Polo, C. C. | Search bioRxiv

bioRxiv2026

Three-dimensional nano-imaging reveals subtle changes in xylem structure in CAD-deficient sorghum

Lignin plays a central role in the formation and function of secondary cell walls in vascular plants. However, the structural consequences of lignin modification for cell wall properties and cellular function in grasses remain poorly understood. Here, we investigated how cinnamyl alcohol dehydrogenase (CAD) deficiency alters vascular cell architecture in Sorghum bicolor, using the brown midrib-6 (bmr6) mutant as a model system. Biochemical and histochemical analyses confirmed altered lignin chemistry in bmr6, including increased incorporation of hydroxycinnamaldehyde residues and reduced tricin levels. We applied ptychographic X-ray computed tomography (PXCT) to quantify the cell wall geometry, in three dimensions, at nanometer-scale resolution. PXCT enabled measurements of wall thickness distribution and lumen shape along tracheary elements. Analyses revealed no significant differences in wall thickness between wild-type and bmr6 plants. However, three-dimensional morphometric descriptors indicated reduced lumen convexity in bmr6, suggesting localized modifications not detectable by conventional two-dimensional imaging. Water flow numerical simulations through PXCT-derived images indicated reduced vessel permeability and simulated hydraulic conductivity in bmr6, suggesting that subtle geometric changes may influence performance. These findings highlight the value of three-dimensional imaging for resolving cell wall organization and provide new insight into the architectural resilience of grass xylem in response to targeted lignin modification. HighlightThree-dimensional X-ray nano-imaging reveals alterations in the cell wall architecture that affect simulated hydraulic performance under reduced CAD activity in sorghum.

plant biology↗

bioRxiv2026

Correlative Synchrotron X-ray Microscopy Reveals Dose- and Division-Dependent Nanoparticle Redistribution in Macrophages

Understanding the intracellular fate of nanoparticles is essential for designing safer and more effective nanomedicines, yet most studies rely on static observations and lack high-resolution, near-native volumetric information. Here, we establish a synchrotron-based correlative X-ray microscopy framework to investigate how fluorescent silica nanoparticles (SiNPs) redistribute within macrophages as a function of concentration and successive cell-division cycles. SiNPs were internalized by RAW 264.7 macrophages at different concentrations and analyzed using a synchrotron-based correlative X-ray microscopy workflow integrating cryogenic soft X-ray tomography (cryo-SXT), cryogenic structured illumination microscopy (cryo-SIM), and coherent X-ray ptychography, with confocal fluorescence microscopy used to establish population-level uptake tendencies. Cryo-SXT reveals a concentration-dependent redistribution of nanoparticle-containing vesicles from peripheral endosomes toward the perinuclear region, while correlative cryo-SIM confirms strict vesicular confinement, with no evidence of free nanoparticle diffusion into the nucleoplasm. At higher doses, nanoparticles approach the nuclear region via vesicles extending into nuclear-envelope invaginations, rather than by true nuclear entry. Successive cell divisions redistribute the intracellular nanoparticle load and promote stable perinuclear clustering, identifying a long-term sequestration route in macrophages. Coherent X-ray ptychography further reveals nanoscale deformations of the nuclear envelope associated with dense perinuclear vesicles. Together, these results establish synchrotron-based correlative X-ray microscopy as a mechanistic, multiscale platform for unveiling the dynamic intracellular fate of nanoparticles and providing mechanistic insight into their apparent nuclear localization.

cell biology↗