BACKGROUND: Cytokinin is a negative regulator of root growth, and a reduction of the cytokinin content or signalling causes the formation a larger root system in model plants, improves their growth under drought and nutrient limitation and causes increased accumulation of elements in the shoot. Roots are an important but understudied target of plant breeding. Here we have therefore explored whether root enhancement by lowering the cytokinin content can also be achieved in oilseed rape (Brassica napus L.) plants. RESULTS: Transgenic plants overexpressing the CKX2 gene of Arabidopsis thaliana encoding a cytokinin-degrading cytokinin oxidase/dehydrogenase showed higher CKX activity and a strongly reduced cytokinin content. Cytokinin deficiency led to the formation of a larger root system under different growth conditions, which was mainly due to an increased number of lateral and adventitious roots. In contrast, shoot growth was comparable to wild type, which caused an enhanced root-to-shoot ratio. Transgenic plants accumulated in their leaves higher concentrations of macro- and microelements including P, Ca, Mg, S, Zn, Cu, Mo and Mn. They formed more chlorophyll under Mg- and S-deficiency and accumulated a larger amount of Cd and Zn from contaminated medium and soil. CONCLUSIONS: These findings demonstrate the usefulness of ectopic CKX gene expression to achieve root enhancement in oilseed rape and underpin the functional relevance of a larger root system. Furthermore, the lack of major developmental consequences on shoot growth in cytokinin-deficient oilseed rape indicates species-specific differences of CKX gene and/or cytokinin action.

• MeSH
• biodegradace * MeSH
• Brassica napus genetika   růst a vývoj   metabolismus   MeSH
• chlorofyl analýza   metabolismus   MeSH
• cytokininy genetika   metabolismus   MeSH
• geneticky modifikované rostliny MeSH
• kadmium analýza   metabolismus   MeSH
• kořeny rostlin růst a vývoj   metabolismus   MeSH
• listy rostlin chemie   metabolismus   MeSH
• oxidoreduktasy genetika   metabolismus   MeSH
• půda chemie   MeSH
• zinek analýza   metabolismus   MeSH
• živiny analýza   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH

The long-standing Acid Growth Theory of plant cell elongation posits that auxin promotes cell elongation by stimulating cell wall acidification and thus expansin action. To date, the paucity of pertinent genetic materials has precluded thorough analysis of the importance of this concept in roots. The recent isolation of mutants of the model grass species Brachypodium distachyon with dramatically enhanced root cell elongation due to increased cellular auxin levels has allowed us to address this question. We found that the primary transcriptomic effect associated with elevated steady state auxin concentration in elongating root cells is upregulation of cell wall remodeling factors, notably expansins, while plant hormone signaling pathways maintain remarkable homeostasis. These changes are specifically accompanied by reduced cell wall arabinogalactan complexity but not by increased proton excretion. On the contrary, we observed a tendency for decreased rather than increased proton extrusion from root elongation zones with higher cellular auxin levels. Moreover, similar to Brachypodium, root cell elongation is, in general, robustly buffered against external pH fluctuation in Arabidopsis thaliana However, forced acidification through artificial proton pump activation inhibits root cell elongation. Thus, the interplay between auxin, proton pump activation, and expansin action may be more flexible in roots than in shoots.

• MeSH
• Brachypodium metabolismus   MeSH
• buněčná stěna metabolismus   MeSH
• galaktany metabolismus   MeSH
• kořeny rostlin metabolismus   MeSH
• kyseliny indoloctové metabolismus   MeSH
• signální transdukce fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH

The Eda pathway ( Eda, Edar, Edaradd) plays an important role in tooth development, determining tooth number, crown shape, and enamel formation. Here we show that the Eda pathway also plays a key role in root development. Edar (the receptor) is expressed in Hertwig's epithelial root sheath (HERS) during root development, with mutant mice showing a high incidence of taurodontism: large pulp chambers lacking or showing delayed bifurcation or trifurcation of the roots. The mouse upper second molars in the Eda pathway mutants show the highest incidence of taurodontism, this enhanced susceptibility being matched in human patients with mutations in EDA-A1. These taurodont teeth form due to defects in the direction of extension of the HERS from the crown, associated with a more extensive area of proliferation of the neighboring root mesenchyme. In those teeth where the angle at which the HERS extends from the crown is very wide and therefore more vertical, the mutant HERSs fail to reach toward the center of the tooth in the normal furcation region, and taurodont teeth are created. The phenotype is variable, however, with milder changes in angle and proliferation leading to normal or delayed furcation. This is the first analysis of the role of Eda in the root, showing a direct role for this pathway during postnatal mouse development, and it suggests that changes in proliferation and angle of HERS may underlie taurodontism in a range of syndromes.

• MeSH
• abnormality zubů genetika   MeSH
• dítě MeSH
• ektodysplasiny genetika   MeSH
• fenotyp MeSH
• kavita zubní dřeně abnormality   MeSH
• lidé MeSH
• mladiství MeSH
• moláry abnormality   embryologie   MeSH
• myši MeSH
• odontogeneze genetika   MeSH
• rentgenová mikrotomografie MeSH
• signální transdukce MeSH
• zubní kořen abnormality   embryologie   MeSH
• zvířata MeSH
• Check Tag
• dítě MeSH
• lidé MeSH
• mladiství MeSH
• mužské pohlaví MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

Úvod: V současné dynamicky se rozvíjející endodoncii dochází k neustálému vývoji nových postupů ošetření a s tím souvisí i požadavky na kvalitní a spolehlivé materiály potřebné k zaplnění kořenového systému zubu. Před několika lety byly uvedeny na trh nové typy kořenových sealerů na bázi kalciumsilikátových sloučenin, které by mohly splňovat většinu parametrů dokonalého pečeticího materiálu. Novější generace těchto sealerů obsahují příměs kalciumfosfátu a jsou v zahraniční literatuře označovány jako biokeramické sealery. Cílem sdělení je objasnit problematiku této skupiny sealerů a popsat jejich chemické, fyzikální a biologické vlastnosti. Sealery na bázi biokeramických sloučenin mají mnoho společných charakteristik s původním materiálem MTA (mineral trioxide aggregate). Vynikají především hydrofilním profilem a schopností tuhnout ve vlhkém prostředí. V kontaktu s dentinem dochází na jejich povrchu k depozici precipitátů hydroxyapatitu, a tím je potencováno spolehlivé zapečetění kořenového kanálku. Z fyzikálního hlediska jsou objemově stálé a při tuhnutí byla prokázána mírná expanze. Vlhkost prostředí a vysoká afinita k vodě podporují biomineralizační pochody ve tkáních, což spolu s dobrou zatékavostí materiálu umožňuje vyplnit celý prostor kořenového kanálku včetně jeho nepravidelností. Biokompatibilita, schopnost hojení rány a nízká cytotoxicita činí tento typ sealerů vhodný pro trvalý kontakt s tkáněmi periodoncia, kde je prolongovaným uvolňováním vápenatých iontů podporována regenerace. Bylo prokázáno, že díky vysoké hodnotě pH při tuhnutí působí tyto typy sealerů rovněž antimikrobiálně. Pro klinické využití mají dostatečnou rentgen kontrastnost, avšak podle použitého radioopakního aditiva vykazují v různé míře tendenci k dys-koloracím tvrdých zubních tkání. Relativně nevýhodnou vlastností mohou rovněž být zvýšená rozpustnost, porozita a nasákavost vody. Vzhledem k dynamické a bioaktivní povaze těchto sealerů však tyto nepříznivé vlastnosti nemusí být významné pro úspěšnost ošetření v klinické praxi. Mechanické vlastnosti většiny biokeramických sealerů obecně negativně ovlivňuje aplikace tepla, proto jsou pro klinické použití doporučovány kondenzační techniky plnění kořenových kanálků za studena. Závěr: Výstupy klinických a experimentálních studií vyzdvihují výhodné vlastnosti a spolehlivost skupiny sealerů na bázi kalciumsilikátových sloučenin a naznačují do budoucna slibné výsledky při praktickém využití nejen ve specializovaných endodontických praxích.

Introduction: In modern endodontics, there is a constant development of new procedures and requirements for high-quality and reliable materials to fill the root canal system are rising. A few years ago, a new types of calcium silicate-based root canal sealers were launched on the market, which could meet most of the parameters of a perfect sealing material. Newer generations of these sealers contain calcium phosphate and are also referred to in the literature worldwide as bioceramic sealers. Aim of the article: The aim of this article is to present the characteristics of this group of sealers and to outline their chemical, physical and biological properties. Bioceramicbased root canal sealers have many characteristics in common with the original material MTA (mineral trioxide aggregate). They are similar to its chemical composition and setting reaction. They are hydrophilic and able to set in humid environments. In contact with the dentin, hydroxyapatite crystals are deposited on the surface, thus enhancing the sealing ability of the root canal. Considering their physical characteristics, they are volumetrically stable and there is even a slight expansion during material setting. Humidity of the environment and high water sorption promote the biomineralization processes, and contribute to a better seal of the root canal. The flowability of the material allows to fill the entire space of the root canal, even including its irregularities. Biocompatibility, wound healing ability and minimal cytotoxicity make this type of sealer suitable for permanent contact with periodontal tissues, where prolonged release of calcium ions promotes regeneration. High pH value during material setting result in an antimicrobial effect. They have sufficient X-ray contrast for clinical use, but depending on the radiopaque additive used, they show a tendency to discoloration of hard dental tissues. A relatively disadvantageous features are increased solubility, porosity and water absorption. However, due to the dynamic and bioactive nature of these sealers, these adverse properties may not be significant for the success of treatment in clinical practice. The mechanical properties of most bioceramic sealers are generally negatively affected by heat. Due to this fact, cold obturation methods are recommended for bioceramic-based sealers. Conclusion: The outcomes of clinical and experimental studies generally highlight the beneficial properties and reliability of this group of sealers. They suggest promising results not only in specialized endodontic practices.

• Klíčová slova
• biokeramický sealer, kalciumsilikátový sealer,
• MeSH
• lidé MeSH
• výplňové materiály kořenových kanálků * MeSH
• zubní porcelán MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• přehledy MeSH

Zinc (Zn) is an essential element in human nutrition. The concentration of Zn in cereals, which is a staple food in developing countries, is often too low thus contributing to Zn malnutrition in nearly two billion people worldwide. We have reported recently that transgenic barley plants expressing a cytokinin-degrading CYTOKININ OXIDASE/DEHYDROGENASE (CKX) gene in their roots form a larger root system and accumulate a higher concentration of Zn in their grains when grown under greenhouse conditions. Here, we have tested this trait under field conditions. Four independent pEPP:CKX lines accumulated an up to 30% higher Zn concentration in their grains as compared to the untransformed control suggesting that this is a stable trait. The increased Zn concentration exceeded the limit set by the HarvestPlus program for wheat. We, therefore, propose that root enhancement achieved by increased degradation of cytokinin in roots can be a sustainable strategy to combat malnutrition caused by Zn deficiency.

• MeSH
• cytokininy metabolismus   MeSH
• geneticky modifikované rostliny genetika   metabolismus   MeSH
• ječmen (rod) genetika   metabolismus   MeSH
• jedlá semena genetika   metabolismus   MeSH
• kořeny rostlin genetika   metabolismus   MeSH
• oxidoreduktasy genetika   metabolismus   MeSH
• rostlinné proteiny genetika   metabolismus   MeSH
• zinek metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Auxin is necessary for the inhibition of root growth induced by aluminium (Al) stress, however the molecular mechanism controlling this is largely unknown. Here, we report that YUCCA (YUC), which encodes flavin monooxygenase-like proteins, regulates local auxin biosynthesis in the root apex transition zone (TZ) in response to Al stress. Al stress up-regulates YUC3/5/7/8/9 in the root-apex TZ, which we show results in the accumulation of auxin in the root-apex TZ and root-growth inhibition during the Al stress response. These Al-dependent changes in the regulation of YUCs in the root-apex TZ and YUC-regulated root growth inhibition are dependent on ethylene signalling. Increasing or disruption of ethylene signalling caused either enhanced or reduced up-regulation, respectively, of YUCs in root-apex TZ in response to Al stress. In addition, ethylene enhanced root growth inhibition under Al stress was strongly alleviated in yuc mutants or by co-treatment with yucasin, an inhibitor of YUC activity, suggesting a downstream role of YUCs in this process. Moreover, ethylene-insensitive 3 (EIN3) is involved into the direct regulation of YUC9 transcription in this process. Furthermore, we demonstrated that PHYTOCHROME INTERACTING FACTOR4 (PIF4) functions as a transcriptional activator for YUC5/8/9. PIF4 promotes Al-inhibited primary root growth by regulating the local expression of YUCs and auxin signal in the root-apex TZ. The Al-induced expression of PIF4 in root TZ acts downstream of ethylene signalling. Taken together, our results highlight a regulatory cascade for YUCs-regulated local auxin biosynthesis in the root-apex TZ mediating root growth inhibition in response to Al stress.

• MeSH
• aktivace transkripce genetika   MeSH
• Arabidopsis účinky léků   genetika   růst a vývoj   MeSH
• ethyleny metabolismus   MeSH
• fyziologický stres genetika   MeSH
• hliník toxicita   MeSH
• jaderné proteiny genetika   metabolismus   MeSH
• kořeny rostlin účinky léků   genetika   růst a vývoj   MeSH
• kyseliny indoloctové metabolismus   MeSH
• oxygenasy genetika   MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• regulace genové exprese u rostlin účinky léků   MeSH
• signální transdukce genetika   MeSH
• transkripční faktory bHLH genetika   metabolismus   MeSH
• transkripční faktory genetika   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH

Arbuscular mycorrhizas (AMs) have the ability to enhance drought tolerance of citrus, but the underlying mechanisms have not been clearly elucidated. Considering the strong association of cell membrane fatty acid (FA) unsaturation with plant drought tolerance, the present study hypothesized that AM fungi (AMF) modulated the composition and unsaturation of FAs to enhance drought tolerance of host plants. Drought-sensitive citrus rootstocks, trifoliate orange (Poncirus trifoliata) seedlings, were inoculated with AMF (Funneliformis mosseae) for 3 months and were subsequently exposed to drought stress (DS) for 8 weeks. Mycorrhizal seedlings exhibited better plant growth performance, higher leaf water potential and lower root abscisic acid concentrations under both well-watered (WW) and DS conditions. Arbuscular mycorrhiza fungus inoculation considerably increased root methyl oleate (C18:1), methyl linoleate (C18:2) and methyl linolenate (C18:3N3) concentrations under both WW and DS conditions, and root methyl palmitoleate (C16:1) concentrations under WW, while it decreased root methyl stearate (C18:0) levels under both WW and DS. These changes in the composition of FAs of mycorrhized roots resulted in higher unsaturation index of root FAs, which later aided in reducing the oxidative damage on account of lower concentration of malondialdehyde and superoxide radicals. The changes of these FAs were a result of AMF-up-regulating root FA desaturase 2 (PtFAD2), FA desaturase 6 (PtFAD6) and Δ9 FA desaturase (PtΔ9) genes under WW and PtFAD2, PtFAD6 and Δ15 FA desaturase (PtΔ15) genes under DS conditions. Our results confirmed that mycorrhization brought significant changes in root FA compositions, in addition to regulation of gene expression responsible for increasing the unsaturation level of FAs, a predisposing physiological event for better drought tolerance of citrus.

• MeSH
• Citrus * MeSH
• Glomeromycota * MeSH
• kořeny rostlin MeSH
• mykorhiza * MeSH
• období sucha MeSH
• Poncirus * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Terrestrial plants typically take up nutrients through roots or mycorrhizae while freshwater plants additionally utilize leaves. Their nutrient uptake may be enhanced by root hairs whose occurrence is often negatively correlated with mycorrhizal colonization. Seagrasses utilize both leaves and roots and often form root hairs, but seem to be devoid of mycorrhizae. The Mediterranean seagrass Posidonia oceanica is an exception: its adults commonly lack root hairs and regularly form a specific association with a single pleosporalean fungus. Here we show that at two sites in the southern Adriatic, all its seedlings possessed abundant root hairs with peculiar morphology (swollen terminal parts) and anatomy (spirally formed cell walls) as apparent adaptations for better attachment to the substrate and increase of breaking strain. Later on, their roots became colonized by dark septate mycelium while root hairs were reduced. In adults, most of terminal fine roots possessed the specific fungal association while root hairs were absent. These observations indicate for the first time that processes regulating transition from root hairs to root fungal colonization exist also in some seagrasses. This ontogenetic shift in root traits may suggests an involvement of the specific root symbiosis in the nutrient uptake by the dominant Mediterranean seagrass.

• MeSH
• Alismatales anatomie a histologie   růst a vývoj   mikrobiologie   MeSH
• Ascomycota fyziologie   MeSH
• fyziologická adaptace * MeSH
• kořeny rostlin mikrobiologie   MeSH
• listy rostlin MeSH
• mycelium fyziologie   MeSH
• mykorhiza MeSH
• symbióza * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Středozemní moře MeSH

Natural cytokinins as well as the majority of their synthetic derivatives show negative effects on root growth and development. Changes in morphology, primarily linked to the inhibition of the cell division in the meristematic zone, are manifested as thickening and shortening of the primary root and impaired lateral root branching. Rational design of cytokinin derivatives can partially overcome these drawbacks and reduce the negative effects. Using our database of cytokinin derivatives, we selected several aromatic cytokinin analogs with modifications at the N9 atom of the adenine moiety. We found that tetrahydropyranyl and tetrahydrofuranyl substitutions at the N9 atom led to enhanced acropetal transport of the modified cytokinin, and both derivatives also showed weak anticytokinin activity. Consequently, changes in the distribution of the active cytokinin pool together with gradual metabolic conversion of the modified cytokinin to its free form prevent root growth inhibition that limits cytokinin utilization in micropropagation techniques.

• MeSH
• cytokininy chemie   farmakologie   MeSH
• kořeny rostlin účinky léků   MeSH
• kukuřice setá MeSH
• kultivační techniky * MeSH
• vývoj rostlin účinky léků   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Flax (Linum usitatissimum L.) is an important crop for the production of oil and fiber. In vitro manipulations of flax are used for genetic improvement and breeding while improvements in adventitious root formation are important for biotechnological programs focused on regeneration and vegetative propagation of genetically valuable plant material. Additionally, flax hypocotyl segments possess outstanding morphogenetic capacity, thus providing a useful model for the investigation of flax developmental processes. Here, we investigated the crosstalk between hydrogen peroxide and auxin with respect to reprogramming flax hypocotyl cells for root morphogenetic development. Exogenous auxin induced the robust formation of adventitious roots from flax hypocotyl segments while the addition of hydrogen peroxide further enhanced this process. The levels of endogenous auxin (indole-3-acetic acid; IAA) were positively correlated with increased root formation in response to exogenous auxin (1-Naphthaleneacetic acid; NAA). Histochemical staining of the hypocotyl segments revealed that hydrogen peroxide and peroxidase, but not superoxide, were positively correlated with root formation. Measurements of antioxidant enzyme activities showed that endogenous levels of hydrogen peroxide were controlled by peroxidases during root formation from hypocotyl segments. In conclusion, hydrogen peroxide positively affected flax adventitious root formation by regulating the endogenous auxin levels. Consequently, this agent can be applied to increase flax regeneration capacity for biotechnological purposes such as improved plant rooting.

• MeSH
• antioxidancia metabolismus   MeSH
• biotechnologie MeSH
• hypokotyl účinky léků   růst a vývoj   metabolismus   MeSH
• kořeny rostlin účinky léků   růst a vývoj   metabolismus   MeSH
• kyseliny indoloctové metabolismus   MeSH
• kyseliny naftalenoctové farmakologie   MeSH
• len účinky léků   růst a vývoj   metabolismus   MeSH
• peroxid vodíku metabolismus   farmakologie   MeSH
• přeprogramování buněk účinky léků   MeSH
• regulátory růstu rostlin metabolismus   farmakologie   MeSH
• Publikační typ
• časopisecké články MeSH