A better understanding of phytohormone physiology can provide an essential basis to coherently achieve a conservation drive/strategy for valuable plant species. We evaluated the distribution pattern of cytokinins (CKs) and phenolic compounds in different organs of 1-year-old greenhouse-grown Tulbaghia simmleri pre-treated (during micropropagation) with three aromatic CKs (benzyladenine = BA, meta-topolin = mT, meta-topolin riboside = mTR). The test species is highly valuable due to its medicinal and ornamental uses. Based on UHPLC-MS/MS quantification, mT and mTR pre-treated plants had the highest total CK, mostly resulting from the isoprenoid CK-type, which occurred at highest concentrations in the roots. Although occurring in much lower concentrations when compared to isoprenoid CKs, aromatic CKs were several-fold more abundant in the root of mT pre-treated plants than with other treatments. Possibly related to the enhanced aromatic CKs, free bases and ribonucleotides, plants pre-treated with mT generally displayed better morphology than the other treatments. A total of 12 bioactive phenolic compounds, including four hydroxybenzoic acids, five hydroxycinnamic acids and three flavonoids at varying concentrations, were quantified in T. simmleri. The occurrence, distribution and levels of these phenolic compounds were strongly influenced by the CK pre-treatments, thereby confirming the importance of CKs in phenolic biosynthesis pathways.

• Klíčová slova
• Acclimatisation, UHPLC, conservation, meta-topolins, phytochemicals, plant growth regulators, wild garlic,
• MeSH
• cytokininy metabolismus   farmakologie   MeSH
• fenoly metabolismus   MeSH
• flavonoidy metabolismus   MeSH
• hydroxybenzoáty metabolismus   MeSH
• kořeny rostlin účinky léků   metabolismus   MeSH
• kyseliny kumarové metabolismus   MeSH
• liliovité účinky léků   metabolismus   MeSH
• regulátory růstu rostlin metabolismus   farmakologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• cytokininy MeSH
• fenoly MeSH
• flavonoidy MeSH
• hydroxybenzoáty MeSH
• kyseliny kumarové MeSH
• regulátory růstu rostlin MeSH

A number of scientific reports published to date contain data on endogenous levels of various phytohormones in potato (Solanum tuberosum L.) but a complete cytokinin profile of potato tissues, that would include data on all particular molecular forms of cytokinin, has still been missing. In this work, endogenous levels of all analytically detectable isoprenoid cytokinins, as well as the auxin indole-3-acetic acid (IAA), and abscisic acid (ABA) have been determined in shoots and roots of 30 day old in vitro grown potato (cv. Désirée). The results presented here are generally similar to other data reported for in vitro grown potato plants, whereas greenhouse-grown plants typically contain lower levels of ABA, possibly indicating that in vitro grown potato is exposed to chronic stress. Cytokinin N-glucosides, particularly N7-glucosides, are the dominant cytokinin forms in both shoots and roots of potato, whereas nucleobases, as the bioactive forms of cytokinins, comprise a low proportion of cytokinin levels in tissues of potato. Differences in phytohormone composition between shoots and roots of potato suggest specific patterns of transport and/or differences in tissue-specific metabolism of plant hormones. These results represent a contribution to understanding the hormonomics of potato, a crop species of extraordinary economic importance.

• MeSH
• cytokininy analýza   metabolismus   MeSH
• fyziologický stres MeSH
• kořeny rostlin metabolismus   MeSH
• kyselina abscisová analýza   metabolismus   MeSH
• kyseliny indoloctové analýza   metabolismus   MeSH
• regulátory růstu rostlin analýza   metabolismus   MeSH
• Solanum tuberosum růst a vývoj   metabolismus   MeSH
• tandemová hmotnostní spektrometrie MeSH
• výhonky rostlin metabolismus   MeSH
• vysokoúčinná kapalinová chromatografie MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• cytokininy MeSH
• indoleacetic acid MeSH Prohlížeč
• kyselina abscisová MeSH
• kyseliny indoloctové MeSH
• regulátory růstu rostlin MeSH

Recent advances in cytokinin analysis have made it possible to measure the content of 22 cytokinin metabolites in the tissue of developing tobacco seedlings. Individual types of cytokinins in plants are interconverted to their respective forms by several enzymatic activities (5'-AMP-isopentenyltransferase, adenosine nucleosidase, 5'-nucleotidase, adenosine phosphorylase, adenosine kinase, trans-hydroxylase, zeatin reductase, beta-glucosidase, O-glucosyl transferase, N-glucosyl transferase, cytokinin oxidase). This paper reports modelling and measuring of the dynamics of endogenous cytokinins in tobacco plants grown on media supplemented with isopentenyl adenine (IP), zeatin (Z) and dihydrozeatin riboside (DHZR). Differences in phenotypes generated by the three cytokinins are shown and discussed, and the assumption that substrate concentration drives enzyme kinetics underpinned the construction of a simple mathematical model of cytokinin metabolism in developing seedlings. The model was tested on data obtained from liquid chromatography/tandem mass spectrometry cytokinin measurements on tobacco seedlings grown on Murashige and Skoog agar nutrient medium, and on plants grown in the presence of IP, Z and DHZR. A close match was found between measured and simulated data, especially after a series of iterative parameter searches, in which the parameters were set to obtain the best fit with one of the data sets.

• MeSH
• adenin analogy a deriváty   farmakologie   MeSH
• biologické modely MeSH
• cytokininy analýza   metabolismus   MeSH
• fenotyp MeSH
• metoda Monte Carlo MeSH
• semenáček účinky léků   růst a vývoj   metabolismus   MeSH
• tabák účinky léků   růst a vývoj   metabolismus   MeSH
• zeatin analogy a deriváty   farmakologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• adenin MeSH
• cytokininy MeSH
• zeatin MeSH

Cytokinins modulate a number of important developmental processes, including the last phase of leaf development, known as senescence, which is associated with chlorophyll breakdown, photosynthetic apparatus disintegration and oxidative damage. There is ample evidence that cytokinins can slow down all these senescence-accompanying changes. Here, we review relationships between the various mechanisms of action of these regulatory molecules. We highlight their connection to photosynthesis, the pivotal process that generates assimilates, however may also lead to oxidative damage. Thus, we also focus on cytokinin induction of protective responses against oxidative damage. Activation of antioxidative enzymes in senescing tissues is described as well as changes in the levels of naturally occurring antioxidative compounds, such as phenolic acids and flavonoids, in plant explants. The main goal of this review is to show how the biological activities of cytokinins may be related to their chemical structure. New links between molecular aspects of natural cytokinins and their synthetic derivatives with antisenescent properties are described. Structural motifs in cytokinin molecules that may explain why these molecules play such a significant regulatory role are outlined.

• Klíčová slova
• antioxidant, antioxidant enzymes, antisenescent, cytokinin, derivative, genes, photosynthesis, plant defence, structure and activity relationship,
• MeSH
• antioxidancia chemie   metabolismus   MeSH
• cytokininy chemie   metabolismus   MeSH
• flavonoidy analýza   MeSH
• fotosyntéza MeSH
• listy rostlin chemie   růst a vývoj   fyziologie   MeSH
• molekulární struktura MeSH
• rostliny chemie   MeSH
• vývoj rostlin MeSH
• vztahy mezi strukturou a aktivitou MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• antioxidancia MeSH
• cytokininy MeSH
• flavonoidy MeSH

The prolongation of the effect of exogenous cytokinins by inhibition of their inactivation was studied in Raphanus sativus L. cv. Rampouch. As in radish the main way of cytokinin inactivation is their N-glucosylation, inhibitors of this pathway, papaverine, theophylline and olomoucine, as well as two olomoucine analogues, bohemine and roscovitine, were tested. The latter ones, which function as potent inhibitors of cyclin-dependent kinases, have also been found to effectively inhibit cytokinin N-glucosylation. Incubation (24 h) of de-rooted radish seedlings with inhibitors resulted in c. 50% decrease of the conversion of model cytokinins, [(3)H]dihydrozeatin and [(3)H]N(6)-benzyladenine, to the corresponding 7N-glucosides. Simultaneously the level of the non-metabolized cytokinin bases was elevated. The activity of cytokinin oxidase/dehydrogenase (EC 1.5.99.12) was suppressed in a dose dependent manner. The concentration of physiologically active endogenous cytokinins was not increased significantly by inhibitor application. The inhibition of N-glucosylation was in the case of olomoucine, bohemine and roscovitine accompanied by the accumulation of physiologically nonactive cis-zeatin derivatives. The impact of inhibitors on the endogenous cytokinin pool seems to be balanced by the mechanisms involved in the maintenance of cytokinin homeostasis.

• Publikační typ
• časopisecké články MeSH

The dynamics of individual endogenous cytokinins within the growth cycle (subculture interval) of an auxin-dependent and cytokinin-independent cell suspension culture ofNicotiana tabacum L. (strain VBI-0) were determined using high performance liquid chromatography and radioimmunoassay. In cells grown at an optimum auxin concentration the transient maxima of N(6)-(Δ(2)-isopentenyl)adenine and N(6)-(Δ(2)-isopentenyl)-adenosine correlated with the onset of cell division. Cultivation of the cells in a partially auxin-deprived medium resulted in ca. tenfold increase of all endogenous cytokinins. A very distinct maximum of N(6)-(Δ(2)-sopentenyl) adenine appeared at the beginning of subculture. This indicates that a lack of auxin induced an accumulation of cytokinins predominantly in the form of the free bases, which are physiologically more active than the corresponding ribosides.

• Publikační typ
• časopisecké články MeSH

The effect of 10 µM meta-topolin (mT) and meta-topolin riboside (mTR) on in vitro proliferation and anomalies of Pistacia vera L. were evaluated and compared to that of 6-benzylaminopurine (BA). The highest proliferation rate (15.6) was recorded in the mT-medium, with a value 6 times higher than in BA-medium. Moreover, the lowest percentage of hyperhydric usable shoots (58,9%) and callus weight (46,9%) were found in mTR-treated shoots. Shoot tip as well as leaf necrosis were not influenced by cytokinin (CK) type. Image analysis was used to evaluate photosynthetic efficiency as well as anthocyanin index. Photosynthesis was more efficient with BA and mTR but the higher anthocyanin accumulation in BA-treated shoots suggests more stress. Endogenous CKs and their metabolites were determined in seedlings and, for the first time, the metabolism of exogenous BA, mT and mTR was studied in pistachio. The stimulating effect on cis-zeatin and its riboside and the appearance of BA and traces of ortho-topolin and para-topolin as natural CKs are discussed. The quantitative and qualitative CK metabolite analyses provides some initial clues as to why topolin would be superior to BA in terms of proliferation rate and avoiding hyperhydricity and allowed a better understanding of the effect of exogenous administration of CK.

• Klíčová slova
• Endogenous cytokinin, Pistachio, Shoot tip necrosis, meta-topolin riboside,
• MeSH
• anthokyaniny MeSH
• cytokininy * metabolismus   MeSH
• Pistacia * metabolismus   MeSH
• proliferace buněk MeSH
• semenáček metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• anthokyaniny MeSH
• cytokininy * MeSH

Redirection of intercellular auxin fluxes via relocalization of the PIN-FORMED 3 (PIN3) and PIN7 auxin efflux carriers has been suggested to be necessary for the root gravitropic response. Cytokinins have also been proposed to play a role in controlling root gravitropism, but conclusive evidence is lacking. We present a detailed study of the dynamics of root bending early after gravistimulation, which revealed a delayed gravitropic response in transgenic lines with depleted endogenous cytokinins (Pro35S:AtCKX) and cytokinin signaling mutants. Pro35S:AtCKX lines, as well as a cytokinin receptor mutant ahk3, showed aberrations in the auxin response distribution in columella cells consistent with defects in the auxin transport machinery. Using in vivo real-time imaging of PIN3-GFP and PIN7-GFP in AtCKX3 overexpression and ahk3 backgrounds, we observed wild-type-like relocalization of PIN proteins in the columella early after gravistimulation, with gravity-induced relocalization of PIN7 faster than that of PIN3. Nonetheless, the cellular distribution of PIN3 and PIN7 and expression of PIN7 and the auxin influx carrier AUX1 was affected in AtCKX overexpression lines. Based on the retained cytokinin sensitivity in pin3 pin4 pin7 mutant, we propose the AUX1-mediated auxin transport rather than columella-located PIN proteins as a target of endogenous cytokinins in the control of root gravitropism.

• Klíčová slova
• AUX1, Arabidopsis, PIN-FORMED (PIN), auxin, cytokinins, root gravitropism,
• MeSH
• Arabidopsis účinky léků   fyziologie   MeSH
• biologické modely MeSH
• biologický transport účinky léků   MeSH
• cytokininy farmakologie   MeSH
• gravitace MeSH
• gravitropismus účinky léků   MeSH
• kořeny rostlin účinky léků   fyziologie   MeSH
• kyseliny indoloctové metabolismus   MeSH
• meristém účinky léků   fyziologie   MeSH
• proteiny huseníčku metabolismus   MeSH
• signální transdukce účinky léků   MeSH
• zelené fluorescenční proteiny metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• AUX1 protein, Arabidopsis MeSH Prohlížeč
• cytokininy MeSH
• kyseliny indoloctové MeSH
• proteiny huseníčku MeSH
• zelené fluorescenční proteiny MeSH

The putative role of cytokinins in processes leading to reproductive development of plants was investigated by analysing the shoot apical parts of a winter cultivar of oilseed rape (Brassica napus L. var. oleifera, cv. Górczański). The endogenous cytokinin levels were measured by liquid chromatography-tandem mass spectrometry (LC-MS) in the shoot apices of vegetative plants (grown at 20/17°C with a 16/8h day/night regime) and vernalized plants (56 days at 5/2°C with a 16/8h photoperiod) at different times during floral transition. During vernalization, the content of all isoprenoid cytokinins increased significantly, coinciding well with the onset of the early stages of reproductive development. Cytokinin levels reached their maxima when most of the plants became irreversibly reproductive (after 42 days of cold treatment). cis-Zeatin riboside (unequivocally identified by quadrupole-time-of-flight MS) accounted for ca. 87-89% of the total isoprenoid cytokinin content in control and vernalized plants, whilst N(6)-isopentenyladenosine ( approximately 6% in control and approximately 8% in vernalized plants) and cis-zeatin (approxiamtely 2% in control and approximately 1% in vernalized plants) were the next most abundant cytokinins. In the post-vernalization period, endogenous cytokinin levels decreased, but remained significantly higher in the reproductive plants than in the vegetative controls. These results suggest that cytokinins, especially those of the cis-zeatin type, are involved in vernalization-induced reproductive development of B. napus.

• MeSH
• Brassica napus klasifikace   růst a vývoj   metabolismus   MeSH
• chromatografie kapalinová MeSH
• cytokininy metabolismus   MeSH
• druhová specificita MeSH
• isopentenyladenosin analogy a deriváty   metabolismus   MeSH
• květy růst a vývoj   metabolismus   MeSH
• meristém metabolismus   MeSH
• nízká teplota * MeSH
• roční období MeSH
• rozmnožování fyziologie   MeSH
• tandemová hmotnostní spektrometrie MeSH
• zeatin metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• cytokininy MeSH
• isopentenyladenosin MeSH
• zeatin MeSH

Light and cytokinins are known to be the key players in the regulation of plant senescence. In detached leaves, the retarding effect of light on senescence is well described; however, it is not clear to what extent is this effect connected with changes in endogenous cytokinin levels. We have performed a detailed analysis of changes in endogenous content of 29 cytokinin forms in detached leaves of Arabidopsis thaliana (wild-type and 3 cytokinin receptor double mutants). Leaves were kept under different light conditions, and changes in cytokinin content were correlated with changes in chlorophyll content, efficiency of photosystem II photochemistry, and lipid peroxidation. In leaves kept in darkness, we have observed decreased content of the most abundant cytokinin free bases and ribosides, but the content of cis-zeatin increased, which indicates the role of this cytokinin in the maintenance of basal leaf viability. Our findings underscore the importance of light conditions on the content of specific cytokinins, especially N6 -(Δ2 -isopentenyl)adenine. On the basis of our results, we present a scheme summarizing the contribution of the main active forms of cytokinins, cytokinin receptors, and light to senescence regulation. We conclude that light can compensate the disrupted cytokinin signalling in detached leaves.

• Klíčová slova
• AHK, ahk mutants, chlorophyll, malondialdehyde, photosystem II,
• MeSH
• Arabidopsis metabolismus   účinky záření   MeSH
• chlorofyl metabolismus   MeSH
• cytokininy metabolismus   MeSH
• fotosystém II - proteinový komplex metabolismus   MeSH
• listy rostlin metabolismus   účinky záření   MeSH
• malondialdehyd metabolismus   MeSH
• peroxidace lipidů MeSH
• stárnutí metabolismus   účinky záření   MeSH
• světlo MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• chlorofyl MeSH
• cytokininy MeSH
• fotosystém II - proteinový komplex MeSH
• malondialdehyd MeSH