  
Superresolution Imaging ◽  
Ftsz Ring ◽  
Cell Division Protein ◽  
Photosynthetic Cells

ABSTRACT Superresolution imaging has revealed subcellular structures and protein interactions in many organisms. However, superresolution microscopy with lateral resolution better than 100 nm has not been achieved in photosynthetic cells due to the interference of a high-autofluorescence background. Here, we developed a photobleaching method to effectively reduce the autofluorescence of cyanobacterial and plant cells. We achieved lateral resolution of ~10 nm with stochastic optical reconstruction microscopy (STORM) in the sphere-shaped cyanobacterium Prochlorococcus and the flowering plant Arabidopsis thaliana. During the cell cycle of Prochlorococcus, we characterized the three-dimensional (3D) organization of the cell division protein FtsZ, which forms a ring structure at the division site and is important for cytokinesis of bacteria and chloroplasts. Although the FtsZ ring assembly process in rod-shaped bacteria has been studied extensively, it has rarely been studied in sphere-shaped bacteria. Similarly to rod-shaped bacteria, our results with Prochlorococcus also showed the assembly of FtsZ clusters into incomplete rings and then complete rings during cell division. Differently from rod-shaped bacteria, the FtsZ ring diameter was not found to decrease during Prochlorococcus cell division. We also discovered a novel double-Z-ring structure, which may be the Z rings of two daughter cells in a predivisional mother cell. Our results showed a quantitative picture of the in vivo Z ring organization of sphere-shaped bacteria. IMPORTANCE Superresolution microscopy has not been widely used to study photosynthetic cells due to their high-autofluorescence background. Here, we developed a photobleaching method to reduce the autofluorescence of cyanobacteria and plant cells. After photobleaching, we performed superresolution imaging in the cyanobacterium Prochlorococcus and the flowering plant Arabidopsis thaliana with ~10-nm resolution, which is the highest resolution in a photosynthetic cell. With this method, we characterized the 3D organization of the cell division protein FtsZ in Prochlorococcus. We found that the morphological variation of the FtsZ ring during cell division of the sphere-shaped cyanobacterium Prochlorococcus is similar but not identical to that of rod-shaped bacteria. Our method might also be applicable to other photosynthetic organisms. IMPORTANCE Superresolution microscopy has not been widely used to study photosynthetic cells due to their high-autofluorescence background. Here, we developed a photobleaching method to reduce the autofluorescence of cyanobacteria and plant cells. After photobleaching, we performed superresolution imaging in the cyanobacterium Prochlorococcus and the flowering plant Arabidopsis thaliana with ~10-nm resolution, which is the highest resolution in a photosynthetic cell. With this method, we characterized the 3D organization of the cell division protein FtsZ in Prochlorococcus. We found that the morphological variation of the FtsZ ring during cell division of the sphere-shaped cyanobacterium Prochlorococcus is similar but not identical to that of rod-shaped bacteria. Our method might also be applicable to other photosynthetic organisms.

SAP130 and CSN1 interact and regulate male gametogenesis in Arabidopsis thaliana

2021 ◽  
Author(s):  
Shiori S. Aki ◽  
Kei Yura ◽  
Takashi Aoyama ◽  
Tomohiko Tsuge
Keyword(s):  
Arabidopsis Thaliana ◽  
Male Gametogenesis

An Analysis of Microsatellite Loci in Arabidopsis thaliana: Mutational Dynamics and Application

Genetics ◽  
2003 ◽  
Vol 165 (3) ◽  
pp. 1475-1488
Author(s):  
V Vaughan Symonds ◽  
Alan M Lloyd
Keyword(s):  
Arabidopsis Thaliana ◽  
Microsatellite Loci ◽  
Current Knowledge ◽  
Flowering Plant ◽  
Allele Frequency Distribution ◽  
Strongly Correlated ◽  
Microsatellite Evolution ◽  
Stepwise Mutation ◽  
Mutation Pattern ◽  
Infinite Alleles Model

Abstract Microsatellite loci are among the most commonly used molecular markers. These loci typically exhibit variation for allele frequency distribution within a species. However, the factors contributing to this variation are not well understood. To expand on the current knowledge of microsatellite evolution, 20 microsatellite loci were examined for 126 accessions of the flowering plant, Arabidopsis thaliana. Substantial variability in mutation pattern among loci was found, most of which cannot be explained by the assumptions of the traditional stepwise mutation model or infinite alleles model. Here it is shown that the degree of locus diversity is strongly correlated with the number of contiguous repeats, more so than with the total number of repeats. These findings support a strong role for repeat disruptions in stabilizing microsatellite loci by reducing the substrate for polymerase slippage and recombination. Results of cluster analyses are also presented, demonstrating the potential of microsatellite loci for resolving relationships among accessions of A. thaliana.

scholarly journals DNA demethylation by ROS1a in rice vegetative cells promotes methylation in sperm

2019 ◽  
Vol 116 (19) ◽  
pp. 9652-9657 ◽  
Author(s):  
M. Yvonne Kim ◽  
Akemi Ono ◽  
Stefan Scholten ◽  
Tetsu Kinoshita ◽  
Daniel Zilberman ◽  
...  
Keyword(s):  
Dna Methylation ◽  
Vegetative Cell ◽  
Seed Viability ◽  
Dna Demethylation ◽  
Central Cell ◽  
Dna Glycosylase ◽  
Rice Seed ◽  
Vegetative Cells ◽  
Active Dna Demethylation ◽  
Cell Genome

Epigenetic reprogramming is required for proper regulation of gene expression in eukaryotic organisms. In Arabidopsis, active DNA demethylation is crucial for seed viability, pollen function, and successful reproduction. The DEMETER (DME) DNA glycosylase initiates localized DNA demethylation in vegetative and central cells, so-called companion cells that are adjacent to sperm and egg gametes, respectively. In rice, the central cell genome displays local DNA hypomethylation, suggesting that active DNA demethylation also occurs in rice; however, the enzyme responsible for this process is unknown. One candidate is the rice REPRESSOR OF SILENCING1a (ROS1a) gene, which is related to DME and is essential for rice seed viability and pollen function. Here, we report genome-wide analyses of DNA methylation in wild-type and ros1a mutant sperm and vegetative cells. We find that the rice vegetative cell genome is locally hypomethylated compared with sperm by a process that requires ROS1a activity. We show that many ROS1a target sequences in the vegetative cell are hypomethylated in the rice central cell, suggesting that ROS1a also demethylates the central cell genome. Similar to Arabidopsis, we show that sperm non-CG methylation is indirectly promoted by DNA demethylation in the vegetative cell. These results reveal that DNA glycosylase-mediated DNA demethylation processes are conserved in Arabidopsis and rice, plant species that diverged 150 million years ago. Finally, although global non-CG methylation levels of sperm and egg differ, the maternal and paternal embryo genomes show similar non-CG methylation levels, suggesting that rice gamete genomes undergo dynamic DNA methylation reprogramming after cell fusion.

scholarly journals Distinct Peculiarities of In Planta Synthesis of Isoprenoid and Aromatic Cytokinins

Biomolecules ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 86
Author(s):  
Vladimir Oslovsky ◽  
Ekaterina Savelieva ◽  
Mikhail Drenichev ◽  
Georgy Romanov ◽  
Sergey Mikhailov
Keyword(s):  
Arabidopsis Thaliana ◽  
Plant Cells ◽  
Cytokinin Activity ◽  
Hormonal Activity ◽  
In Planta ◽  
Significant Difference ◽  
Aromatic Cytokinins ◽  
Derivatives Of ◽  
Ribose Moiety

The biosynthesis of aromatic cytokinins in planta, unlike isoprenoid cytokinins, is still unknown. To compare the final steps of biosynthesis pathways of aromatic and isoprenoid cytokinins, we synthesized a series of nucleoside derivatives of natural cytokinins starting from acyl-protected ribofuranosyl-, 2′-deoxyribofuranosyl- and 5′-deoxyribofuranosyladenine derivatives using stereoselective alkylation with further deblocking. Their cytokinin activity was determined in two bioassays based on model plants Arabidopsis thaliana and Amaranthus caudatus. Unlike active cytokinins-bases, cytokinin nucleosides lack the hormonal activity until the ribose moiety is removed. According to our experiments, ribo-, 2′-deoxyribo- and 5′-deoxyribo-derivatives of isoprenoid cytokinin N6-isopentenyladenine turned in planta into active cytokinins with clear hormonal activity. As for aromatic cytokinins, both 2′-deoxyribo- and 5′-deoxyribo-derivatives did not exhibit analogous activity in Arabidopsis. The 5′-deoxyribo-derivatives cannot be phosphorylated enzymatically in vivo; therefore, they cannot be “activated” by the direct LOG-mediated cleavage, largely occurring with cytokinin ribonucleotides in plant cells. The contrasting effects exerted by deoxyribonucleosides of isoprenoid (true hormonal activity) and aromatic (almost no activity) cytokinins indicates a significant difference in the biosynthesis of these compounds.

scholarly journals Structure and Biomechanics during Xylem Vessel Transdifferentiation in Arabidopsis thaliana

Plants ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 1715
Author(s):  
Eleftheria Roumeli ◽  
Leah Ginsberg ◽  
Robin McDonald ◽  
Giada Spigolon ◽  
Rodinde Hendrickx ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Cell Wall ◽  
Cell Walls ◽  
Turgor Pressure ◽  
Plant Cells ◽  
Building Blocks ◽  
Xylem Vessel ◽  
Primary Cell Wall ◽  
Individual Plant ◽  
Vessel Elements

Individual plant cells are the building blocks for all plantae and artificially constructed plant biomaterials, like biocomposites. Secondary cell walls (SCWs) are a key component for mediating mechanical strength and stiffness in both living vascular plants and biocomposite materials. In this paper, we study the structure and biomechanics of cultured plant cells during the cellular developmental stages associated with SCW formation. We use a model culture system that induces transdifferentiation of Arabidopsis thaliana cells to xylem vessel elements, upon treatment with dexamethasone (DEX). We group the transdifferentiation process into three distinct stages, based on morphological observations of the cell walls. The first stage includes cells with only a primary cell wall (PCW), the second covers cells that have formed a SCW, and the third stage includes cells with a ruptured tonoplast and partially or fully degraded PCW. We adopt a multi-scale approach to study the mechanical properties of cells in these three stages. We perform large-scale indentations with a micro-compression system in three different osmotic conditions. Atomic force microscopy (AFM) nanoscale indentations in water allow us to isolate the cell wall response. We propose a spring-based model to deconvolve the competing stiffness contributions from turgor pressure, PCW, SCW and cytoplasm in the stiffness of differentiating cells. Prior to triggering differentiation, cells in hypotonic pressure conditions are significantly stiffer than cells in isotonic or hypertonic conditions, highlighting the dominant role of turgor pressure. Plasmolyzed cells with a SCW reach similar levels of stiffness as cells with maximum turgor pressure. The stiffness of the PCW in all of these conditions is lower than the stiffness of the fully-formed SCW. Our results provide the first experimental characterization of the mechanics of SCW formation at single cell level.

scholarly journals The γ-tubulin complex protein GCP6 is crucial for spindle morphogenesis but not essential for microtubule reorganization inArabidopsis

2019 ◽  
Vol 116 (52) ◽  
pp. 27115-27123 ◽  
Author(s):  
Huiying Miao ◽  
Rongfang Guo ◽  
Junlin Chen ◽  
Qiaomei Wang ◽  
Yuh-Ru Julie Lee ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Vegetative Growth ◽  
Functional Form ◽  
Plant Cells ◽  
Wild Type ◽  
Gene Encoding ◽  
Small Complex ◽  
Complex Protein ◽  
Ring Complex ◽  
Insight Into

γ-Tubulin typically forms a ring-shaped complex with 5 related γ-tubulin complex proteins (GCP2 to GCP6), and this γ-tubulin ring complex (γTuRC) serves as a template for microtubule (MT) nucleation in plants and animals. While the γTuRC takes part in MT nucleation in most eukaryotes, in fungi such events take place robustly with just the γ-tubulin small complex (γTuSC) assembled by γ-tubulin plus GCP2 and GCP3. To explore whether the γTuRC is the sole functional γ-tubulin complex in plants, we generated 2 mutants of theGCP6gene encoding the largest subunit of the γTuRC inArabidopsis thaliana. Both mutants showed similar phenotypes of dwarfed vegetative growth and reduced fertility. Thegcp6mutant assembled the γTuSC, while the wild-type cells had GCP6 join other GCPs to produce the γTuRC. Although thegcp6cells had greatly diminished γ-tubulin localization on spindle MTs, the protein was still detected there. Thegcp6cells formed spindles that lacked MT convergence and discernable poles; however, they managed to cope with the challenge of MT disorganization and were able to complete mitosis and cytokinesis. Our results reveal that the γTuRC is not the only functional form of the γ-tubulin complex for MT nucleation in plant cells, and that γ-tubulin-dependent, but γTuRC-independent, mechanisms meet the basal need of MT nucleation. Moreover, we show that the γTuRC function is more critical for the assembly of spindle MT array than for the phragmoplast. Thus, our findings provide insight into acentrosomal MT nucleation and organization.

scholarly journals The HSP Terminator of Arabidopsis thaliana Increases Gene Expression in Plant Cells

2009 ◽  
Vol 51 (2) ◽  
pp. 328-332 ◽  
Author(s):  
Shingo Nagaya ◽  
Kazue Kawamura ◽  
Atsuhiko Shinmyo ◽  
Ko Kato
Keyword(s):  
Gene Expression ◽  
Arabidopsis Thaliana ◽  
Plant Cells
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