Meiosis as a mechanism for epigenetic reprogramming and cellular rejuvenation.

Meiosis is a hallmark of sexual reproduction because it represents the transition from one life cycle to the next and, in animals, meiosis produces gametes. Why meiosis evolved has been debated and most studies have focused on recombination of the parental alleles as the main function of meiosis. However, 40 years ago, Robin Holliday proposed that an essential function of meiosis is to oppose the consequence of successive mitoses that cause cellular aging.

Molecular and structural basis of the chromatin remodeling activity by Arabidopsis DDM1.

The histone H2A variant H2A.W occupies transposons and thus prevents access to them in Arabidopsis thaliana. H2A.

Two imprinted genes primed by DEMETER in the central cell and activated by WRKY10 in the endosperm.

The early development of the endosperm is crucial for balancing the allocation of maternal nutrients to offspring. This process is believed to be evolutionarily associated with genomic imprinting, resulting in parentally biased allelic gene expression. Beyond FertilizationIndependentSeed (FIS) genes, the number of imprinted genes involved in early endosperm development and seed size determination remains limited.

The Chaperone NASP Contributes to de Novo Deposition of the Centromeric Histone Variant CENH3 in Arabidopsis Early Embryogenesis.

The centromere is an essential chromosome region where the kinetochore is formed to control equal chromosome distribution during cell division. The centromere-specific histone H3 variant CENH3 (also called CENP-A) is a prerequisite for the kinetochore formation. Since CENH3 evolves rapidly, associated factors, including histone chaperones mediating the deposition of CENH3 on the centromere, are thought to act through species-specific amino acid sequences.

Identification of plants' functional counterpart of the metazoan mediator of DNA Damage checkpoint 1.

Induction of DNA damage triggers rapid phosphorylation of the histone H2A.X (γH2A.X).

Micropillar arrays, wide window acquisition and AI-based data analysis improve comprehensiveness in multiple proteomic applications.

Comprehensive proteomic analysis is essential to elucidate molecular pathways and protein functions. Despite tremendous progress in proteomics, current studies still suffer from limited proteomic coverage and dynamic range. Here, we utilize micropillar array columns (µPACs) together with wide-window acquisition and the AI-based CHIMERYS search engine to achieve excellent proteomic comprehensiveness for bulk proteomics, affinity purification mass spectrometry and single cell proteomics.

Plant reproduction: Ancient origins of male germline differentiation.

Despite the wide diversity in male sexual development across land plants, new work reveals the conservation of a heterodimer of transcription factors as master regulators of the male germline.

Paternal imprinting in Marchantia polymorpha.

We are becoming aware of a growing number of organisms that do not express genetic information equally from both parents as a result of an epigenetic phenomenon called genomic imprinting. Recently, it was shown that the entire paternal genome is repressed during the diploid phase of the life cycle of the liverwort Marchantia polymorpha. The deposition of the repressive epigenetic mark H3K27me3 on the male pronucleus is responsible for the imprinted state, which is reset by the end of meiosis.

The chromatin source-sink hypothesis: a shared mode of chromatin-mediated regulations.

We propose that several chromatin-mediated regulatory processes are dominated by source-sink relationships in which factors operate as 'sources' to produce or provide a resource and compete with each other to occupy separate 'sinks'. In this model, large portions of genomic DNA operate as 'sinks', which are filled by 'sources', such as available histone variants, covalent modifications to histones, the readers of these modifications and non-coding RNAs. Competing occupation for the sinks by different sources leads to distinct states of genomic equilibrium in differentiated cells.

The ancestral chromatin landscape of land plants.

Recent studies have shown that correlations between chromatin modifications and transcription vary among eukaryotes. This is the case for marked differences between the chromatin of the moss Physcomitrium patens and the liverwort Marchantia polymorpha. Mosses and liverworts diverged from hornworts, altogether forming the lineage of bryophytes that shared a common ancestor with land plants.

Cell cycle status of male and female gametes during Arabidopsis reproduction.

Fertilization in Arabidopsis (Arabidopsis thaliana) is a highly coordinated process that begins with a pollen tube delivering the 2 sperm cells into the embryo sac. Each sperm cell can then fertilize either the egg or the central cell to initiate embryo or endosperm development, respectively. The success of this double fertilization process requires a tight cell cycle synchrony between the male and female gametes to allow karyogamy (nuclei fusion).

The Polycomb repressive complex 2 deposits H3K27me3 and represses transposable elements in a broad range of eukaryotes.

The mobility of transposable elements (TEs) contributes to evolution of genomes. Their uncontrolled activity causes genomic instability; therefore, expression of TEs is silenced by host genomes. TEs are marked with DNA and H3K9 methylation, which are associated with silencing in flowering plants, animals, and fungi.

Histone variants shape chromatin states in Arabidopsis.

How different intrinsic sequence variations and regulatory modifications of histones combine in nucleosomes remain unclear. To test the importance of histone variants in the organization of chromatin we investigated how histone variants and histone modifications assemble in the genome. We showed that a limited number of chromatin states divide euchromatin and heterochromatin into several subdomains.

Variation is important: Warranting chromatin function and dynamics by histone variants.

The chromatin of flowering plants exhibits a wide range of sequence variants of the core and linker histones. Recent studies have demonstrated that specific histone variant enrichment, combined with post-translational modifications (PTMs) of histones, defines distinct chromatin states that impact specific chromatin functions. Chromatin remodelers are emerging as key regulators of histone variant dynamics, contributing to shaping chromatin states and regulating gene transcription in response to environment.

Cellular dynamics of coenocytic endosperm development in Arabidopsis thaliana.

After double fertilization, the endosperm in the seeds of many flowering plants undergoes repeated mitotic nuclear divisions without cytokinesis, resulting in a large coenocytic endosperm that then cellularizes. Growth during the coenocytic phase is strongly associated with the final seed size; however, a detailed description of the cellular dynamics controlling the unique coenocytic development in flowering plants has remained elusive. By integrating confocal microscopy live-cell imaging and genetics, we have characterized the entire development of the coenocytic endosperm of Arabidopsis thaliana including nuclear divisions, their timing intervals, nuclear movement and cytoskeleton dynamics.

Elongation factor 1 is a component of the Arabidopsis RNA polymerase II elongation complex and associates with a subset of transcribed genes.

Elongation factors modulate the efficiency of mRNA synthesis by RNA polymerase II (RNAPII) in the context of chromatin, thus contributing to implement proper gene expression programmes. The zinc-finger protein elongation factor 1 (ELF1) is a conserved transcript elongation factor (TEF), whose molecular function so far has not been studied in plants. Using biochemical approaches, we examined the interaction of Arabidopsis ELF1 with DNA and histones in vitro and with the RNAPII elongation complex in vivo.

Histone H3.3 deposition in seed is essential for the post-embryonic developmental competence in Arabidopsis.

The acquisition of germination and post-embryonic developmental ability during seed maturation is vital for seed vigor, an important trait for plant propagation and crop production. How seed vigor is established in seeds is still poorly understood. Here, we report the crucial function of Arabidopsis histone variant H3.

Polycomb-mediated repression of paternal chromosomes maintains haploid dosage in diploid embryos of .

Complex mechanisms regulate gene dosage throughout eukaryotic life cycles. Mechanisms controlling gene dosage have been extensively studied in animals, however it is unknown how generalizable these mechanisms are to diverse eukaryotes. Here, we use the haploid plant to assess gene dosage control in its short-lived diploid embryo.

The renaissance and enlightenment of Marchantia as a model system.

The liverwort Marchantia polymorpha has been utilized as a model for biological studies since the 18th century. In the past few decades, there has been a Renaissance in its utilization in genomic and genetic approaches to investigating physiological, developmental, and evolutionary aspects of land plant biology. The reasons for its adoption are similar to those of other genetic models, e.

Phosphorylation of the FACT histone chaperone subunit SPT16 affects chromatin at RNA polymerase II transcriptional start sites in Arabidopsis.

The heterodimeric histone chaperone FACT, consisting of SSRP1 and SPT16, contributes to dynamic nucleosome rearrangements during various DNA-dependent processes including transcription. In search of post-translational modifications that may regulate the activity of FACT, SSRP1 and SPT16 were isolated from Arabidopsis cells and analysed by mass spectrometry. Four acetylated lysine residues could be mapped within the basic C-terminal region of SSRP1, while three phosphorylated serine/threonine residues were identified in the acidic C-terminal region of SPT16.

One residue-one function.

The histone H3.1 variant deposited at replication forks docks DNA repair machinery.

Seminars in cell and development biology on histone variants remodelers of H2A variants associated with heterochromatin.

Variants of the histone H2A occupy distinct locations in the genome. There is relatively little known about the mechanisms responsible for deposition of specific H2A variants. Notable exceptions are chromatin remodelers that control the dynamics of H2A.

Which field of research would Gregor Mendel choose in the 21st century?

Gregor Mendel's work on segregation of traits in plants established the basic methodology and rules of genetics. The interruption of Mendel's research activities in 1870 impeded the immediate recognition of the value of his work until the dawn of the 20th century. Only then were his founding laws of genetics validated, propelling the development of biological research toward the birth of molecular biology in the second half of the 20th century.