Biology subjects

Peters, W. S.

Publications and source records attributed to Peters, W. S..

3 recordsLinked to original sources

bioRxiv2024

Anatomics MLT, an AI tool for large scale quantification of ultrastructural traits

The ever increasing breadth of biological knowledge has led to recent efforts to combine information from various fields into cell- or tissue atlases. Anatomical features are the structural basis for such efforts, but unfortunately large scale analysis of subcellular anatomical traits is currently a missing feature. Similarly, small phenotypic alterations of organelle- or cell-specific anatomical traits, such as an increase of the total volume or the number of mitochondria in response to certain stimuli, are currently hard to quantify. To provide tools to extract quantitative information from available 3D microscopic datasets generated with methods such as serial block face scanning electron microscopy we a) developed much improved fixation and embedding protocols for plants to drastically reduce processing artifacts and b) generated an easy-to-use AI tool for quantitative analysis and visualization of large-scale data sets. We make this tool available as open source.

cell biology↗

bioRxiv2024

Electric charge controls plasmodesma conductivity

While plant cells are enclosed by rigid cell walls that counteract intracellular hydrostatic pressure1, their plasma membrane, cytosol, and endoplasmic reticulum (ER) remain connected through plasmodesmata, nanoscopic cell wall pores2. Plasmodesmal cell-to-cell transport occurs in the cytosolic sleeve between the plasma membrane and the ER membrane3-5, and is generally thought to be limited by the size of the moving particle alone6. Given that biological membranes carry negative electric surface charges7-9, this steric notion conflicts with physical theory of ion diffusion in nanometer-sized pores with charged walls10. Quantifying the movements of differently sized and charged fluorescent dyes in Tradescantia stamen hairs, we found that anionic fluorophores of up to 1 kDa traversed plasmodesmata whereas much smaller cationic ones did not. While this agrees with theoretical expectations of different size exclusion limits for cations and anions, it questions current dogma concerning plasmodesma function and also structure, as it implies positively rather than negatively charged surfaces within plasmodesmal pores. Our findings call for re-evaluations of current models of symplasmic transport, especially of charged molecules like the phytohormone auxin (indole-acetic acid) and certain amino acids.

cell biology↗

bioRxiv2021

Diversity of funnel plasmodesmata in angiosperms: the impact of geometry on plasmodesmal resistance

In most plant tissues, threads of cytoplasm, or plasmodesmata, connect the protoplasts via pores in the cell walls. This enables symplasmic transport, for instance in phloem loading, transport, and unloading. Importantly, the geometry of the wall pore limits the size of the particles that may be transported, and also (co-)defines plasmodesmal resistance to diffusion and convective flow. However, quantitative information on transport through plasmodesmata in non-cylindrical cell wall pores is scarce. We have found conical, funnel-shaped cell wall pores in the phloem-unloading zone in growing root tips of five eudicot and two monocot species, specifically between protophloem sieve elements and phloem pole pericycle cells. 3D reconstructions by electron tomography suggested that funnel plasmodesmata possess a desmotubule but lack tethers to fix it in a central position. Model calculations showed that both diffusive and hydraulic resistance decrease drastically in conical cell wall pores compared to cylindrical channels, even at very small opening angles. Notably, the effect on hydraulic resistance was relatively larger. We conclude that funnel plasmodesmata generally are present in specific cell-cell interfaces in angiosperm roots, where they appear to facilitate symplasmic phloem unloading. Interestingly, cytosolic sleeves of most plasmodesmata reported in the literature do not resemble straight annuli but possess variously shaped widenings. Our evaluations suggest that widenings too small for identification on electron micrographs may drastically reduce the hydraulic and diffusional resistance of these pores. Consequently, theoretical models assuming cylindrical symmetries will underestimate plasmodesmal conductivities.

plant biology↗