TPX2 (Targeting Protein for Xklp2) is an evolutionary conserved microtubule-associated protein important for microtubule nucleation and mitotic spindle assembly. The protein was described as an activator of the mitotic kinase Aurora A in humans and the Arabidopsis AURORA1 (AUR1) kinase. In contrast to animal genomes that encode only one TPX2 gene, higher plant genomes encode a family with several TPX2-LIKE gene members (TPXL). TPXL genes of Arabidopsis can be divided into two groups. Group A proteins (TPXL2, 3, 4, and 8) contain Aurora binding and TPX2_importin domains, while group B proteins (TPXL1, 5, 6, and 7) harbor an Xklp2 domain. Canonical TPX2 contains all the above-mentioned domains. We confirmed using in vitro kinase assays that the group A proteins contain a functional Aurora kinase binding domain. Transient expression of Arabidopsis TPX2-like proteins in Nicotiana benthamiana revealed preferential localization to microtubules and nuclei. Co-expression of AUR1 together with TPX2-like proteins changed the localization of AUR1, indicating that these proteins serve as targeting factors for Aurora kinases. Taken together, we visualize the various localizations of the TPX2-LIKE family in Arabidopsis as a proxy to their functional divergence and provide evidence of their role in the targeted regulation of AUR1 kinase activity.
- MeSH
- Arabidopsis cytologie genetika metabolismus MeSH
- kinasy aurora metabolismus MeSH
- mikrotubuly metabolismus MeSH
- proteinové domény MeSH
- proteiny asociované s mikrotubuly analýza genetika metabolismus MeSH
- proteiny huseníčku analýza genetika metabolismus MeSH
- rostlinné geny MeSH
- sekvence aminokyselin MeSH
- vazba proteinů MeSH
- Publikační typ
- časopisecké články MeSH
The Arabidopsis EH proteins (AtEH1/Pan1 and AtEH2/Pan1) are components of the endocytic TPLATE complex (TPC) which is essential for endocytosis. Both proteins are homologues of the yeast ARP2/3 complex activator, Pan1p. Here, we show that these proteins are also involved in actin cytoskeleton regulated autophagy. Both AtEH/Pan1 proteins localise to the plasma membrane and autophagosomes. Upon induction of autophagy, AtEH/Pan1 proteins recruit TPC and AP-2 subunits, clathrin, actin and ARP2/3 proteins to autophagosomes. Increased expression of AtEH/Pan1 proteins boosts autophagosome formation, suggesting independent and redundant pathways for actin-mediated autophagy in plants. Moreover, AtEHs/Pan1-regulated autophagosomes associate with ER-PM contact sites (EPCS) where AtEH1/Pan1 interacts with VAP27-1. Knock-down expression of either AtEH1/Pan1 or VAP27-1 makes plants more susceptible to nutrient depleted conditions, indicating that the autophagy pathway is perturbed. In conclusion, we identify the existence of an autophagy-dependent pathway in plants to degrade endocytic components, starting at the EPCS through the interaction among AtEH/Pan1, actin cytoskeleton and the EPCS resident protein VAP27-1.
- MeSH
- aktiny metabolismus MeSH
- Arabidopsis metabolismus ultrastruktura MeSH
- autofagie MeSH
- autofagozomy metabolismus ultrastruktura MeSH
- biologické modely MeSH
- buněčná membrána metabolismus ultrastruktura MeSH
- endocytóza * MeSH
- endoplazmatické retikulum metabolismus ultrastruktura MeSH
- fylogeneze MeSH
- komplex proteinů 2-3 souvisejících s aktinem metabolismus MeSH
- mikrofilamenta metabolismus MeSH
- mikrofilamentové proteiny metabolismus MeSH
- proteiny huseníčku metabolismus MeSH
- Saccharomyces cerevisiae - proteiny metabolismus MeSH
- vazba proteinů MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Aurora kinases are key regulators of mitosis. Multicellular eukaryotes generally possess two functionally diverged types of Aurora kinases. In plants, including Arabidopsis (Arabidopsis thaliana), these are termed α- and β-Auroras. As the functional specification of Aurora kinases is determined by their specific interaction partners, we initiated interactomics analyses using both Arabidopsis α-Aurora kinases (AUR1 and AUR2). Proteomics results revealed that TPX2-LIKE PROTEINS2 and 3 (TPXL2/3) prominently associated with α-Auroras, as did the conserved TPX2 to a lower degree. Like TPX2, TPXL2 and TPXL3 strongly activated the AUR1 kinase but exhibited cell-cycle-dependent localization differences on microtubule arrays. The separate functions of TPX2 and TPXL2/3 were also suggested by their different influences on AUR1 localization upon ectopic expressions. Furthermore, genetic analyses showed that TPXL3, but not TPX2 and TPXL2, acts nonredundantly to enable proper embryo development. In contrast to vertebrates, plants have an expanded TPX2 family and these family members have both redundant and unique functions. Moreover, as neither TPXL2 nor TPXL3 contains the C-terminal Kinesin-5 binding domain present in the canonical TPX2, the targeting and activity of this kinesin must be organized differently in plants.
- MeSH
- aktivace enzymů genetika MeSH
- Arabidopsis embryologie genetika metabolismus MeSH
- geneticky modifikované rostliny MeSH
- konfokální mikroskopie MeSH
- protein-serin-threoninkinasy genetika metabolismus MeSH
- proteiny asociované s mikrotubuly genetika metabolismus MeSH
- proteiny buněčného cyklu genetika metabolismus MeSH
- proteiny huseníčku genetika metabolismus MeSH
- proteomika metody MeSH
- regulace genové exprese u rostlin MeSH
- sekvence aminokyselin MeSH
- sekvenční homologie aminokyselin MeSH
- semena rostlinná embryologie genetika metabolismus MeSH
- vazba proteinů MeSH
- vývojová regulace genové exprese MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, U.S. Gov't, Non-P.H.S. MeSH
Trafficking of proteins and lipids within the plant endomembrane system is essential to support cellular functions and is subject to rigorous regulation. Despite this seemingly strict regulation, endomembrane trafficking needs to be dynamically adjusted to ever-changing internal and environmental stimuli, while maintaining cellular integrity. Although often overlooked, the versatile second messenger Ca2+is intimately connected to several endomembrane-associated processes. Here, we discuss the impact of electrostatic interactions between Ca2+and anionic phospholipids on endomembrane trafficking, and illustrate the direct role of Ca2+sensing proteins in regulating endomembrane trafficking and membrane integrity preservation. Moreover, we discuss how Ca2+can control protein sorting within the plant endomembrane system. We thus highlight Ca2+signaling as a versatile mechanism by which numerous signals are integrated into plant endomembrane trafficking dynamics.
Plant cytokinesis is orchestrated by a specialized structure, the phragmoplast. The phragmoplast first occurred in representatives of Charophyte algae and then became the main division apparatus in land plants. Major cellular activities, including cytoskeletal dynamics, vesicle trafficking, membrane assembly, and cell wall biosynthesis, cooperate in the phragmoplast under the guidance of a complex signaling network. Furthermore, the phragmoplast combines plant-specific features with the conserved cytokinetic processes of animals, fungi, and protists. As such, the phragmoplast represents a useful system for understanding both plant cell dynamics and the evolution of cytokinesis. We recognize that future research and knowledge transfer into other fields would benefit from standardized terminology. Here, we propose such a lexicon of terminology for specific structures and processes associated with plant cytokinesis.
- MeSH
- biologické modely MeSH
- buněčná membrána metabolismus MeSH
- buněčné dělení MeSH
- chromozomy rostlin metabolismus MeSH
- cytokineze * MeSH
- cytoplazma metabolismus MeSH
- cytoskelet metabolismus MeSH
- mikrotubuly metabolismus MeSH
- rostlinné buňky metabolismus MeSH
- terminologie jako téma * MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy MeSH
- Research Support, U.S. Gov't, Non-P.H.S. MeSH
