Biology subjects

Andrey, P.

Publications and source records attributed to Andrey, P..

6 recordsLinked to original sources

bioRxiv2025

Actin Counters Geometry to Guide Plant Cell Division

In multicellular organisms, cell division shapes tissue architecture, cell identity, and function. In walled organisms like plants, division plane orientation irreversibly defines tissue topology and is tightly regulated. While divisions often follow the shortest path enclosing cell volume, certain cells deviate, dividing perpendicular to the growth axis. Tissue-scale mechanical stress has been proposed to guide such orientation, but how these cues are integrated remains unclear. Here, we re-examine the role of the actin cytoskeleton in orienting cell division in Arabidopsis root epidermis. Combining cell biology, genetics, pharmacological treatments, 3D segmentation, and modelling, we show that actin is a central molecular actor required to establish cell division orientation against the geometrical rules, highlighting its role in integrating spatial information.

plant biology↗

bioRxiv2025

Semi-automatic quantification of 3D Histone H3 phosphorylation signals during cell division in Arabidopsis root meristems

O_LIPosttranslational modification of histones during the cell cycle is a major process controlling many aspects of cell division. Among the variety of histone modifications, mitotic phosphorylation of histone H3 at serine 10 (H3S10ph) plays a crucial role, particularly in proper chromosome segregation. Here we aimed at precisely quantifying this phosphorylation dynamics during mitosis in plant cells, in order to reveal molecular pathways involved in this process. C_LIO_LIWe describe an analysis pipeline based on 3D image analysis that allows to semi-automatically quantify H3S10 phosphorylation in mitotic Arabidopsis root cells. We also developed a new method for the compensation of signal attenuation in Z, based on measurement of objects of interest themselves. C_LIO_LIWe show that this new attenuation correction method allows significant gains in accuracy and statistical power. Using this pipeline, we were able to reveal small H3S10ph differences between cells treated with hesperadin, an inhibitor of an H3S10ph kinase, or between Arabidopsis mutants affected in PP2A phosphatase activity. C_LIO_LIThis tool opens new avenues to explore such regulation pathway in plants, using the wealth of genetic material available in Arabidopsis. It can also be applied to study other histone post-translational modifications, and more generally to any discrete 3D signals. C_LI

cell biology↗

bioRxiv2024

The unusual orf117Sha locus causes desynchronization of pollen development in the Arabidopsis gametophytic Sha CMS

Cytoplasmic male sterility (CMS) is of major agronomical relevance in hybrid breeding. In gametophytic CMS, abortion of pollen is determined by the grain genotype, while in sporophytic CMS, it is determined by the mother plant genotype. While several CMS mechanisms have been dissected at the molecular level, gametophytic CMS has not been straightforwardly accessible. We used the gametophytic Sha-CMS in Arabidopsis to characterize the cause and process of pollen abortion by implementing in vivo biosensing in single pollen and mitoTALEN mutagenesis. We obtained conclusive evidence that orf117Sha is the CMS-causing gene, despite distinct characteristics from other CMS-genes. We measured the in vivo cytosolic ATP content in single pollen, followed pollen development and analyzed pollen mitochondrial volume in two genotypes that differed only by the presence of the orf117Sha locus. Our results show that the Sha-CMS is not triggered by ATP deficiency. Instead, we observed desynchronization of a pollen developmental program. Pollen death occurred independently in pollen grains at diverse stages and was preceded by mitochondrial swelling. We conclude that pollen death is grain-autonomous in Sha-CMS and propose that mitochondrial permeability transition, which was previously described as a hallmark of developmental and environmental-triggered cell death programs, precedes pollen death in Sha-CMS. HighlightThe Arabidopsis CMS-causing gene orf117Sha does not limit pollen ATP supply. Pollen-centered approaches show desynchronization of development and mitochondrial swelling before pollen death, which occurred at diverse stages.

plant biology↗

bioRxiv2023

Rapid meiotic prophase chromosome movements in Arabidopsis thaliana are linked to essential reorganization at the nuclear envelope

Meiotic rapid prophase chromosome movements (RPMs) require connections between the chromosomes and the cytoskeleton, involving SUN (Sad1/UNC-84)-domain-containing proteins at the inner nuclear envelope (NE). RPMs remain significantly understudied in plants, notably with respect to their importance in the regulation of meiosis. Here, we demonstrate that Arabidopsis thaliana meiotic centromeres undergo rapid (up to 500 nm/s) and uncoordinated movements during the zygotene and pachytene stages. RPMs are not affected by altered chromosome organization and recombination but are abolished in the double mutant sun1 sun2. We also document the changes in chromosome dynamics and nucleus organization during the transition from leptotene to zygotene, including telomere attachment to SUN-enriched NE domains, bouquet formation, and nucleolus displacement, all of which were defective in sun1 sun2. These results establish A. thaliana as a new model species for studying the functional implications of meiotic RPMs and demonstrate the mechanistic conservation of telomere-led RPMs in plants.

genetics↗

bioRxiv2022

Spatial modeling of telomere intra-nuclear distribution reveals non-random organization that varies during cell cycle and depends on LAP2 and BAF

Genome organization within the 3D nuclear volume influences major biological processes but is completely lost during mitosis, which represents a major challenge to maintain cellular identity and cell fate. To restore a functional G1 nucleus for the next cell cycle, it is imperative to reestablish genome organization during post-mitotic nuclear assembly. Importantly, the configuration of linear chromosomes has been shown to directly impact spatial genome architecture. Both centromeres and telomeres are known to associate with nuclear structures, such as the nuclear envelope, and support chromatin distribution. Here, using high-resolution 3D imaging combined with 3D spatial statistics and modeling, we showed that telomeres generally followed a regular distribution compared to what is expected under a random organization. While the preferential localization of telomeres at nuclear periphery was restricted to early G1, we found a strong clustering of centromeres in addition to their predominant peripheral localization at all cell cycle stages. We then conducted a targeted screen using MadID to identify the molecular pathways driving or maintaining telomere anchoring to the nuclear envelope. Among these factors, we could show that LAP2 transiently localizes to telomeres in anaphase, at a stage where LAP2 initiates the reformation of the nuclear envelope. Moreover, co-depletion of LAP proteins and their partner BAF impacted telomere redistribution in the next interphase. There results suggest that in addition to their crucial role in genome protection, telomeres also participate in reshaping functional G1 nuclei after mitosis.

cell biology↗

bioRxiv2022

Large-scale analysis and computer modeling reveal hidden regularities behind variability of cell division patterns in Arabidopsis thaliana embryogenesis

Noise plays a major role in cellular processes and in the development of tissues and organs. Several studies have examined the origin, the integration or the accommodation of noise in gene expression, cell growth and elaboration of organ shape. By contrast, much less is known about variability in cell division plane positioning, its origin and links with cell geometry, and its impact on tissue organization. Taking advantage of the first-stereotyped-then-variable division patterns in the embryo of the model plant Arabidopsis thaliana, we combined 3D imaging and quantitative cell shape and cell lineage analysis together with mathematical and computer modeling to perform a large scale, systematic analysis of variability in division plane orientation. Our results reveal that, paradoxically, variability in cell division patterns of Arabidopsis embryos is accompanied by a progressive reduction of cell shape heterogeneity. The paradox is solved by showing that variability operates within a reduced repertoire of possible division plane orientations that is related to cell geometry. We show that in several domains of the embryo, a recently proposed geometrical division rule recapitulates observed variable patterns, thus suggesting that variable patterns emerge from deterministic principles operating in a variable geometrical context. Our work highlights the importance of emerging patterns in the plant embryo under iterated division principles, but also reveal domains where deviations between rule predictions and experimental observations point to additional regulatory mechanisms.

developmental biology↗