TPX2 performs multiple roles in microtubule organization. Previously, it was shown that plant AtTPX2 binds AtAurora1 kinase and colocalizes with microtubules in a cell cycle-specific manner. To elucidate the function of TPX2 further, this work analysed Arabidopsis cells overexpressing AtTPX2-GFP. Distinct arrays of bundled microtubules, decorated with AtTPX2-GFP, were formed in the vicinity of the nuclear envelope and in the nuclei of overexpressing cells. The microtubular arrays showed reduced sensitivity to anti-microtubular drugs. TPX2-mediated formation of nuclear/perinuclear microtubular arrays was not specific for the transition to mitosis and occurred independently of Aurora kinase. The fibres were not observed in cells with detectable programmed cell death and, in this respect, they differed from TPX2-dependent microtubular assemblies functioning in mammalian apoptosis. Colocalization and co-purification data confirmed the interaction of importin with AtTPX2-GFP. In cells with nuclear foci of overexpressed AtTPX2-GFP, strong nuclear signals for Ran and importin diminished when microtubular arrays were assembled. This observation suggests that TPX2-mediated microtubule formation might be triggered by a Ran cycle. Collectively, the data suggest that in the acentrosomal plant cell, in conjunction with importin, overexpressed AtTPX2 reinforces microtubule formation in the vicinity of chromatin and the nuclear envelope.

• Klíčová slova
• Arabidopsis thaliana, AtTPX2, Aurora kinase, Ran., fibres, importin, microtubules, nuclei, γ-tubulin,
• MeSH
• apoptóza MeSH
• Arabidopsis cytologie   enzymologie   metabolismus   MeSH
• buněčné jádro metabolismus   MeSH
• centrozom metabolismus   MeSH
• chromatin metabolismus   MeSH
• jaderný obal metabolismus   MeSH
• karyoferiny metabolismus   MeSH
• kinasy Aurora metabolismus   MeSH
• mikrotubuly metabolismus   MeSH
• mitóza MeSH
• počítačová simulace MeSH
• proteiny asociované s mikrotubuly metabolismus   MeSH
• proteiny huseníčku metabolismus   MeSH
• rostlinné buňky metabolismus   MeSH
• subcelulární frakce metabolismus   MeSH
• transport proteinů MeSH
• tubulin metabolismus   MeSH
• zelené fluorescenční proteiny metabolismus   MeSH
• zobrazování trojrozměrné MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• chromatin MeSH
• karyoferiny MeSH
• kinasy Aurora MeSH
• proteiny asociované s mikrotubuly MeSH
• proteiny huseníčku MeSH
• TPX2 protein, Arabidopsis MeSH Prohlížeč
• tubulin MeSH
• zelené fluorescenční proteiny MeSH

• The conserved family of Aurora kinases has multiple functions during mitosis. The roles of plant Aurora kinases have been characterized using inhibitor treatments. • We down-regulated Aurora kinases in Arabidopsis thaliana using RNA interference (RNAi). We carried out a detailed phenotypic analysis of Aurora RNAi plants, biochemical and microscopic studies of AtAurora1 kinase together with AtTPX2 (targeting protein for Xklp2) and γ-tubulin. • Cell division defects were observed in plants with reduced expression of Aurora kinases. Furthermore, the maintenance of primary meristems was compromised and RNAi seedlings entered endoreduplication prematurely. AtAurora1, its activator AtTPX2, and γ-tubulin were associated with microtubules in vitro; they were attached to regrowing kinetochore microtubules and colocalized on spindle microtubules and with a subset of early phragmoplast microtubules. Only the AtAurora1 kinase was translocated to the area of the cell plate. • RNAi silencing of Aurora kinases showed that, in addition to their function in regulating mitosis, the kinases are required for maintaining meristematic activity and controlling the switch from meristematic cell proliferation to differentiation and endoreduplication. The colocalization and co-fractionation of AtAurora1 with AtTPX2, and γ-tubulin on microtubules in a cell cycle-specific manner suggests that AtAurora1 kinase may function to phosphorylate substrates that are critical to the spatiotemporal regulation of acentrosomal microtubule formation and organization.

• MeSH
• Arabidopsis enzymologie   genetika   MeSH
• buněčné dělení MeSH
• down regulace MeSH
• duplikace genu genetika   MeSH
• fenotyp MeSH
• kinasy Aurora MeSH
• meristém enzymologie   genetika   růst a vývoj   MeSH
• mikrotubuly metabolismus   MeSH
• protein-serin-threoninkinasy metabolismus   MeSH
• proteiny asociované s mikrotubuly metabolismus   MeSH
• proteiny huseníčku metabolismus   MeSH
• RNA interference MeSH
• transport proteinů MeSH
• tubulin metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• AUR1 protein, Arabidopsis MeSH Prohlížeč
• kinasy Aurora MeSH
• protein-serin-threoninkinasy MeSH
• proteiny asociované s mikrotubuly MeSH
• proteiny huseníčku MeSH
• TPX2 protein, Arabidopsis MeSH Prohlížeč
• tubulin MeSH