Cryo-electron tomography of the onion cell wall shows bimodally oriented cellulose fibers and reticulated homogalacturonan networks

article Cryo-electron tomography of the onion cell wall shows bimodally oriented cellulose fibers and reticulated homogalacturonan networks published yes William J. Nicolas author Florian Fäßler author 404F5528-F248-11E8-B48F-1D18A9856A870000-0001-7149-769X Przemysław Dutka author Florian KM Schur author 48AD8942-F248-11E8-B48F-1D18A9856A870000-0003-4790-8078 Grant Jensen author Elliot Meyerowitz author FlSc department Structure and isoform diversity of the Arp2/3 complex project One hallmark of plant cells is their cell wall. They protect cells against the environment and high turgor and mediate morphogenesis through the dynamics of their mechanical and chemical properties. The walls are a complex polysaccharidic structure. Although their biochemical composition is well known, how the different components organize in the volume of the cell wall and interact with each other is not well understood and yet is key to the wall’s mechanical properties. To investigate the ultrastructure of the plant cell wall, we imaged the walls of onion (Allium cepa) bulbs in a near-native state via cryo-focused ion beam milling (cryo-FIB milling) and cryo-electron tomography (cryo-ET). This allowed the high-resolution visualization of cellulose fibers in situ. We reveal the coexistence of dense fiber fields bathed in a reticulated matrix we termed “meshing,” which is more abundant at the inner surface of the cell wall. The fibers adopted a regular bimodal angular distribution at all depths in the cell wall and bundled according to their orientation, creating layers within the cell wall. Concomitantly, employing homogalacturonan (HG)-specific enzymatic digestion, we observed changes in the meshing, suggesting that it is—at least in part—composed of HG pectins. We propose the following model for the construction of the abaxial epidermal primary cell wall: the cell deposits successive layers of cellulose fibers at −45° and +45° relative to the cell’s long axis and secretes the surrounding HG-rich meshing proximal to the plasma membrane, which then migrates to more distal regions of the cell wall. https://research-explorer.ista.ac.at/download/11351/11730/2022_CurrentBiology_Nicolas.pdf application/pdfno Elsevier2022 eng General Agricultural and Biological SciencesGeneral BiochemistryGenetics and Molecular Biology Current Biology 0960-9822 35508170 00082239920001910.1016/j.cub.2022.04.024 3211P2375-2389 W. J. Nicolas, F. Fäßler, P. Dutka, F. K. Schur, G. Jensen, and E. Meyerowitz, “Cryo-electron tomography of the onion cell wall shows bimodally oriented cellulose fibers and reticulated homogalacturonan networks,” Current Biology, vol. 32, no. 11. Elsevier, pp. P2375-2389, 2022. Nicolas, William J., et al. “Cryo-Electron Tomography of the Onion Cell Wall Shows Bimodally Oriented Cellulose Fibers and Reticulated Homogalacturonan Networks.” Current Biology, vol. 32, no. 11, Elsevier, 2022, pp. P2375-2389, doi:<a href="https://doi.org/10.1016/j.cub.2022.04.024">10.1016/j.cub.2022.04.024</a>. Nicolas WJ, Fäßler F, Dutka P, Schur FK, Jensen G, Meyerowitz E. Cryo-electron tomography of the onion cell wall shows bimodally oriented cellulose fibers and reticulated homogalacturonan networks. Current Biology. 2022;32(11):P2375-2389. doi:<a href="https://doi.org/10.1016/j.cub.2022.04.024">10.1016/j.cub.2022.04.024</a> Nicolas, William J., Florian Fäßler, Przemysław Dutka, Florian KM Schur, Grant Jensen, and Elliot Meyerowitz. “Cryo-Electron Tomography of the Onion Cell Wall Shows Bimodally Oriented Cellulose Fibers and Reticulated Homogalacturonan Networks.” Current Biology. Elsevier, 2022. <a href="https://doi.org/10.1016/j.cub.2022.04.024">https://doi.org/10.1016/j.cub.2022.04.024</a>. Nicolas, W. J., Fäßler, F., Dutka, P., Schur, F. K., Jensen, G., & Meyerowitz, E. (2022). Cryo-electron tomography of the onion cell wall shows bimodally oriented cellulose fibers and reticulated homogalacturonan networks. Current Biology. Elsevier. <a href="https://doi.org/10.1016/j.cub.2022.04.024">https://doi.org/10.1016/j.cub.2022.04.024</a> Nicolas WJ, Fäßler F, Dutka P, Schur FK, Jensen G, Meyerowitz E. 2022. Cryo-electron tomography of the onion cell wall shows bimodally oriented cellulose fibers and reticulated homogalacturonan networks. Current Biology. 32(11), P2375-2389. W.J. Nicolas, F. Fäßler, P. Dutka, F.K. Schur, G. Jensen, E. Meyerowitz, Current Biology 32 (2022) P2375-2389. 113512022-05-04T06:22:06Z2025-04-15T08:25:40Z