Single-Particle Tracking of Genetically Encoded Multimeric Nanoparticles Reveals Regional Heterogeneity and Osmotic Stress-Induced Convergence of Cytoplasmic Crowding in Plant Root Cells

Abstract

Abstract Macromolecular crowding is a fundamental physical property of the cytoplasm that governs intracellular diffusion and biochemical reactions. However, in situ quantitative characterization of intracellular dynamics and associated biophysical states in intact plant tissues remains challenging. Using 40-nm genetically encoded multimeric nanoparticles (GEMs) and single-particle tracking in Arabidopsis roots, we quantitatively map the regional heterogeneity of cytoplasmic diffusion dynamics and crowding along the root developmental axis: elongation zone cells exhibit a dense, low-mobility baseline, whereas maturation zone and root hair cells display higher mobility. These regions exhibit different sensitivities to osmotic stress. Notably, under severe ionic stress, both the diffusion coefficients and non-Gaussian parameters of the maturation zone and root hair cells converge toward the levels of the elongation zone cells, suggesting an intrinsic physical baseline for cytoplasmic crowding. This kinetic convergence in these cells is accompanied by vacuolar retraction and an increase in cytoplasmic thickness. Together, our study establishes a GEMs-based platform for in situ biophysical analysis in plant cells and uncovers a spatially-resolved physical landscape of cytoplasmic crowding and its dynamic reorganization under osmotic stress.

Plant phenotyping relevance

植物細胞内の拡散動態・細胞質クラウディングを定量するGEMs単粒子追跡法を構築し、植物根で実証した研究であり、表現型取得基盤が中心である。

Code and data availability

The supplied article blocks contain no public phenotype/trait datasets, imaging data, analysis code, or trained models. The paper describes GEMs single-particle tracking in Arabidopsis roots, but no data or code availability statement, repository name, or URL appears anywhere in the supplied text, and allowed_urls is空.

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