Root development
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Strigolactones are the most recently recognized class of phytohormones, which are also known to establish plant symbiosis with arbuscular mycorhizal fungi or induce germination of parasitic plants. Their relatively complex structures and low stability urgently calls for simple derivatives with maintained biological function. We have prepared a series of triazolide strigolactone mimics and studied their ability to affect root development of Arabidopsis thaliana. The strigolactone mimics significantly induced root elongation and lateral root formation while resembling the effect of the reference compound GR24.
- MeSH
- Arabidopsis chemie účinky léků MeSH
- klíčení účinky léků MeSH
- kořeny rostlin chemie účinky léků růst a vývoj MeSH
- laktony chemie farmakologie MeSH
- molekulární struktura MeSH
- regulátory růstu rostlin chemie farmakologie fyziologie MeSH
- symbióza účinky léků 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
Cytokinins are required for symbiotic nodule development in legumes, and cytokinin signaling responses occur locally in nodule primordia and in developing nodules. Here, we show that the Lotus japonicus Ckx3 cytokinin oxidase/dehydrogenase gene is induced by Nod factor during the early phase of nodule initiation. At the cellular level, pCkx3::YFP reporter-gene studies revealed that the Ckx3 promoter is active during the first cortical cell divisions of the nodule primordium and in growing nodules. Cytokinin measurements in ckx3 mutants confirmed that CKX3 activity negatively regulates root cytokinin levels. Particularly, tZ and DHZ type cytokinins in both inoculated and uninoculated roots were elevated in ckx3 mutants, suggesting that these are targets for degradation by the CKX3 cytokinin oxidase/dehydrogenase. The effect of CKX3 on the positive and negative roles of cytokinin in nodule development, infection and regulation was further clarified using ckx3 insertion mutants. Phenotypic analysis indicated that ckx3 mutants have reduced nodulation, infection thread formation and root growth. We also identify a role for cytokinin in regulating nodulation and nitrogen fixation in response to nitrate as ckx3 phenotypes are exaggerated at increased nitrate levels. Together, these findings show that cytokinin accumulation is tightly regulated during nodulation in order to balance the requirement for cell divisions with negative regulatory effects of cytokinin on infection events and root development.
- MeSH
- alely MeSH
- buněčná diferenciace MeSH
- cytokininy metabolismus MeSH
- dusičnany metabolismus MeSH
- fenotyp MeSH
- fixace dusíku genetika MeSH
- fylogeneze MeSH
- homeostáza * MeSH
- kořenové hlízky rostlin genetika růst a vývoj MeSH
- Lotus enzymologie genetika růst a vývoj MeSH
- meristém cytologie růst a vývoj MeSH
- mutace genetika MeSH
- oxidoreduktasy genetika metabolismus MeSH
- promotorové oblasti (genetika) MeSH
- rostlinné geny MeSH
- rostlinné proteiny genetika metabolismus MeSH
- tvorba kořenových hlízek genetika MeSH
- Publikační typ
- časopisecké články MeSH
- 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.
As non-photosynthesizing organs, roots are dependent on diffusion of oxygen from the external environment and, in some instances, from the shoot for their aerobic metabolism. Establishment of hypoxic niches in the developing tissues of plants has been postulated as a consequence of insufficient diffusion of oxygen to satisfy the demands throughout development. Here, we report that such niches are established at specific stages of lateral root primordia development in Arabidopsis thaliana grown under aerobic conditions. Using gain- and loss-of-function mutants, we show that ERF-VII transcription factors, which mediate hypoxic responses, control root architecture by acting in cells with a high level of auxin signaling. ERF-VIIs repress the expression of the auxin-induced genes LBD16, LBD18, and PUCHI, which are essential for lateral root development, by binding to their promoters. Our results support a model in which the establishment of hypoxic niches in the developing lateral root primordia contributes to the shutting down of key auxin-induced genes and regulates the production of lateral roots.
- MeSH
- Arabidopsis cytologie genetika metabolismus MeSH
- hypoxie buňky MeSH
- kořeny rostlin cytologie MeSH
- kyseliny indoloctové metabolismus MeSH
- proteiny huseníčku metabolismus MeSH
- regulace genové exprese u rostlin MeSH
- signální transdukce * 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
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.
