Biology subjects

Maugarny-Cales, A.

Publications and source records attributed to Maugarny-Cales, A..

3 recordsLinked to original sources

bioRxiv2025

Replication-independent eviction of H2B.8 reveals chromatin reprogramming during seed imbibition

The transition from seed to seedling involves major changes in nuclear organization and gene expression, yet the extent to which this developmental transition requires chromatin reprogramming remains largely unexplored. Here, we report that Arabidopsis dry seed embryos accumulate the histone variant H2B.8, which contributes to higher-order chromatin organization by forming spatial clusters that structure the 3D nuclear space. H2B.8 forms heterotypic nucleosomes at euchromatic transposons and lowly expressed genes and, during imbibition, modulates the transcriptional activation of a subset of these genes. Imbibition triggers a decrease in H2B.8 transcripts and the eviction of H2B.8 proteins in a process that operates independently of DNA replication but requires protein translation and de novo transcription. Histone eviction is not limited to H2B.8 as imbibition also induces the turnover of the H3.3 histone variant, thereby initiating a broad, replication-independent chromatin reprogramming process. These findings highlight a fundamental mechanism of epigenetic regulation during early plant development.

molecular biology↗

bioRxiv2022

De novo stem cell establishment in meristems requires repression of organ boundary cell fate

Stem cells play important roles in animal and plant biology as they sustain morphogenesis and tissue replenishment following aging or injuries. In plants, stem cells are embedded in multicellular structures called meristems and the formation of new meristems is essential for the plastic expansion of the highly branched shoot and root systems. In particular, axillary meristems that produce lateral shoots arise from the division of boundary domain cells at the leaf base. The CUP-SHAPED COTYLEDON (CUC) genes are major determinants of the boundary domain and are required for axillary meristem initiation. However, how axillary meristems get structured and how stem cells become established de novo remains elusive. Here, we show that two NGATHA-LIKE transcription factors, DPA4 and SOD7, redundantly repress CUC expression in the initiating axillary meristem. Ectopic boundary fate leads to abnormal growth and organisation of the axillary meristem and prevents de novo stem cell establishment. Floral meristems of the dpa4 sod7 double mutant show a similar delay in stem cell de novo establishment. Altogether, while boundary fate is required for the initiation of axillary meristems, our work reveals how it is later repressed to allow proper meristem establishment and de novo stem cell niche formation.

plant biology↗

bioRxiv2020

Frizzled-dependent Planar Cell Polarity without Wnt Ligands

Planar cell polarity (PCP) organizes the orientation of cellular protrusions and migratory activity within the tissue plane. PCP establishment involves the subcellular polarization of core PCP components. It has been suggested Wnt gradients could provide a global cue that coordinates local PCP with tissue axes. Here we dissect the role of Wnt ligands in the orientation of hairs of Drosophila wings, an established system for study of PCP. We found that PCP was normal in quintuple mutant wings that rely solely on membrane-tethered Wingless for Wnt signaling, suggesting that a Wnt gradient is not required. We then used a nanobody-based approach to trap Wntless in the endoplasmic reticulum, and hence prevent all Wnt secretion, specifically during the period of PCP establishment. PCP was still established. We conclude that, even though Wnt ligands could contribute to PCP, they are not essential, and another global cue must exist for tissue-wide polarization.

developmental biology↗