Dokument: Identifying new components in plasmodesmal gating
| Titel: | Identifying new components in plasmodesmal gating | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=70060 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20260806-091452-4 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | Ejike, Jona Obinna [Autor] | |||||||
| Dateien: |
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| Beitragende: | Prof. Dr. Frommer, Wolf B. [Gutachter] Prof. Dr. Rüdiger Simon [Gutachter] | |||||||
| Stichwörter: | plasmodesmata, transport | |||||||
| Dewey Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik » 570 Biowissenschaften; Biologie | |||||||
| Beschreibung: | Intercellular communication is an ancient evolutionary trait and a prerequisite for
multicellularity. Most multicellular species evolved intercellular connections that enable and control molecular exchange. Filamentous cyanobacteria harbor septal junctions, animals gap junctions, and fungi septal pores. The green lineage, including green algae and terrestrial plants, evolved plasmodesmata (PD). Plasma membrane (PM)-lined nanometer-sized channels that traverse the cell wall and create a cytoplasmic continuum of inter-connected cells (symplasm). PD also connect the endoplasmic reticulum (ER) of adjacent cells by a constricted ER tubule, termed the desmotubule. The PD’s cytoplasmic sleeve between PM and desmotubule membrane is described as the main passageway for intercellular exchange. PD exchange small species like ions, metabolites, plant hormones and peptides, as well as macromolecules like proteins and RNAs, and hence are essential for coordinated plant growth, development, and immunity. Despite their prerequisite for plant multicellularity, the composition structure and transport mechanism of PD remain elusive. In this thesis, I aimed to identify novel components that contribute to PD-mediated intercellular transport. Therefore, firstly, I contributed to the generation of a high-confidence PD-proteome of the basal terrestrial plant Physcomitrium patens. This allowed to identify evolutionary conserved PD protein families by an iterative combination of PD protein enrichment, feature scoring, and systematic-large-scale localization in planta. In particular, cell wall residual protein families could be robustly separated in PD- and non-PD localized phylogenetic clades. Cell wall modifications have long been described to regulate the PD aperture. Specifically, callose turnover at PD neck regions has been widely accepted as one of the regulators of the plasmodesmal transport mechanism. Where callose accumulations constrict, and callose depletion dilates the PD aperture. Notably, many transport phenomena across PD cannot be described by the size of the PD aperture alone. As PD are cytoplasmic bridges, I set out to challenge the common model and asked if there might be cytoplasmic components that control PD passage. Inspired by the nuclear pore complex (NPC), a nanometer-sized pore with similar transport properties, I hypothesized that PD might harbor a similar permeability barrier. NPCs control nucleocytoplasmic transport, forming conduits that connect transcription and translation. The permeability barrier in NPCs is a phase-separation domain formed by phenylalanine-glycine-rich nucleoporins (FG-NUP). Nucleocytoplasmic cargo transport can be facilitated by FG-interacting nuclear transport receptors (NTRs). Surprisingly, NUPs found in our P. patens PD proteome, localized to PD in planta. Further analysis of Arabidopsis thaliana NUPs validated the dual-localization of 7 NUPs to NPC and PD. Mutants of the plant-specific transmembrane NUP CPR5 showed callose-independent reduction of macromolecular cell-cell transport. These results indicated the functional role of NUPs in intercellular transport. To further test NUP involvement at PD, I generated an extensive list of P. patens nup knock-out mutants and NUP-fluorescent protein (FP) knock-in lines via CRISPR-Cas9 and prime editing. Finally, I provide evidence that, like in the NPC, PD passage is not only dependent on the cargo’s mass and dimensions but also facilitated by NTR-like surface properties. This is demonstrated by the intercellular mobility of an engineered tetrameric NTR-like GFP, compared to a non-mobile 3xmCherry tandem of similar diameter and reduced mass. Conversely, only the movement of the tetrameric NTR-like GFP is reduced in a fg-nup98a/b mutant that contain less than 50% of the wild-type encoded FG content. While a 2xEGFP tandem moves similarly in WT and fg-nup98a/b mutant. In summary, this thesis proposes a novel PD transport mechanism in which NUPs were recruited to form a PD pore gating complex (PDPC), which enacts an FG-based phase separation that controls intercellular permeability. Simultaneously enabling facilitated passage of NTR-like cargo and exclusion of non-specific molecules. | |||||||
| Lizenz: |  Dieses Werk ist lizenziert unter einer Creative Commons Namensnennung 4.0 International Lizenz | |||||||
| Fachbereich / Einrichtung: | Mathematisch- Naturwissenschaftliche Fakultät » WE Biologie | |||||||
| Dokument erstellt am: | 06.08.2026 | |||||||
| Dateien geändert am: | 06.08.2026 | |||||||
| Promotionsantrag am: | 26.09.2023 | |||||||
| Datum der Promotion: | 09.05.2025 |
