root development
Dotaz
Zobrazit nápovědu
Správný vývoj kořene a ukotvení zubu do kosti jsou důležité pro ustanovení dynamických funkcí tohoto komplexu. Znalosti získané studiem formování zubu, periodoncia a kosti jsou významné také v oblasti regenerativní stomatologie u technik využívajících autotransplantace či kmenové buňky v rámci tkáňového inženýrství. V tommto příspěvku jsou prezentovány nové poznatky získané studiem myších modelů a zároveň diskutovány možné extrapolace na lidskou dentici.
Proper root development and anchorage of the tooth in the bone are essential for dynamic functions of such complex. The knowledge about tooth-periodontium-bone formation becomes essential also for restorative dentistry using autotransplantation techniques or stem cell based tissue engineering. In this contribution, novel findings from the mouse model are presented and related implications for human dentition discussed.
- MeSH
- cementogeneze fyziologie MeSH
- dentinogenesis fyziologie MeSH
- mandibula anatomie a histologie embryologie růst a vývoj MeSH
- modely u zvířat * MeSH
- moláry anatomie a histologie embryologie růst a vývoj MeSH
- myši MeSH
- odontogeneze fyziologie MeSH
- zubní kořen * anatomie a histologie embryologie růst a vývoj MeSH
- Check Tag
- myši MeSH
- Publikační typ
- práce podpořená grantem 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.
BACKGROUND AND AIMS: The maize lrt1 (lateral rootless1) mutant is impaired in its development of lateral roots during early post-embryonic development. The aim of this study was to characterize, in detail, the influences that the mutation exerts on lateral root initiation and the subsequent developments, as well as to describe the behaviour of the entire plant under variable environmental conditions. METHODS: Mutant lrt1 plants were cultivated under different conditions of hydroponics, and in between sheets of moist paper. Cleared whole mounts and anatomical sections were used in combination with both selected staining procedures and histochemical tests to follow root development. Root surface permeability tests and the biochemical quantification of lignin were performed to complement the structural data. KEY RESULTS: The data presented suggest a redefinition of lrt1 function in lateral roots as a promoter of later development; however, neither the complete absence of lateral roots nor the frequency of their initiation is linked to lrt1 function. The developmental effects of lrt1 are under strong environmental influences. Mutant primordia are affected in structure, growth and emergence; and the majority of primordia terminate their growth during this last step, or shortly thereafter. The lateral roots are impaired in the maintenance of the root apical meristem. The primary root shows disturbances in the organization of both epidermal and subepidermal layers. The lrt1-related cell-wall modifications include: lignification in peripheral layers, the deposition of polyphenolic substances and a higher activity of peroxidase. CONCLUSIONS: The present study provides novel insights into the function of the lrt1 gene in root system development. The lrt1 gene participates in the spatial distribution of initiation, but not in its frequency. Later, the development of lateral roots is strongly affected. The effect of the lrt1 mutation is not as obvious in the primary root, with no influences observed on the root apical meristem structure and maintenance; however, development of the epidermis and cortex are impaired.
- MeSH
- buněčná stěna metabolismus MeSH
- epidermis rostlin anatomie a histologie genetika růst a vývoj MeSH
- hydroponie MeSH
- kořeny rostlin cytologie genetika růst a vývoj MeSH
- kukuřice setá cytologie genetika růst a vývoj MeSH
- lignin metabolismus MeSH
- meristém cytologie genetika růst a vývoj MeSH
- mutace MeSH
- polyfenoly metabolismus MeSH
- regulace genové exprese u rostlin * MeSH
- rostlinné proteiny genetika metabolismus MeSH
- semenáček cytologie genetika růst a vývoj MeSH
- výhonky rostlin cytologie genetika růst a vývoj MeSH
- vývojová regulace genové exprese MeSH
- životní prostředí MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Background and Aims: The actin cytoskeleton forms a dynamic network in plant cells. A single-point mutation in the DER1 (deformed root hairs1) locus located in the sequence of ACTIN2, a gene for major actin in vegetative tissues of Arabidopsis thaliana, leads to impaired root hair development (Ringli C, Baumberger N, Diet A, Frey B, Keller B. 2002. ACTIN2 is essential for bulge site selection and tip growth during root hair development of Arabidopsis. Plant Physiology129: 1464-1472). Only root hair phenotypes have been described so far in der1 mutants, but here we demonstrate obvious aberrations in the organization of the actin cytoskeleton and overall plant development. Methods: Organization of the actin cytoskeleton in epidermal cells of cotyledons, hypocotyls and roots was studied qualitatively and quantitatively by live-cell imaging of transgenic lines carrying the GFP-FABD2 fusion protein and in fixed cells after phalloidin labelling. Patterns of root growth were characterized by FM4-64 vital staining, light-sheet microscopy imaging and microtubule immunolabelling. Plant phenotyping included analyses of germination, root growth and plant biomass. Key Results: Speed of germination, plant fresh weight and total leaf area were significantly reduced in the der1-3 mutant in comparison with the C24 wild-type. Actin filaments in root, hypocotyl and cotyledon epidermal cells of the der1-3 mutant were shorter, thinner and arranged in more random orientations, while actin bundles were shorter and had altered orientations. The wavy pattern of root growth in der1-3 mutant was connected with higher frequencies of shifted cell division planes (CDPs) in root cells, which was consistent with the shifted positioning of microtubule-based preprophase bands and phragmoplasts. The organization of cortical microtubules in the root cells of the der1-3 mutant, however, was not altered. Conclusions: Root growth rate of the der1-3 mutant is not reduced, but changes in the actin cytoskeleton organization can induce a wavy root growth pattern through deregulation of CDP orientation. The results suggest that the der1-3 mutation in the ACT2 gene does not influence solely root hair formation process, but also has more general effects on the actin cytoskeleton, plant growth and development.
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
Ethylene is an important phytohormone for plant adaptation to heavy metal stress. However, the effects of ethylene on radial apoplastic transport of Cd remain elusive. This study investigated the role of ethylene on apoplastic barriers development and consequences for Cd uptake in Sedum alfredii. In response to Cd, endogenous ethylene production in hyperaccumulating ecotype (HE) roots was decreased due to the down-regulated expressions of ethylene biosynthesis genes, while the opposite result was observed in non-hyperaccumulating ecotype (NHE). Interestingly, the ethylene emission in HE was always higher than that in NHE, regardless of Cd concentrations. Results of exogenous application of ethylene biosynthesis precursor/inhibitor indicate that ethylene with high level would delay the formation of apoplastic barriers in HE through restraining phenylalanine ammonia lyase activity and gene expressions related to lignin/suberin biosynthesis. Simultaneously, correlation analyses suggest that Cd-induced apoplastic barriers formation may be also regulated by ethylene signaling. By using an apoplastic bypass tracer and scanning ion-selected electrode, we observed that the delayed deposition of apoplastic barriers significantly promoted Cd influx in roots. Taken together, high endogenous ethylene in HE postponed the formation of apoplastic barriers and thus promoted the Cd accumulation in the apoplast of roots.
Vitamin B(6) (pyridoxal 5'-phosphate) is an essential cofactor of many metabolic enzymes. Plants biosynthesize the vitamin de novo employing two enzymes, pyridoxine synthase1 (PDX1) and PDX2. In Arabidopsis (Arabidopsis thaliana), there are two catalytically active paralogs of PDX1 (PDX1.1 and PDX1.3) producing the vitamin at comparable rates. Since single mutants are viable but the pdx1.1 pdx1.3 double mutant is lethal, the corresponding enzymes seem redundant. However, the single mutants exhibit substantial phenotypic differences, particularly at the level of root development, with pdx1.3 being more impaired than pdx1.1. Here, we investigate the differential regulation of PDX1.1 and PDX1.3 by identifying factors involved in their disparate phenotypes. Swapped-promoter experiments clarify the presence of distinct regulatory elements in the upstream regions of both genes. Exogenous sucrose (Suc) triggers impaired ethylene production in both mutants but is more severe in pdx1.3 than in pdx1.1. Interestingly, Suc specifically represses PDX1.1 expression, accounting for the stronger vitamin B6 deficit in pdx1.3 compared with pdx1.1. Surprisingly, Suc enhances auxin levels in pdx1.1, whereas the levels are diminished in pdx1.3. In the case of pdx1.3, the previously reported reduced meristem activity combined with the impaired ethylene and auxin levels manifest the specific root developmental defects. Moreover, it is the deficit in ethylene production and/or signaling that triggers this outcome. On the other hand, we hypothesize that it is the increased auxin content of pdx1.1 that is responsible for the root developmental defects observed therein. We conclude that PDX1.1 and PDX1.3 play partially nonredundant roles and are differentially regulated as manifested in disparate root growth impairment morphologies.
- MeSH
- Arabidopsis růst a vývoj metabolismus fyziologie MeSH
- fenotyp MeSH
- homeostáza fyziologie MeSH
- kořeny rostlin růst a vývoj MeSH
- kyseliny indoloctové metabolismus MeSH
- proteiny huseníčku metabolismus fyziologie MeSH
- regulátory růstu rostlin metabolismus fyziologie MeSH
- transferasy dusíkatých skupin metabolismus fyziologie MeSH
- vitamin B6 biosyntéza fyziologie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The apical hook is a transiently formed structure that plays a protective role when the germinating seedling penetrates through the soil towards the surface. Crucial for proper bending is the local auxin maxima, which defines the concave (inner) side of the hook curvature. As no sign of asymmetric auxin distribution has been reported in embryonic hypocotyls prior to hook formation, the question of how auxin asymmetry is established in the early phases of seedling germination remains largely unanswered. Here, we analyzed the auxin distribution and expression of PIN auxin efflux carriers from early phases of germination, and show that bending of the root in response to gravity is the crucial initial cue that governs the hypocotyl bending required for apical hook formation. Importantly, polar auxin transport machinery is established gradually after germination starts as a result of tight root-hypocotyl interaction and a proper balance between abscisic acid and gibberellins.This article has an associated 'The people behind the papers' interview.
- MeSH
- Arabidopsis MeSH
- geneticky modifikované rostliny MeSH
- gibereliny metabolismus MeSH
- hypokotyl růst a vývoj MeSH
- klíčení fyziologie MeSH
- kořeny rostlin růst a vývoj MeSH
- kyselina abscisová metabolismus MeSH
- kyseliny indoloctové metabolismus MeSH
- meristém růst a vývoj MeSH
- percepce tíhy fyziologie MeSH
- proteiny huseníčku metabolismus MeSH
- regulace genové exprese u rostlin MeSH
- regulátory růstu rostlin metabolismus MeSH
- semenáček růst a vývoj MeSH
- vývojová regulace genové exprese MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
