Laboratory of Cell Biology
The Laboratory of Cell Biology explores selected molecular regulatory modules of plant cell polarity and morphogenesis operating mostly at the plasma membrane, at the interface of secretory pathway, membrane lipids and cytoskeleton. Plant morphogenesis is based essentially on two processes - oriented cell division and differential cell growth. As model plants we use angiosperm Arabidopsis and tobacco along with moss Physcomitrella patens. We focus on intracellular molecular mechanisms driving cellular morphogenesis such as exocytosis. Proteins participating in these mechanisms are, despite major differences in cell structure and behaviour, often very similar to those found in the fungal and animal kingdoms. The laboratory is centered around the detailed characterization and regulation of the plant vesicle tethering complex exocyst in various cell types across plant species, including plant-pathogen interactions. A significant aspect of the research is understanding of minor membrane lipids in the maintenance and establishment of cell polarity.
The Exocyst Complex in Regulation of Cell Morfogenesis and Pathogen Defence
One of elements regulating exocytosis is the exocyst, an ancient protein complex generally found in eukaryots. The exocyst serves as an effector of RAB and RHO GTPases and is crucial for polarized cell growth. It participates in targeting and tethering of secretory vesicles to secretory domains of the plasma membrane. The exocyst is consists of eight subunits termed SEC3, SEC5, SEC6, SEC8, SEC10, SEC15, EXO70, and EXO84.
We proved that the exocyst is present in plants, where it functions namely in cells characterized by intensive secretion (Hála et al 2008). Mutants of Arabidopsis thaliana in SEC8, EXO70A1, and EXO84b subunits are dwarf sterile plants (Synek et al. 2006, Fendrych et al. 2010, 2013). Other exocyst mutants are defective in seed coat formation or in polar growth of pollen tubes, root hairs and etiolated hypocotyls (Cole et al. 2005, Hála et al. 2008, Kulich et al. 2010). During cell division, the exocyst also plays an important role in establishment and maturation of the new wall separating daughter cells (Fendrych et al. 2010). Currently we also try to determine the interaction partners of the exocyst complex (e.g. RAB GTPases) and elucidate possible role of the exocyst in recycling of plasma membrane proteins.
Interestingly, we demonstrated that some isoforms of the EXO70 subunit are also involved in response to pathogen in Arabidopsis, e.g. an important role in formation of specialized structures and cell wall apposition engaged in the plant defense (Pečenková et al. 2011, 2017, Kulich et al. 2013, 2018).
Recently we employed the moss Physcomitrella patens as another model organism for this study. Using the technique of gene targeting, we are able to generate disruption mutants in exocyst subunits that exhibit significant morphological changes (Rawat et al. 2017, Brej3kov8 et al., submitted).
Small GTPases in Exocytosis
Small GTPases form a family of monomeric proteins that control many polarized processes within the plant cell. We focus on the RAB GTPase subfamily connected with membranes via double geranylgeranyl anchors. The anchors are attached by action of a protein complex called RAB geranylgeranyl transferase (RAB GGT). We study how the geranylation status affects intracellular vesicle transport, hormone signaling, and plant morphogenesis. When RAB GGT activity is decreased we observe small plants with curled leaves, loss of shoot apical dominance, no response to gravity direction changes in shoots, changes in morphogenesis in the dark (Hála et al. 2010).
RAB GTPases are currently extensively studied as important regulators of the intracellular vesicular transport. Using biochemical, molecular biological and genetic approaches, we study RAB GTPases involved in terminal steps of exocytosis – especially those regulating the exocyst complex. We attempt to identify interactors of such RABs as a tool to determine particular role of different RABs in the plant cell.
Furthermore, we study RAB GDP dissociation inhibitors (RAB GDI) that belong to basic regulators of small GTPases with redundant functions and play essential role in the plant cell.
Signaling Lipids in the Regulation of Plant PolarityMembrane phosphoinositides and phosphatidic acid, along with lipases, kinases and phosphatases, are known controllers of cell polarity and vesicular trafficking in yeast and animal cells. Phospholipids function in eukaryotic cells both as classical "second messengers" and as localization cues, enabling the recruitment of phospholipid-binding proteins to specific membranes or membrane domains. We use a growing pollen tube model to address the relationship of these two aspects of membrane lipid function, especially as related to substrates and products of phospholipase D in plant cell polarization (Potocký et al. 2014). We described the reciprocal character of regulation of phospholipase D activity and actin dynamics restricted to PIP2-dependent PLDβ, and suggest that this PLD–actin interaction is important for general tip growth of plant cells (Pleskot et al. 2010).
We are currently studying the involvement of other PLD isoforms in pollen tube growth and trying to describe the complex dynamics of various signaling lipids during the establishment and maintenance of polar cell expansion (Platre et al. 2018).
Multiscale analysis of membrane-protein interfacesTo describe the role of protein–lipid interplay in cell polarity, it is important to understand the mechanistic details of lipid-lipid-protein, and protein–protein interactions. Molecular dynamics (MD) simulations have been shown to play an invaluable role in the description of dynamic interaction of membrane proteins with phospholipids, which could be hardly obtained by experimental approaches. In the past 5 years we have made significant contribution in establishing MD-based research in plant science community, focusing mostly on the interaction of exocyst and cytoskeleton-regulating proteins with membranes (Pleskot et al. 2012, 2015).
head of the laboratorysenior scientist
- Ing. Martin Potocký Ph.D.
- RNDr. Viktor Žárský CSc.
- Mgr. Peter Sabol PhD.
- Bc. Jana Šťovíčková
Number of grants/projects: 14
- Good-Cop/Bad-Cop: Distinct roles of anionic phospholipids in plant endocytosis , GA ČR , Martin Potocký
- SIGNALS - The role of anionic phospholipids in the regulation of endocytosis in tip-growing plant cells , MŠMT , Martin Potocký
- Control of plant exocyst function by protein phosphorylation in root hairs and pollen tubes - role of unconventional exocyst complex subunits EXO70C , GA ČR , Viktor Žárský
- Multifaceted analysis of diacylglycerol kinase family in plants , GA ČR , Přemysl Pejchar
- Plant exocyst complex function in autophagy-related membrane transport , GA ČR , Tamara Pečenková
- Multiscale analysis of signalling phospholipids and their interaction protein partners in the regulation of plant tip growth , GA ČR , Martin Potocký
- Funkce rostlinného poutacího komplexu exocyst v exocytóze, buněčném dělení a biogenezi buněčné stěny , GA ČR , Michal Hála
- Úloha diacylglycerolu při toxickém působení hliníku u rostlin , GA ČR , Přemysl Pejchar
- Exocyst, poutací komplex sekretorických váčků, v polarizaci transportu auxinu , GA ČR , Lukáš Synek
- Charakterizace vybraných příslušníků nových skupin rostlinných forminů - třídy II a třídy III. , GA ČR , Viktor Žárský
- The role of the exocyst complex in the plant-pathogen interaction , GA ČR , Tamara Pečenková
- Chracterisation of NADPH oxidase from tobacco pollen and its role in regulation of polar cell expansion , GA ČR , Martin Potocký
- Phosphatidic acid and diacylglycerol-mediated signalling in the polar growth of plant cells , GA AV , Martin Potocký
- Transkriptom mutanta exo70A1 a buněčné funkce EXO70A1, podjednotky komplexu exocyst, u Arabidopsis thaliana , GA AV , Lukáš Synek
Number of publications: 115
- PLANT JOURNAL 103 212-226 2020 (External fulltext)
Redundant and diversified roles among selected Arabidopsis thaliana EXO70 paralogs during biotic stress responsesFRONTIERS IN PLANT SCIENCE 11 960 2020 (External fulltext)
- PLANT PHYSIOLOGY 2020
Phospholipase Dα1 mediates the high-Mg2+ stress response partially through regulation of K+ homeostasisPLANT CELL AND ENVIRONMENT 2020
Three subfamilies of exocyst EXO70 family subunits in land plants: early divergence and ongoing functional specializationJOURNAL OF EXPERIMENTAL BOTANY 71 49-62 2020 (External fulltext)
Synergy among exocyst and SNARE interactions identifies a functional hierarchy in secretion during vegetative growthPLANT CELL in press https://doi.org/10.1105/tpc.20.00280 2020 (External fulltext)
Division of labor between two actin nucleators-the formin FH1 and the ARP2/3 complex-in arabidopsis epidermal cell morphogenesisFRONTIERS IN PLANT SCIENCE 11 148 2020 (External fulltext)
- JOURNAL OF EXPERIMENTAL BOTANY 2020