Biology subjects

Ndinyanka Fabrice, T.

Publications and source records attributed to Ndinyanka Fabrice, T..

3 recordsLinked to original sources

bioRxiv2021

Cell Wall Biochemistry Drives Pollen Tube Mechanics and Affects Growth Rate

Pollen tubes maintain cell wall integrity as they rapidly grow towards the ovule, yet need to rupture at a precise moment to release the sperm cells. This biomechanical balance is critical for fertilization and relies on the interplay between turgor pressure and cell wall rigidity. How cell wall composition affects its mechanical properties is, however, not well understood. In this study, we combine experimental and simulation techniques to determine key mechanical parameters using Arabidopsis cell wall mutants. We integrated cellular force microscopy with a Finite Element Method-based model to predict growth rates of different mutant pollen tubes. The Finite Element Method-based model allowed us to quantify the effects of cell wall mutations on the time-independent turgor pressure and cell wall elasticity, while cellular force microscopy enabled determination of time-dependent viscoelastic properties of the cell wall. This novel approach can be applied across biological systems and advances mechanical studies of cell and tissue morphogenesis.

systems 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↗

bioRxiv2017

LRX Proteins play a crucial role in pollen grain and pollen tube cell wall development

Leucine-rich repeat extensins (LRXs) are chimeric proteins containing an N-terminal leucine-rich repeat (LRR) and a C-terminal extensin domain. LRXs are involved in cell wall formation in vegetative tissues and required for plant growth. However, the nature of their role in these cellular processes remains to be elucidated. Here, we used a combination of molecular techniques, light microscopy, and transmission electron microscopy to characterize mutants of pollen-expressed LRXs in Arabidopsis thaliana. Mutations in multiple pollen-expressed lrx genes causes severe defects in pollen germination and pollen tube (PT) growth, resulting in a reduced seed set. Physiological experiments demonstrate that manipulating Ca2+ availability partially suppresses the PT growth defects, suggesting that LRX proteins influence Ca2+-related processes. Furthermore, we show that LRX protein localizes to the cell wall, and its LRR-domain (which likely mediates protein-protein interactions) is associated with the plasma membrane. Mechanical analyses by cellular force microscopy and finite element method-based modelling revealed significant changes in the material properties of the cell wall and the fine-tuning of cellular biophysical parameters in the mutants compared to the wild type. The results indicate that LRX proteins might play a role in cell wall-plasma membrane communication, influencing cell wall formation and cellular mechanics.

plant biology↗