Biology subjects

Rutowicz, K.

Publications and source records attributed to Rutowicz, K..

4 recordsLinked to original sources

bioRxiv2025

Linker Histones Enhance Robustness in Diurnal Transcription Dynamics.

Linker histone H1 is crucial for chromatin organization and gene expression in Arabidopsis thaliana, influencing development and stress responses. To explore its role in diurnal gene regulation, we examined H1-deficient plants and found that H1 is essential for maintaining rhythmic gene expression. Genes losing synchronization often contained NAC transcription factor binding sites, indicating H1 may affect their accessibility. Nuclear imaging revealed that H1 subtly modulates nuclear size and chromatin distribution across the photoperiod. Epigenetic analysis showed typical diurnal changes--declines in H3K4me3 and active RNA Pol II in the evening and increases in H3K27me3. In H1 mutants, these patterns persisted but with elevated H3K4me3 and RNA Pol II (Ser2P) levels at night and in the morning. These results suggest that H1 fine-tunes chromatin and transcriptional rhythms, contributing to the temporal coordination of gene activity in response to environmental and developmental signals.

plant biology↗

bioRxiv2025

A citrullination-ubiquitination pathway controls pre-meiotic H1 eviction and is essential for gametogenesis in Arabidopsis

Despite being evolutionary distant, plants and animals share a common phenomenon at the somatic-to-reproductive cell fate transition with extensive structural and compositional changes in chromatin. Such chromatin reprogramming occurs in the plant SMCs (Spore Mother Cells) and animal PGCs (primordial germ cells) and is initiated by the loss of linker histones (H1). H1 loss is essential to establish pluripotency in animal PGCs but its role is not known in plants. Here, we identified two regulatory pathways involving a citrullinase and an E3-ubiquitin ligase that contribute H1.1 loss in female SMC in Arabidopsis. We also identified roles for two specific residues: an arginine, whose positive charge contributes to H1.1 destabilization from chromatin, and a lysine in the globular domain that is essential for H1.1 degradation. Ovules with impaired H1.1 loss in the SMC proceed through sporogenesis but fail to complete gametogenesis. We propose a citrullination-ubiquitination pathway governing pre-meiotic H1 depletion as a critical mechanism for establishing post-meiotic competence in the Arabidopsis germline.

plant biology↗

bioRxiv2023

Multiscale chromatin dynamics and high entropy in plant iPSC cultures

Plant protoplasts constitute the starting material to induce pluripotent cell masses in vitro competent for tissue regeneration. Dedifferentiation is associated with large-scale chromatin reorganisation and massive transcriptome reprogramming, characterized by stochastic gene expression. How this cellular variability reflects on chromatin organisation in individual cells and what are the factors influencing chromatin transitions during culturing is largely unknown. High-throughput imaging and a custom, supervised image analysis protocol extracting over 100 chromatin features unravelled a rapid, multiscale dynamics of chromatin patterns which trajectory strongly depends on nutrients availability. Decreased abundance in H1 (linker histones) is hallmark of chromatin transitions. We measured a high heterogeneity of chromatin patterns indicating an intrinsic entropy as hallmark of the initial cultures. We further measured an entropy decline over time, and an antagonistic influence by external and intrinsic factors, such as phytohormones and epigenetic modifiers, respectively. Collectively, our study benchmarks an approach to understand the variability and evolution of chromatin patterns underlying plant cell reprogramming in vitro.

molecular biology↗

bioRxiv2018

Linker histones regulate fine-scale chromatin organization and modulate developmental decisions in Arabidopsis

Chromatin in eukaryotes provides a tunable platform to control gene expression and convey an epigenetic memory throughout cell divisions. H1 linker histones are abundant components with an intrinsic potential in influencing chromatin structure and function. We detail the impact of H1 depletion in Arabidopsis on fine-scale chromatin organization, transcription and development. While required for chromocenter assembly, H1s are dispensable for transposable element (TE) silencing and peripheral positioning of heterochromatin. In euchromatin, H1 regulates nucleosome density, mobility, and regular distribution of nanoscale chromatin domains. While necessary to maintain epigenetic patterns, H1 only moderately affects transcription. Its depletion is associated with failures in transitional fate changes such as lateral root initiation, root hair production, stomata patterning but also flowering and dormancy regulation. Therefore, Arabidopsis H1 variants are chromatin architects mediating nano- and microscale levels-of-organization operating downstream of epigenetic and transcriptional establishment processes and contribute to epigenetic reorientations in developmental transitions.

molecular biology↗