Cytokinins (CKs) are a group of structurally related molecules derived from adenine through the substitution on the N6 atom. They act as plant hormones – a subset of plant signalling molecules regulating diverse aspects of plant growth and development such as vascular development, organogenic response, lateral root morphogenesis, and general shoot development. In addition, CKs act in response to stress and as a mobile signal for mineral availability. The proper CK signalling depends on processes which both maintain and alter CK homeostasis – the protein-mediated transport and the enzyme-catalysed conversions between the biologically active (which are able to bind to their receptors) and inactive CK forms.
Our group currently focuses on these topics:
Cytokinin degradation catalysed by cytokinin dehydrogenase (CKX) and its role in long-distance CK transport
We hypothesize that at least some CKX proteins are active in the xylem sap and directly affect CKs transported from roots to shoots. Showing so and connecting this CKX activity to a CKX form with particular substrate specificity would allow us to discuss how CK degradation shapes their long-distance flux and thus information about the nitrogen availability.
Cytokinin cell-to-cell transport and the role of equilibrative nucleoside transporters (ENTs)
CKs are transported through the vasculature, usually in the form of ribosides (nucleosides) or nucleotides. Conjugation with the ribosyl group increases the molecular polarity and bulkiness of CKs. Both prevent CKs from escaping from the vasculature by simple diffusion, suggesting the need for a transmembrane carrier. Our results suggest that certain ENTs promote the transport of CK ribosides across the plasma membrane of plant cells.
Diurnal regulation of cytokinin oscillation in Arabidopsis
The orchestration of both cytokinin and light signals is crucial for correct plant development. We investigated the impact of daily light photoperiod on the expression levels of CK-related genes and on the levels of endogenous cytokinins. We work on deciphering the molecular mechanisms underlying the diurnal oscillation of cytokinin levels.
Metabolism of cytokinin N-glucosides and the role of UGTs under stress conditions
The formation of sugar conjugates is one of the most common mechanisms leading to the deactivation of plant hormones. Glucose covalently bound to N7 and N9 atoms of cytokinin has been previously classified as an irreversible inactivation of cytokinins. We have shown that trans zeatin N9-glucoside is metabolized in Arabidopsis producing its base. We further observe CK N-glucosides oscillation during day/night photoperiod suggesting N-glucosides degradation. We focus now on CK N-glucosides de-conjugation mechanisms and the role of UGTs in N-glucosides formation during stress.
Offer to students
We welcome students interested in plant hormones and this is what we can offer:
- The course on Phytohormones (MB130P15 CZ/EN) at the Departement of Experimental Plant Biology, Faculty of Science, Charles University. Guarant: Klára Hoyerová.
- Topics for Bachelor/diploma theses at the Department of Experimental Plant Biology (Supervisor: Klára Hoyerová) and at the Department of Biochemistry (Supervisor: Klára Hoyerová, consultant: Helena Ryšlavá) at the Faculty of Science, Charles University.
- BP1: Ekvilibrativní nukleosidové transportéry – molekulární dokování fytohormonu cytokininu
- BP2: Metabolické přeměny rostlinného hormonu auxinu
- BP3: Kinetika přenosu rostlinného cytokininu přes cytoplasmatickou membránu
Methods and techniques that we use:
- In vitro cultivation of plants and plant cell cultures
- Molecular biology methods
- Phytohormone analysis in plant tissues and cells
- Cell-to-cell and long-distance transport assays of phytohormones
- Molecular docking
- Determination of CKX activity
Hošek P, Hoyerová K, Kiran NS, Dobrev PI, Zahajská L, Filepová R, Motyka V, Müller K, Kamínek M: Distinct metabolism of N‐glucosides of isopentenyladenine and trans‐zeatin determines cytokinin metabolic spectrum in Arabidopsis. New Phytologist, 2020, 225: 2423–2438. 10.1111/nph.16310
Hoyerová K, Hošek P: New insights into the metabolism and role of cytokinin N-glucosides in plants. Frontiers in Plant Science, 2020, 11:741. DOI: 10.3389/fpls.2020.00741
Pokorná E, Hluska T, Galuszka P, Hallmark HT, Dobrev PI, Záveská Drábková L, Filipi T, Holubová K, Plíhal O, Rashotte AM, Filepová R, Malbeck J, Novák O, Spíchal L, Brzobohatý B, Mazura P, Zahajská L, Motyka V: Cytokinin N-glucosides: Occurrence, metabolism and biological activities in plants. Biomolecules. 2021, 11(1):24. DOI: 10.3390/biom11010024
Nedvěd D, Hošek P, Klíma P, Hoyerová K: Differential subcellular distribution of cytokinins: How does membrane transport fit into the big picture? International Journal of Molecular Sciences. 2021, 22(7):3428. DOI: 10.3390/ijms22073428
Yang BJ, Minne M, Brunoni F, Plačková L, Petřík I, Sun Y, Nolf J, Smet W, Verstaen K, Wendrich JR, Eekhout T, Hoyerová K, Van Isterdael G, Haustraete J, Bishopp A, Farcot E, Novák O, Saeys Y, De Rybel B: Non-cell autonomous and spatiotemporal signalling from a tissue organizer orchestrates root vascular development. Nature Plants. 2021, 7:1485–1494. DOI: 10.1038/S41477-021-01017-6
Vinterhalter D, Vinterhalter B, Motyka V: Periodicity and spectral composition of light in the regulation of hypocotyl elongation of sunflower seedlings. Plants, 2022, 11, 1982. DOI: 10.3390/plants11151982
Martínková J, Klimeš A, Motyka V, Adamec L, Dobrev PI, Filepová R, Gaudinová A, Lacek J, Marešová I, Klimešová J (2023) Why is root sprouting not more common among plants? Phytohormonal clues and ecological correlates. Environmental and Experimental Botany, 205: 105147. DOI: 10.1016/j.envexpbot.2022.105147
Ćosić T, Motyka V, Raspor M, Sajid S, Devrnja N, Dobrev PI, Ninković S: Comprehensive phytohormone profiling of kohlrabi during in vitro growth and regeneration: The interplay with cytokinin and sucrose. Life, 2022, 12(10):1585. DOI: 10.3390/life12101585
El Houari I, Klíma P, Baekelandt A, Staswick PE, Uzunova V, Del Genio CI, Steenackers W, Dobrev PI, Filepová R, Novák O, Napier R, Petrášek J, Inzé D, Boerjan W, Vanholme B (2023) Non-specific effects of the CINNAMATE-4-HYDROXYLASE inhibitor piperonylic acid. Plant Journal, 115(2): 470-479. DOI: 10.1111/tpj.16237
Upadhyay RK, Motyka V, Pokorna E, Dobrev PI, Lacek J, Shao J, Lewers KS, Mattoo AK (2023) Comprehensive profiling of endogenous phytohormones and expression analysis of 1-aminocyclopropane-1-carboxylic acid synthase gene family during fruit development and ripening in octoploid strawberry (Fragaria × ananassa). Plant Physiology and Biochemistry, 196: 186-196. DOI: 10.1016/j.plaphy.2023.01.031
A new preprint on the CKX activity in xylem sap!
Happy to welcome Julie – our new technician and a great help.