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
MAIN CONCLUSION: The present review summarizes current knowledge of the biosynthesis and biological importance of isoprenoid-derived plant signaling compounds. Cellular organisms use chemical signals for intercellular communication to coordinate their growth, development, and responses to environmental cues. The skeletons of majority of plant signaling molecules, mediators of plant intercellular 'broadcasting', are built from C5 units of isoprene and therefore belong to a huge and diverse group of natural substances called isoprenoids (terpenoids). They fill many important roles in nature. This review summarizes current knowledge of the biosynthesis and biological importance of a group of isoprenoid-derived plant signaling compounds.
- MeSH
- brassinosteroidy biosyntéza MeSH
- cytokininy biosyntéza MeSH
- gibereliny biosyntéza MeSH
- kyselina abscisová biosyntéza MeSH
- metabolické sítě a dráhy MeSH
- regulátory růstu rostlin biosyntéza MeSH
- rostliny metabolismus MeSH
- signální transdukce * MeSH
- terpeny metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
Legume mutants have shown the requirement for receptor-mediated cytokinin signaling in symbiotic nodule organogenesis. While the receptors are central regulators, cytokinin also is accumulated during early phases of symbiotic interaction, but the pathways involved have not yet been fully resolved. To identify the source, timing, and effect of this accumulation, we followed transcript levels of the cytokinin biosynthetic pathway genes in a sliding developmental zone ofLotus japonicusroots.LjIpt2andLjLog4were identified as the major contributors to the first cytokinin burst. The genetic dependence and Nod factor responsiveness of these genes confirm that cytokinin biosynthesis is a key target of the common symbiosis pathway. The accumulation ofLjIpt2andLjLog4transcripts occurs independent of theLjLhk1receptor during nodulation. Together with the rapid repression of both genes by cytokinin, this indicates thatLjIpt2andLjLog4contribute to, rather than respond to, the initial cytokinin buildup. Analysis of the cytokinin response using the synthetic cytokinin sensor,TCSn, showed that this response occurs in cortical cells before spreading to the epidermis inL. japonicusWhile mutant analysis identified redundancy in several biosynthesis families, we found that mutation ofLjIpt4limits nodule numbers. Overexpression ofLjIpt3orLjLog4alone was insufficient to produce the robust formation of spontaneous nodules. In contrast, overexpressing a complete cytokinin biosynthesis pathway leads to large, often fused spontaneous nodules. These results show the importance of cytokinin biosynthesis in initiating and balancing the requirement for cortical cell activation without uncontrolled cell proliferation.
- MeSH
- biologické modely MeSH
- cytokininy biosyntéza MeSH
- kořenové hlízky rostlin cytologie genetika růst a vývoj fyziologie MeSH
- kořeny rostlin cytologie genetika růst a vývoj fyziologie MeSH
- Lotus cytologie genetika růst a vývoj fyziologie MeSH
- regulace genové exprese u rostlin MeSH
- regulátory růstu rostlin biosyntéza MeSH
- Rhizobiaceae fyziologie MeSH
- rostlinné proteiny genetika metabolismus MeSH
- signální transdukce * MeSH
- symbióza MeSH
- tvorba kořenových hlízek MeSH
- vývojová regulace genové exprese genetika MeSH
- Publikační typ
- časopisecké články MeSH
Cytokinins are an important group of plant hormones that are also found in other organisms, including cyanobacteria. While various aspects of cytokinin function and metabolism are well understood in plants, the information is limited for cyanobacteria. In this study, we first experimentally confirmed a prenylation of tRNA by recombinant isopentenyl transferase NoIPT2 from Nostoc sp. PCC 7120, whose encoding gene we previously identified in Nostoc genome along with the gene for adenylate isopentenyl transferase NoIPT1. In contrast to NoIPT2, the transcription of NoIPT1 was strongly activated during the dark period and was followed by an increase in the cytokinin content several hours later in the light period. Dominant cytokinin metabolites detected at all time points were free bases and monophosphates of isopentenyladenine and cis-zeatin, while N-glucosides were not detected at all. Whole transcriptome differential expression analysis of cultures of the above Nostoc strain treated by cytokinin compared to untreated controls indicated that cytokinin together with light trigger expression of several genes related to signal transduction, including two-component sensor histidine kinases and two-component hybrid sensors and regulators. One of the affected histidine kinases with a cyclase/histidine kinase-associated sensory extracellular domain similar to the cytokinin-binding domain in plant cytokinin receptors was able to modestly bind isopentenyladenine. The data show that the genetic disposition allows Nostoc not only to produce free cytokinins and prenylate tRNA but also modulate the cytokinin biosynthesis in response to light, triggering complex changes in sensing and regulation.
Silicate minerals are dominant soil components. Thus, plant roots are constantly exposed to silicic acid. High silicon intake, enabled by root silicon transporters, correlates with increased tolerance to many biotic and abiotic stresses. However, the underlying protection mechanisms are largely unknown. Here, we tested the hypothesis that silicon interacts with the plant hormones, and specifically, that silicic acid intake increases cytokinin biosynthesis. The reaction of sorghum (Sorghum bicolor) and Arabidopsis plants, modified to absorb high versus low amounts of silicon, to dark-induced senescence was monitored, by quantifying expression levels of genes along the senescence pathway and measuring tissue cytokinin levels. In both species, detached leaves with high silicon content senesced more slowly than leaves that were not exposed to silicic acid. Expression levels of genes along the senescence pathway suggested increased cytokinin biosynthesis with silicon exposure. Mass spectrometry measurements of cytokinin suggested a positive correlation between silicon exposure and active cytokinin concentrations. Our results indicate a similar reaction to silicon treatment in distantly related plants, proposing a general function of silicon as a stress reliever, acting via increased cytokinin biosynthesis.
- MeSH
- Arabidopsis účinky léků genetika metabolismus MeSH
- cytokininy biosyntéza MeSH
- geneticky modifikované rostliny MeSH
- kořeny rostlin metabolismus MeSH
- křemík metabolismus farmakologie MeSH
- listy rostlin účinky léků metabolismus fyziologie MeSH
- mutace MeSH
- regulace genové exprese u rostlin MeSH
- Sorghum účinky léků genetika metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
Transporter genes and cytokinins are key targets for crop improvement. These genes are active during the development of the seed and its establishment as a strong sink. However, during germination, the seed transitions to being a source for the developing root and shoot. To determine if the sucrose transporter (SUT), amino acid permease (AAP), Sugar Will Eventually be Exported Transporter (SWEET), cell wall invertase (CWINV), cytokinin biosynthesis (IPT), activation (LOG) and degradation (CKX) gene family members are involved in both the sink and source activities of seeds, we used RT-qPCR to determine the expression of multiple gene family members, and LC-MS/MS to ascertain endogenous cytokinin levels in germinating Pisum sativum L. We show that genes that are actively expressed when the seed is a strong sink during its development, are also expressed when the seed is in the reverse role of being an active source during germination and early seedling growth. Cytokinins were detected in the imbibing seeds and were actively biosynthesised during germination. We conclude that, when the above gene family members are targeted for seed yield improvement, a downstream effect on subsequent seed germination or seedling vigour must be taken into consideration.
- MeSH
- buněčná stěna enzymologie MeSH
- cytokininy biosyntéza genetika MeSH
- hrách setý genetika růst a vývoj MeSH
- invertasa biosyntéza genetika MeSH
- klíčení genetika MeSH
- proteiny přenášející monosacharidy biosyntéza genetika MeSH
- regulace genové exprese u rostlin MeSH
- regulátory růstu rostlin genetika MeSH
- semena rostlinná genetika růst a vývoj MeSH
- semenáček genetika MeSH
- tandemová hmotnostní spektrometrie MeSH
- transportní systémy aminokyselin biosyntéza genetika MeSH
- Publikační typ
- časopisecké články MeSH
Plant beneficial microbes mediate biocontrol of diseases by interfering with pathogens or via strengthening the host. Although phytohormones, including cytokinins, are known to regulate plant development and physiology as well as plant immunity, their production by microorganisms has not been considered as a biocontrol mechanism. Here we identify the ability of Pseudomonas fluorescens G20-18 to efficiently control P. syringae infection in Arabidopsis, allowing maintenance of tissue integrity and ultimately biomass yield. Microbial cytokinin production was identified as a key determinant for this biocontrol effect on the hemibiotrophic bacterial pathogen. While cytokinin-deficient loss-of-function mutants of G20-18 exhibit impaired biocontrol, functional complementation with cytokinin biosynthetic genes restores cytokinin-mediated biocontrol, which is correlated with differential cytokinin levels in planta. Arabidopsis mutant analyses revealed the necessity of functional plant cytokinin perception and salicylic acid-dependent defence signalling for this biocontrol mechanism. These results demonstrate microbial cytokinin production as a novel microbe-based, hormone-mediated concept of biocontrol. This mechanism provides a basis to potentially develop novel, integrated plant protection strategies combining promotion of growth, a favourable physiological status and activation of fine-tuned direct defence and abiotic stress resilience.
- MeSH
- Arabidopsis mikrobiologie MeSH
- cytokininy analýza biosyntéza farmakologie MeSH
- kyselina salicylová farmakologie MeSH
- listy rostlin mikrobiologie MeSH
- nemoci rostlin mikrobiologie MeSH
- Pseudomonas fluorescens metabolismus MeSH
- Pseudomonas syringae účinky léků růst a vývoj patogenita MeSH
- regulátory růstu rostlin farmakologie MeSH
- tandemová hmotnostní spektrometrie MeSH
- vysokoúčinná kapalinová chromatografie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Disease symptoms of some phytopathogenic fungi are associated with changes in cytokinin (CK) levels. Here, we show that the CK profile of ergot-infected rye plants is also altered, although no pronounced changes occur in the expression of the host plant's CK biosynthesis genes. Instead, we demonstrate a clearly different mechanism: we report on the first fungal de novo CK biosynthesis genes, prove their functions and constitute a biosynthetic pathway. The ergot fungus Claviceps purpurea produces substantial quantities of CKs in culture and, like plants, expresses enzymes containing the isopentenyltransferase and lonely guy domains necessary for de novo isopentenyladenine production. Uniquely, two of these domains are combined in one bifunctional enzyme, CpIPT-LOG, depicting a novel and potent mechanism for CK production. The fungus also forms trans-zeatin, a reaction catalysed by a CK-specific cytochrome P450 monooxygenase, which is encoded by cpp450 forming a small cluster with cpipt-log. Deletion of cpipt-log and cpp450 did not affect virulence of the fungus, but Δcpp450 mutants exhibit a hyper-sporulating phenotype, implying that CKs are environmental factors influencing fungal development.
- MeSH
- alkyltransferasy a aryltransferasy metabolismus MeSH
- Claviceps genetika růst a vývoj metabolismus MeSH
- cytokininy biosyntéza MeSH
- delece genu MeSH
- geny hub genetika MeSH
- isopentenyladenosin biosyntéza MeSH
- rostlinné geny genetika MeSH
- systém (enzymů) cytochromů P-450 genetika MeSH
- žito mikrobiologie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Shoot branching is a primary contributor to plant architecture, evolving independently in flowering plant sporophytes and moss gametophytes. Mechanistic understanding of branching is largely limited to flowering plants such as Arabidopsis, which have a recent evolutionary origin. We show that in gametophytic shoots of Physcomitrella, lateral branches arise by re-specification of epidermal cells into branch initials. A simple model co-ordinating the activity of leafy shoot tips can account for branching patterns, and three known and ancient hormonal regulators of sporophytic branching interact to generate the branching pattern- auxin, cytokinin and strigolactone. The mode of auxin transport required in branch patterning is a key divergence point from known sporophytic pathways. Although PIN-mediated basipetal auxin transport regulates branching patterns in flowering plants, this is not so in Physcomitrella, where bi-directional transport is required to generate realistic branching patterns. Experiments with callose synthesis inhibitors suggest plasmodesmal connectivity as a potential mechanism for transport.
- MeSH
- biologické modely MeSH
- biologický transport účinky léků MeSH
- cytokininy biosyntéza MeSH
- epidermis rostlin cytologie růst a vývoj MeSH
- geneticky modifikované rostliny MeSH
- kyseliny indoloctové metabolismus farmakologie MeSH
- laktony farmakologie MeSH
- mechy účinky léků růst a vývoj MeSH
- morfogeneze účinky léků MeSH
- mutace genetika MeSH
- regulace genové exprese u rostlin účinky léků MeSH
- regulátory růstu rostlin farmakologie MeSH
- rostlinné proteiny metabolismus MeSH
- rozvržení tělního plánu účinky léků MeSH
- výhonky rostlin účinky léků růst a vývoj MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
One of several roles of the Mycobacterium tuberculosis proteasome is to defend against host-produced nitric oxide (NO), a free radical that can damage numerous biological macromolecules. Mutations that inactivate proteasomal degradation in Mycobacterium tuberculosis result in bacteria that are hypersensitive to NO and attenuated for growth in vivo, but it was not known why. To elucidate the link between proteasome function, NO resistance, and pathogenesis, we screened for suppressors of NO hypersensitivity in a mycobacterial proteasome ATPase mutant and identified mutations in Rv1205. We determined that Rv1205 encodes a pupylated proteasome substrate. Rv1205 is a homolog of the plant enzyme LONELY GUY, which catalyzes the production of hormones called cytokinins. Remarkably, we report that an obligate human pathogen secretes several cytokinins. Finally, we determined that the Rv1205-dependent accumulation of cytokinin breakdown products is likely responsible for the sensitization of Mycobacterium tuberculosis proteasome-associated mutants to NO.
- MeSH
- aldehydy metabolismus MeSH
- aminohydrolasy genetika metabolismus MeSH
- bakteriální proteiny chemie metabolismus MeSH
- cytokininy biosyntéza metabolismus MeSH
- interakce hostitele a patogenu MeSH
- mutace MeSH
- Mycobacterium tuberculosis účinky léků genetika metabolismus patogenita MeSH
- myši inbrední C57BL MeSH
- oxid dusnatý metabolismus farmakologie MeSH
- proteasomový endopeptidasový komplex metabolismus MeSH
- proteiny huseníčku metabolismus MeSH
- suprese genetická MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
