Biology subjects

Burda, I.

Publications and source records attributed to Burda, I..

3 recordsLinked to original sources

bioRxiv2025

ROS inhibits microtubule dynamics and cell growth heterogeneity during Arabidopsis sepal morphogenesis

Developing organs grow to reproducible sizes and shapes yet the growth of their constituent cells can be highly heterogeneous and fluctuating. During wild-type Arabidopsis thaliana sepal development, the fluctuations in cell growth average such that the sepals grow to uniform sizes and shapes. The uniform size and shape of the sepals allow the flower bud to stay closed and protected until the floral organs are mature. In contrast, cell growth averaging is reduced in the ftsh4-5 mutant, and the sepals develop to variable sizes and shapes. FTSH4 encodes a mitochondrial i-AAA protease localized to the mitochondria. Reactive oxygen species (ROS) accumulate in ftsh4-5 mutants, and lowering ROS levels rescues the sepal size and shape variability. Here, we investigate the effects of ROS on cell growth heterogeneity and cortical microtubule dynamics. We find that elevated ROS suppresses cell growth heterogeneity and averaging. We also find that elevated ROS causes cortical microtubules to become more crisscrossed, as well as more stable. The growth of the cells with crisscrossed microtubules changes less in time, which impairs cell growth averaging. However, depolymerizing microtubules is insufficient to restore normal growth fluctuations. Altogether, our results suggest that ROS affects microtubule dynamics and cell growth fluctuations which are necessary for robust morphogenesis.

developmental biology↗

bioRxiv2024

Mechanical properties are tuned during development with the fibrous network nature of the Arabidopsis cell wall

During plant development, the mechanical properties of the cell walls must be tuned to regulate the growth of the cells. Cell growth involves significant stretching of the cell walls, yet little is known about the mechanical properties of cell walls under such substantial deformation, or how these mechanical properties change to regulate development. Here, we investigated the mechanical behavior of the Arabidopsis leaf epidermal cells being stretched. We found that the mechanical properties arise from the cell wall, which behaves as a fibrous network material. The epidermis exhibited a non-linear stiffening behavior that fell into three regimes. Each regime corresponded to distinct nonlinear behaviors in terms of transverse deformation (i.e., Poisson effect) and unrecoverable deformation (i.e., plasticity). Using a model, we demonstrated that the transition from reorientation and bending-dominated to stretch-dominated deformation modes of cellulose microfibrils cause these nonlinear behaviors. We found the stiffening behavior is more pronounced at later developmental stages. Finally, we show the spiral2-2 mutant has anisotropic mechanical properties, likely contributing to the spiraling of leaves. Our findings reveal the fibrous network nature of cell walls gives a high degree of tunability in mechanical properties, which allows cells to adjust these properties to support proper development.

plant biology↗

bioRxiv2023

Robust organ size in Arabidopsis is primarily governed by cell growth rather than cell division patterns

Organ sizes and shapes are highly reproducible, or robust, within a species and individuals. Arabidopsis thaliana sepals, which are the leaf-like organs that enclose flower buds, have consistent size and shape, which indicates robust development. Counterintuitively, variability in cell growth rate over time and between cells facilitates robust development because cumulative cell growth averages to a uniform rate. Here we investigate how sepal morphogenesis is robust to changes in cell division but not robust to changes in cell growth variability. We live image and quantitatively compare the development of sepals with increased or decreased cell division rate (lgo mutant and LGO overexpression, respectively), a mutant with altered cell growth variability (ftsh4), and double mutants combining these. We find that robustness is preserved when cell division rate changes because there is no change in the spatial pattern of growth. Meanwhile when robustness is lost in ftsh4 mutants, cell growth accumulates unevenly, and cells have disorganized growth directions. Thus, we demonstrate in vivo that both cell growth rate and direction average in robust development, preserving robustness despite changes in cell division. Summary statementRobust sepal development is preserved despite changes in cell division rate and is characterized by spatiotemporal averaging of heterogeneity in cell growth rate and direction.

plant biology↗