In plants, γ-aminobutyric acid (GABA) accumulates rapidly in response to environmental stress and variations in its endogenous concentration have been shown to affect plant growth. Exogenous application of GABA has also conferred higher stress tolerance by modulating the expression of genes involved in plant signalling, transcriptional regulation, hormone biosynthesis, reactive oxygen species production and polyamine metabolism. Plant hormones play critical roles in adaptation of plants to adverse environmental conditions through a sophisticated crosstalk among them. Several studies have provided evidence for the relationships between GABA, polyamines and hormones such as abscisic acid, cytokinins, auxins, gibberellins and ethylene, among others, focussing on the effect that one specific group of compounds exerts over the metabolic and signalling pathways of others. In this review, we bring together information obtained from plants exposed to several stress conditions and discuss the possible links among these different groups of molecules. The analysis supports the view that highly conserved pathways connect primary and secondary metabolism, with an overlap of regulatory functions related to stress responses and tolerance among phytohormones, amino acids and polyamines.
- MeSH
- cytokininy metabolismus MeSH
- fyziologická adaptace MeSH
- fyziologický stres MeSH
- GABA metabolismus MeSH
- kyselina abscisová metabolismus MeSH
- kyseliny indoloctové metabolismus MeSH
- metabolické sítě a dráhy MeSH
- polyaminy metabolismus MeSH
- regulátory růstu rostlin metabolismus MeSH
- rostliny metabolismus MeSH
- signální transdukce MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
MAIN CONCLUSION: Isoprenoid and aromatic cytokinins occur in poplar as free compounds and constituents of tRNA, poplar isopentenyltransferases are involved in the production of isoprenoid cytokinins, while biosynthesis of their aromatic counterparts remains unsolved. Cytokinins are phytohormones with a fundamental role in the regulation of plant growth and development. They occur naturally either as isoprenoid or aromatic derivatives, but the latter are quite rare and less studied. Here, the spatial expression of all nine isopentenyl transferase genes of Populus × canadensis cv. Robusta (PcIPTs) as analyzed by RT-qPCR revealed a tissue preference and strong differences in expression levels for the different adenylate and tRNA PcIPTs. Together with their phylogeny, this result suggests a functional diversification for the different PcIPT proteins. Additionally, the majority of PcIPT genes were cloned and expressed in Arabidopsis thaliana under an inducible promoter. The cytokinin levels measured in the Arabidopsis-overexpressing lines as well as their phenotype indicate that the studied adenylate and tRNA PcIPT proteins are functional in vivo and thus will contribute to the cytokinin pool in poplar. We screened the cytokinin content in leaves of 12 Populus species by ultra-high performance-tandem mass spectrometry (UHPLC-MS/MS) and discovered that the capacity to produce not only isoprenoid, but also aromatic cytokinins is widespread amongst the Populus accessions studied. Important for future studies is that the levels of aromatic cytokinins transiently increase after daybreak and are much higher in older plants.
- MeSH
- alkyltransferasy a aryltransferasy genetika metabolismus MeSH
- Arabidopsis genetika metabolismus MeSH
- cytokininy biosyntéza MeSH
- fylogeneze MeSH
- geneticky modifikované rostliny MeSH
- listy rostlin genetika metabolismus MeSH
- Populus genetika metabolismus MeSH
- regulátory růstu rostlin metabolismus MeSH
- rostlinné proteiny genetika metabolismus MeSH
- tandemová hmotnostní spektrometrie MeSH
- Publikační typ
- časopisecké články MeSH
The moss Physcomitrella patens is part of an early divergent clade of land plants utilizing the plant hormone cytokinin for growth control. The rate-limiting step of cytokinin biosynthesis is mediated by isopentenyltransferases (IPTs), found in land plants either as adenylate-IPTs or as tRNA-IPTs. Although a dominant part of cytokinins in flowering plants are synthesized by adenylate-IPTs, the Physcomitrella genome only encodes homologues of tRNA-IPTs. This study therefore looked into the question of whether cytokinins in moss derive from tRNA exclusively. Targeted gene knockout of ipt1 (d|ipt1) along with localization studies revealed that the chloroplast-bound IPT1 was almost exclusively responsible for the A37 prenylation of tRNA in Physcomitrella. Ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS)-based cytokinin profiling demonstrated that the total amount of all free cytokinins in tissue was almost unaffected. However, the knockout plants showed increased levels of the N (6) -isopentenyladenine (iP)- and trans-zeatin (tZ)-type cytokinins, considered to provide active forms, while cis-zeatin (cZ)-type cytokinins were reduced. The data provide evidence for an additional and unexpected tRNA-independent cytokinin biosynthetic pathway in moss. Comprehensive phylogenetic analysis indicates a diversification of tRNA-IPT-like genes in bryophytes probably related to additional functions.
- MeSH
- alkyltransferasy a aryltransferasy genetika metabolismus MeSH
- biologická evoluce * MeSH
- chloroplasty enzymologie genetika MeSH
- cytokininy biosyntéza MeSH
- fylogeneze * MeSH
- genový knockout MeSH
- mechy klasifikace enzymologie genetika MeSH
- molekulární sekvence - údaje MeSH
- RNA transferová genetika metabolismus MeSH
- rostlinné proteiny genetika metabolismus MeSH
- rostliny klasifikace enzymologie genetika MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Phytohormones are key regulators in various physiological processes of plant growth and development. Their chemical analyses, together with their genomics and proteomics, are an integral part of plant development studies. The information on hormone levels is often valuable for biologists dealing with any hormone-regulated processes. Plant tissue is a complex multicomponent mixture containing phytohormones in minute quantities (pg or ng/g fresh weight) along with many other related compounds with similar structures and/or physicochemical properties. Therefore, their analysis requires rapid, sensitive and sufficiently selective analytical methods. The significance of solid-phase extraction for purification and hyphenated techniques such as GC-MS, LC-MS and CE-MS for routine analyses of phytohormones is discussed.
- MeSH
- Brassica MeSH
- chemické techniky analytické MeSH
- chromatografie kapalinová MeSH
- cyklopentany analýza MeSH
- cytokininy analýza MeSH
- elektroforéza kapilární MeSH
- financování organizované MeSH
- fyziologie rostlin MeSH
- gibereliny analýza MeSH
- kyselina abscisová analýza MeSH
- kyseliny indoloctové analýza MeSH
- plynová chromatografie s hmotnostně spektrometrickou detekcí MeSH
- rostliny MeSH
- steroidy MeSH
BACKGROUND: When applied to a nutrition solution or agar media, the non-substituted aromatic cytokinins caused thickening and shortening of the primary root, had an inhibitory effect on lateral root branching, and even showed some negative effects on development of the aerial part at as low as a 10 nanomolar concentration. Novel analogues of aromatic cytokinins ranking among topolins substituted on N9-atom of adenine by tetrahydropyranyl or 4-chlorobutyl group have been prepared and tested in standardized cytokinin bioassays [1]. Those showing comparable activities with N(6)-benzylaminopurine were further tested in planta. METHODOLOGY/PRINCIPAL FINDINGS: The main aim of the study was to explain molecular mechanism of function of novel cytokinin derivatives on plant development. Precise quantification of cytokinin content and profiling of genes involved in cytokinin metabolism and perception in treated plants revealed several aspects of different action of m-methoxytopolin base and its substituted derivative on plant development. In contrast to standard cytokinins, N9- tetrahydropyranyl derivative of m-topolin and its methoxy-counterpart showed the negative effects on root development only at three orders of magnitude higher concentrations. Moreover, the methoxy-derivative demonstrates a positive effect on lateral root branching and leaf emerging in a nanomolar range of concentrations, in comparison with untreated plants. CONCLUSIONS/SIGNIFICANCE: Tetrahydropyranyl substitution at N9-position of cytokinin purine ring significantly enhances acropetal transport of a given cytokinins. Together with the methoxy-substitution, impedes accumulation of non-active cytokinin glucoside forms in roots, allows gradual release of the active base, and has a significant effect on the distribution and amount of endogenous isoprenoid cytokinins in different plant tissues. The utilization of novel aromatic cytokinin derivatives can distinctively improve expected hormonal effects in plant propagation techniques in the future.
- MeSH
- aktivace enzymů MeSH
- Arabidopsis účinky léků genetika růst a vývoj metabolismus MeSH
- biomasa MeSH
- cytokininy chemie farmakologie MeSH
- kořeny rostlin chemie účinky léků růst a vývoj MeSH
- kukuřice setá účinky léků genetika růst a vývoj metabolismus MeSH
- listy rostlin chemie účinky léků růst a vývoj MeSH
- oxidoreduktasy metabolismus MeSH
- proliferace buněk účinky léků MeSH
- regulace genové exprese u rostlin MeSH
- regulátory růstu rostlin chemie farmakologie MeSH
- semenáček účinky léků MeSH
- stanovení celkové genové exprese MeSH
- xylém chemie metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
