Leaf senescence, accompanied by chlorophyll breakdown, chloroplast degradation and inhibition of photosynthesis, can be suppressed by an exogenous application of cytokinins. Two aromatic cytokinin arabinosides (6-benzylamino-9-β-d-arabinofuranosylpurines; BAPAs), 3-hydroxy- (3OHBAPA) and 3-methoxy- (3MeOBAPA) derivatives, have recently been found to possess high anti-senescence activity. Interestingly, their effect on the maintenance of chlorophyll content and maximal quantum yield of photosystem II (PSII) in detached dark-adapted leaves differed quantitatively in wheat (Triticum aestivum L. cv. Aranka) and Arabidopsis (Arabidopsisthaliana L. (Col-0)). In this work, we have found that the anti-senescence effects of 3OHBAPA and 3MeOBAPA in wheat and Arabidopsis also differ in other parameters, including the maintenance of carotenoid content and chloroplasts, rate of reduction of primary electron acceptor of PSII (QA) as well as electron transport behind QA, and partitioning of absorbed light energy in light-adapted leaves. In wheat, 3OHBAPA had a higher protective effect than 3MeOBAPA, whereas in Arabidopsis, 3MeOBAPA was the more efficient derivative. We have found that the different anti-senescent activity of 3OHBAPA and 3MeOBAPA was coupled to different ethylene production in the treated leaves: the lower the ethylene production, the higher the anti-senescence activity. 3OHBAPA and 3MeOBAPA also efficiently protected the senescing leaves of wheat and Arabidopsis against oxidative damage induced by both H2O2 and high-light treatment, which could also be connected with the low level of ethylene production.
- MeSH
- Arabidopsis účinky léků růst a vývoj metabolismus MeSH
- cytokininy farmakologie MeSH
- ethyleny metabolismus MeSH
- fotosyntéza MeSH
- listy rostlin účinky léků růst a vývoj metabolismus MeSH
- pšenice účinky léků růst a vývoj metabolismus MeSH
- regulátory růstu rostlin farmakologie MeSH
- stárnutí buněk * MeSH
- Publikační typ
- časopisecké články MeSH
Cytokinins are plant hormones with biological functions ranging from coordination of plant growth to the regulation of biotic and abiotic stress-related responses and senescence. The components of the plant immune system can learn from past elicitations by microbial pathogens and herbivores and adapt to new threats. It is known that plants can enter the primed state of enhanced defense induced by either natural or synthetic compounds. While the involvement of cytokinins in defense priming has been documented, no comprehensive model of their action has been provided to date. Here, we report the functional characterization of two aromatic cytokinin derivatives, 6-benzylaminopurine-9-arabinosides (BAPAs), 3-methoxy-BAPA and 3-hydroxy-BAPA, that proved to be effective in delaying senescence in detached leaves while having low interactions with the cytokinin pathway. An RNA-seq profiling study on Arabidopsis leaves treated with 3-methoxy-BAPA revealed that short and extended treatments with this compound shifted the transcriptional response markedly toward defense. Both treatments revealed upregulation of genes involved in processes associated with plant innate immunity such as cell wall remodeling and upregulation of specific MAP kinases, most importantly MPK11, which is a MAPK module involved in stress-related signaling during the pathogen-associated molecular patterns (PAMPs) response. In addition, elevated levels of JA and its metabolites, jasmonate/ethylene-driven upregulation of PLANT DEFENSIN 1.2 (PDF1.2) and other defensins, and also temporarily elevated levels of reactive oxygen species marked the plant response to 3-methoxy-BAPA treatment. Synergistic interactions were observed when plants were cotreated with 3-hydroxy-BAPA and the flagellin-derived bacterial PAMP peptide (flg22), leading to the enhanced expression of the PAMP-triggered immunity (PTI) marker gene FRK1. Our data collectively show that some BAPAs can sensitively prime the PTI responses in a low micromolar range of concentrations while having no observable negative effects on the overall fitness of the plant.
- MeSH
- Arabidopsis chemie metabolismus MeSH
- arabinonukleosidy chemie farmakologie MeSH
- cytokininy chemie farmakologie MeSH
- imunita rostlin účinky léků MeSH
- listy rostlin účinky léků MeSH
- MAP kinasový signální systém účinky léků MeSH
- mitogenem aktivované proteinkinasy genetika metabolismus MeSH
- molekulární struktura MeSH
- PAMP struktury farmakologie MeSH
- proteiny huseníčku genetika metabolismus MeSH
- regulace genové exprese u rostlin účinky léků MeSH
- vztahy mezi strukturou a aktivitou MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
An efficient synthetic route for the synthesis of 2H-pyrazolo[4,3-c]pyridines, primarily varying by the substituents at the 2-, 4- and 6-positions, is described here. A Sonogashira-type cross-coupling reaction was employed to yield 3-alkynyl-1H-pyrazole-4-carbaldehydes, ethanones and propanones from the corresponding 1H-pyrazol-3-yl trifluoromethanesulfonates. Subsequent treatment of the coupling products with dry ammonia afforded a versatile library of 2H-pyrazolo[4,3-c]pyridines, which were then evaluated for their cytotoxicity against K562 and MCF-7 cancer cell lines. The most potent of these compounds displayed low micromolar GI50 values in both cell lines. Active compounds induced dose-dependent cell-cycle arrest in mitosis, as shown by flow cytometric analysis of DNA content and phosphorylation of histone H3 at serine-10. Moreover, biochemical assays revealed increased activities of caspases-3/7 in treated cells, specific fragmentation of PARP-1, and phosphorylation of Bcl-2, collectively confirming apoptosis as the mechanism of cell death.
- MeSH
- antimitotika chemická syntéza chemie farmakologie MeSH
- antitumorózní látky chemická syntéza chemie farmakologie MeSH
- buněčná smrt účinky léků MeSH
- buňky K562 MeSH
- kontrolní body buněčného cyklu účinky léků MeSH
- léky antitumorózní - screeningové testy MeSH
- lidé MeSH
- MFC-7 buňky MeSH
- mitóza účinky léků MeSH
- molekulární struktura MeSH
- proliferace buněk účinky léků MeSH
- pyridiny chemie farmakologie MeSH
- vztah mezi dávkou a účinkem léčiva MeSH
- vztahy mezi strukturou a aktivitou MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Plant hormones cytokinins regulate various aspects of plant growth and development. For their positive effects on branching, delaying of senescence, nutrient remobilisation, flower and seed set control they became interesting substances in search for potential agrochemicals. From the 1970' of the last century exogenous application of cytokinins have been tested in field conditions to improve yield traits of world-wide important crops such as wheat, rice, maize, barley, and soybean. Despite the extensive testing summarized in this work, so far cytokinins haven't found their stable place among commercialized plant growth regulators, mainly due to the complexity of their effects. Here we bring an overview of the outcomes obtained in pot and field experiments using cytokinin exogenous treatments, summarize the ways of application and point to the affected traits in various field crops, vegetables, cotton and fruit trees. Further, we present here outcomes of field trials performed with a derivative of N(6)-benzyladenine, 2-chloro-6-(3-methoxybenzyl)aminopurine, in spring barley and winter wheat. The effect on yield forming traits such as number of tillers, grains per ear, number of ears and the final yield was evaluated and compared after spraying of the both crops in different phenological stages.
Jasmonates (JAs) are plant hormones that integrate external stress stimuli with physiological responses. (+)-7-iso-JA-L-Ile is the natural JA ligand of COI1, a component of a known JA receptor. The upstream JA biosynthetic precursor cis-(+)-12-oxo-phytodienoic acid (cis-(+)-OPDA) has been reported to act independently of COI1 as an essential signal in several stress-induced and developmental processes. Wound-induced increases in the endogenous levels of JA/JA-Ile are accompanied by two to tenfold increases in the concentration of OPDA, but its means of perception and metabolism are unknown. To screen for putative OPDA metabolites, vegetative tissues of flowering Arabidopsis thaliana were extracted with 25% aqueous methanol (v/v), purified by single-step reversed-phase polymer-based solid-phase extraction, and analyzed by high throughput mass spectrometry. This enabled the detection and quantitation of a low abundant OPDA analog of the biologically active (+)-7-iso-JA-L-Ile in plant tissue samples. Levels of the newly identified compound and the related phytohormones JA, JA-Ile and cis-(+)-OPDA were monitored in wounded leaves of flowering Arabidopsis lines (Col-0 and Ws) and compared to the levels observed in Arabidopsis mutants deficient in the biosynthesis of JA (dde2-2, opr3) and JA-Ile (jar1). The observed cis-(+)-OPDA-Ile levels varied widely, raising questions concerning its role in Arabidopsis stress responses.
- MeSH
- Arabidopsis chemie MeSH
- cyklopentany chemie izolace a purifikace MeSH
- diazoniové sloučeniny MeSH
- isoleucin analogy a deriváty chemie MeSH
- květy chemie MeSH
- listy rostlin metabolismus MeSH
- nenasycené mastné kyseliny chemie izolace a purifikace metabolismus MeSH
- oxylipiny chemie izolace a purifikace MeSH
- pyridiny MeSH
- regulátory růstu rostlin metabolismus MeSH
- stereoizomerie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Studies of metabolic and physiological bases of plant tolerance and hardening against drought are essential to improve genetic breeding programs, especially in productive species such as Pinus radiata. The exposure to different drought cycles is a highly effective tool that improves plant conditioning, but limited information is available about the mechanisms that modulate this process. To clarify this issue, six P. radiata breeds with well-known differences in drought tolerance were analyzed after two consecutive drought cycles. Survival rate, concentration of several metabolites such as free soluble amino acids and polyamines, and main plant hormones varied between them after drought hardening, while relative growth ratio and water potential at both predawn and dawn did not. Hardening induced a strong increase in total soluble amino acids in all breeds, accumulating mainly those implicated in the glutamate metabolism (GM), especially L-proline, in the most tolerant breeds. Other amino acids from GM such as γ-aminobutyric acid (GABA) and L-arginine (Arg) were also strongly increased. GABA pathway could improve the response against drought, whereas Arg acts as precursor for the synthesis of spermidine. This polyamine showed a positive relationship with the survival capacity, probably due to its role as antioxidant under stress conditions. Finally, drought hardening also induced changes in phytohormone content, showing each breed a different profile. Although all of them accumulated indole-3-acetic acid and jasmonic acid and reduced zeatin content in needles, significant differences were observed regarding abscisic acid, salicylic acid and mainly zeatin riboside. These results confirm that hardening is not only species-dependent but also an intraspecific processes controlled through metabolite changes.
