scholarly journals Induction of Lateral Root Structure Formation on Petunia Roots: A Novel Effect of GMI1000 Ralstonia solanacearum Infection Impaired in Hrp Mutants

2006 ◽  
Vol 19 (6) ◽  
pp. 597-606 ◽  
Author(s):  
Lena Zolobowska ◽  
Frédérique Van Gijsegem
Keyword(s):  
Ralstonia Solanacearum ◽  
Lateral Root ◽  
Plant Pathogens ◽  
Lateral Roots ◽  
Root Tips ◽  
Whole Plant ◽  
Systemic Spread ◽  
Mutant Strains ◽  
Architecture Development ◽  
Lateral Structures

Ralstonia solanacearum is a soilborne plant pathogen that invades its host via roots. As in many gram-negative bacterial plant pathogens, the R. solanacearum Hrp type III secretion system is essential for interactions of the bacterium with plants; however, the related mechanisms involved in disease expression are largely unknown. In this work, we examined the effects of infection by R. solanacearum GMI1000 and Hrp mutants on the root system of petunia plants. Both the wild-type and mutant strains disturbed the petunia root architecture development by inhibiting lateral root elongation and provoking swelling of the root tips. In addition, GMI100 but not the Hrp mutants induced the formation of new root lateral structures (RLS). This ability is shared by other, but not all, R. solanacearum strains tested. Like lateral roots, these new structures arise from divisions of pericycle founder cells which, nevertheless, exhibit an abnormal morphology. These RLS are efficient colonization sites allowing extensive bacterial multiplication. However, they are not required for the bacterial vascular invasion that leads to the systemic spread of the bacterium through the whole plant, indicating that, instead, they might play a role in the rhizosphere-related stages of the R. solanacearum life cycle.

Temperature Effects on Absorption and Translocation of Trifluralin and Methazole in Peanuts

Weed Science ◽  
1972 ◽  
Vol 20 (4) ◽  
pp. 285-289 ◽  
Author(s):  
K. Hawxby ◽  
E. Basler ◽  
P. W. Santelmann
Keyword(s):  
Temperature Effects ◽  
Lateral Root ◽  
Initial Rate ◽  
Lateral Roots ◽  
Leaf Tissue ◽  
Root Tips ◽  
Plant Parts ◽  
Tap Root ◽  
Rate Of Absorption ◽  
Nutrient Solutions

The absorption and translocation of14C-labeled α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) and 2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione methazole from nutrient solutions of various temperatures by(Arachis hypogaeaL. ‘Starr’) seedlings were determined. The accumulation of trifluralin in roots at 24 hr after exposure to trifluralin was greatest at 21 C and decreased at higher temperatures up to 38 C. The amounts of trifluralin translocated and accumulated in hypocotyls, tops, and cotyledons were small but generally increased with temperature. The initial rate of absorption of trifluralin was greater in excised lateral root tips than in tap root tips, but there was a greater accumulation in excised tap roots at 24 hr. The initial rates of absorption were higher for excised lateral roots at high temperatures. Total absorption of trifluralin at equilibrium was not proportional to the initial rates of absorption but was highest at low (21 C) and high (38 C) temperatures for excised lateral roots. The absorption of methazole by roots and translocation to other plant parts increased linearly with temperature, and it tended to accumulate in the mature leaf tissue.

scholarly journals Expression Studies on AUX1-like Genes in Medicago truncatula Suggest That Auxin Is Required at Two Steps in Early Nodule Development

2001 ◽  
Vol 14 (3) ◽  
pp. 267-277 ◽  
Author(s):  
Françoise de Billy ◽  
Cathy Grosjean ◽  
Sean May ◽  
Malcolm Bennett ◽  
Julie V. Cullimore
Keyword(s):  
Medicago Truncatula ◽  
Lateral Root ◽  
Sequence Similarity ◽  
Lateral Roots ◽  
Peripheral Region ◽  
Nodule Development ◽  
Central Position ◽  
Root Tips ◽  
High Sequence Similarity ◽  
Primary Roots

Medicago truncatula contains a family of at least five genes related to AUX1 of Arabidopsis thaliana (termed MtLAX genes for Medicago truncatula-like AUX1 genes). The high sequence similarity between the encoded proteins and AUX1 implies that the MtLAX genes encode auxin import carriers. The MtLAX genes are expressed in roots and other organs, suggesting that they play pleiotropic roles related to auxin uptake. In primary roots, the MtLAX genes are expressed preferentially in the root tips, particularly in the provascular bundles and root caps. During lateral root and nodule development, the genes are expressed in the primordia, particularly in cells that were probably derived from the pericycle. At slightly later stages, the genes are expressed in the regions of the developing organs where the vasculature arises (central position for lateral roots and peripheral region for nodules). These results are consistent with MtLAX being involved in local auxin transport and suggest that auxin is required at two common stages of lateral root and nodule development: development of the primordia and differentiation of the vasculature.

scholarly journals Xylem Colonization by an HrcV¯ Mutant of Ralstonia solanacearum Is a Key Factor for the Efficient Biological Control of Tomato Bacterial Wilt

1998 ◽  
Vol 11 (9) ◽  
pp. 869-877 ◽  
Author(s):  
Christophe Etchebar ◽  
Danièle Trigalet-Demery ◽  
Frédérique van Gijsegem ◽  
Jacques Vasse ◽  
André Trigalet
Keyword(s):  
Mutant Strain ◽  
Ralstonia Solanacearum ◽  
Lateral Root ◽  
Pathogenic Strain ◽  
Staining Procedure ◽  
Bacterial Suspension ◽  
Marker Genes ◽  
Wild Type ◽  
Root Tips ◽  
Challenge Inoculation

Microscopic studies of the colonization of the vascular tissues of tomato by an HrcV¯ (formerly HrpO¯) mutant strain of Ralstonia solanacearum were carried out after either root inoculation of the mutant strain alone or delayed challenge inoculation by a pathogenic strain. The use of two different marker genes, lacZ and uidA, introduced into either mutant or wild-type strains, respectively, permitted histological observation for the presence of both strains simultaneously. In roots, both strains could be found together in infected root tips and in lateral root emergence sites (lateral root cracks), but these bacterial strains subsequently invaded separate xylem vessels in the root system. At the hypocotyl level, a novel staining procedure, in conjunction with bacterial isolation and counting, showed three vascular colonization patterns: exclusive colonization by each of the competitors or simultaneous presence of each strain in separate xylem vessels. The relative frequencies of these patterns depended upon the root inoculation techniques used. The presence of one population always influenced the density of the other challenge-inoculated population. In plants inoculated with both wild-type and mutant strains, the population of the wild-type strain is lower than in plants inoculated with the wild type alone. In contrast, growth of the HrcV¯ mutant strain was significantly increased in the presence of the pathogenic strain. Two agriculturally acceptable techniques for plant inoculation were tested. Inoculation of plants by transplanting them into soil amended with clay micro-granules impregnated with the HrcV¯ mutant strain gave higher and more reproducible colonization of the plants than inoculation by watering a bacterial suspension on the roots. Significant percentages of exclusive colonization by the HrcV¯ mutant strain were only obtained after the clay microgranule inoculation technique. Competition for space in xylem vessels is one of the possible explanations for the protective ability of the HrcV¯ mutant strain against subsequent invasion by a pathogenic strain.

Nitrate and glutamate sensing by plant roots

2005 ◽  
Vol 33 (1) ◽  
pp. 283-286 ◽  
Author(s):  
S. Filleur ◽  
P. Walch-Liu ◽  
Y. Gan ◽  
B.G. Forde
Keyword(s):  
Root Growth ◽  
Lateral Root ◽  
Lateral Roots ◽  
Primary Root ◽  
Root Tip ◽  
Root Tips ◽  
Environmental Signals ◽  
Specific Effects ◽  
Large Numbers ◽  
Low Concentrations

The architecture of a root system plays a major role in determining how efficiently a plant can capture water and nutrients from the soil. Growth occurs at the root tips and the process of exploring the soil volume depends on the behaviour of large numbers of individual root tips at different orders of branching. Each root tip is equipped with a battery of sensory mechanisms that enable it to respond to a range of environmental signals, including nutrients, water potential, light, gravity and touch. We have previously identified a MADS (MCM1, agamous, deficiens and SRF) box gene (ANR1) in Arabidopsis thaliana that is involved in modulating the rate of lateral root growth in response to changes in the external NO3− supply. Transgenic plants have been generated in which a constitutively expressed ANR1 protein can be post-translationally activated by treatment with dexamethasone (DEX). When roots of these lines are treated with DEX, lateral root growth is markedly stimulated but there is no effect on primary root growth, suggesting that one or more components of the regulatory pathway that operate in conjunction with ANR1 in lateral roots may be absent in the primary root tip. We have recently observed some very specific effects of low concentrations of glutamate on root growth, resulting in significant changes in root architecture. Experimental evidence suggests that this response involves the sensing of extracellular glutamate by root tip cells. We are currently investigating the possible role of plant ionotropic glutamate receptors in this sensory mechanism.

scholarly journals In vitro ectomycorrhiza formation by monokaryotic and dikaryotic isolates of Pisolithus microcarpus in Eucalyptus grandis

2010 ◽  
Vol 34 (3) ◽  
pp. 377-387 ◽  
Author(s):  
Maurício Dutra Costa ◽  
André Narvaes da Rocha Campos ◽  
Matheus Loureiro Santos ◽  
Arnaldo Chaer Borges
Keyword(s):  
Lateral Root ◽  
Morphological Changes ◽  
Lateral Roots ◽  
Eucalyptus Grandis ◽  
Model Systems ◽  
Root Yield ◽  
Root Tips ◽  
In Vitro Synthesis ◽  
Synthesis Medium

The formation of ectomycorrhizas by monokaryotic and dikaryotic isolates of Pisolithus microcarpus (Cooke & Massee) G. Cunn. in Eucalyptus grandis W. Hill ex Maid. was studied by in vitro synthesis in Petri dishes. The formation of ectomycorrhizas was observed for all strains tested. Ectomycorrhizas formed by the monokaryotic strains presented a sheath of hyphae around the roots and a Hartig net limited to the epidermis layer, typical of the angiosperm ectomycorrhizas. Colonization rates, a measure of the number of ectomycorrhizas in relation to the total number of lateral root tips, varied from 23 to 62%. Some monokaryotic strains stimulated the formation of lateral roots, promoting increases of up to 109% above the control. The presence of some of the isolates in the in vitro synthesis medium stimulated the production of thicker lateral root tips. The dimensions of the lateral roots tips and ectomycorrhizas varied from one isolate to the next, indicating a variation in their capacity to provoke morphological changes in the host plant roots. The dikaryotic strain M5M11 presented higher values for lateral root yield, number of ectomycorrhizas, and colonization percentage than the corresponding monokaryotic strains, M5 and M11. This indicated the possibility of selecting compatible performing monokaryotic isolates for the yield of superior dikaryotic strains. The set of monokaryotic strains tested varied greatly in their ability to colonize E. grandis roots and cause secondary metabolism-related morphological changes in roots, providing a wealth of model systems for the study of genetic, physiological, and morphogenetic processes involved in Pisolithus-Eucalyptus ectomycorrhiza formation.

scholarly journals Role of Ascorbate in the Regulation of the Arabidopsis thaliana Root Growth by Phosphate Availability

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Jarosław Tyburski ◽  
Kamila Dunajska-Ordak ◽  
Monika Skorupa ◽  
Andrzej Tretyn
Keyword(s):  
Root Growth ◽  
Lateral Root ◽  
Root Elongation ◽  
Lateral Roots ◽  
Primary Root ◽  
Root Hairs ◽  
P Availability ◽  
Root Tips ◽  
P Deficiency ◽  
Phosphate Availability

Arabidopsis root system responds to phosphorus (P) deficiency by decreasing primary root elongation and developing abundant lateral roots. Feeding plants with ascorbic acid (ASC) stimulated primary root elongation in seedlings grown under limiting P concentration. However, at high P, ASC inhibited root growth. Seedlings of ascorbate-deficient mutant (vtc1) formed short roots irrespective of P availability. P-starved plants accumulated less ascorbate in primary root tips than those grown under high P. ASC-treatment stimulated cell divisions in root tips of seedlings grown at low P. At high P concentrations ASC decreased the number of mitotic cells in the root tips. The lateral root density in seedlings grown under P deficiency was decreased by ASC treatments. At high P, this parameter was not affected by ASC-supplementation. vtc1 mutant exhibited increased lateral root formation on either, P-deficient or P-sufficient medium. Irrespective of P availability, high ASC concentrations reduced density and growth of root hairs. These results suggest that ascorbate may participate in the regulation of primary root elongation at different phosphate availability via its effect on mitotic activity in the root tips.

scholarly journals Early Growth and Development of Pawpaw [Asimina triloba (L.) Dunal] Seedlings in the Greenhouse as Influenced by Shade and Root-zone Modification

HortScience ◽  
1997 ◽  
Vol 32 (3) ◽  
pp. 532E-533
Author(s):  
Desmond R. Layne ◽  
L.N. Peters
Keyword(s):  
Growth And Development ◽  
Lateral Root ◽  
Root Zone ◽  
Plant Biomass ◽  
Lateral Roots ◽  
Incident Light ◽  
Light Level ◽  
Control Treatment ◽  
Whole Plant ◽  
Split Plot

This experiment was designed to determine the optimal light level for growing pawpaw seedlings in the greenhouse. In addition, we wanted to determine if modifying the root-zone would positively impact pawpaw seedling growth and development. Experimental treatments were imposed from seed sowing until the plants were destructively harvested. The experimental design was a split-plot, where blocking was done by position in the greenhouse. The main plot of the experiment was shade. This was accomplished by growing seedlings under a wooden frame covered with shadecloth to reduce incident light intensity received by the plant by 30%, 55%, 80%, or 95%. The control treatment was 0% shade or ambient greenhouse light level. The split-plot was root-zone modification. Half of all growing containers were untreated (control) while the other half were painted with SpinOut™, a commercially available product used to reduce root spiraling in nursery containers. There were 40 replicate seedlings per experimental treatment combination per block. Seedling shoot length and unfolded leaf number was recorded twice a week from seedling emergence until destructive harvest. Whole-plant leaf area was also determined. Leaves, stems, and tap and lateral roots were separated and dried to determine biomass partitioned to the respective organs. Up to 55% shade did not significantly reduce whole-plant biomass, while plants at 80% and 95% shade were stunted. Shade in the greenhouse is not required as was previously thought. Specific leaf mass and lateral root mass decreased as shade increased. Neither tap or lateral root dry weights were significantly affected by root-zone modification. New recommendations for container production of pawpaws in the greenhouse will be discussed.

Lateral root formation and nutrients: nitrogen in the spotlight

2021 ◽  
Author(s):  
Pierre-Mathieu Pélissier ◽  
Hans Motte ◽  
Tom Beeckman
Keyword(s):  
Signaling Pathways ◽  
Root System ◽  
Root Development ◽  
Lateral Root ◽  
Molecular Mechanisms ◽  
Root Formation ◽  
Lateral Roots ◽  
Nutrient Use Efficiency ◽  
Lateral Root Formation ◽  
Lateral Root Development

Abstract Lateral roots are important to forage for nutrients due to their ability to increase the uptake area of a root system. Hence, it comes as no surprise that lateral root formation is affected by nutrients or nutrient starvation, and as such contributes to the root system plasticity. Understanding the molecular mechanisms regulating root adaptation dynamics towards nutrient availability is useful to optimize plant nutrient use efficiency. There is at present a profound, though still evolving, knowledge on lateral root pathways. Here, we aimed to review the intersection with nutrient signaling pathways to give an update on the regulation of lateral root development by nutrients, with a particular focus on nitrogen. Remarkably, it is for most nutrients not clear how lateral root formation is controlled. Only for nitrogen, one of the most dominant nutrients in the control of lateral root formation, the crosstalk with multiple key signals determining lateral root development is clearly shown. In this update, we first present a general overview of the current knowledge of how nutrients affect lateral root formation, followed by a deeper discussion on how nitrogen signaling pathways act on different lateral root-mediating mechanisms for which multiple recent studies yield insights.

scholarly journals Auxin-Induced SaARF4 Downregulates SaACO4 to Inhibit Lateral Root Formation in Sedum alfredii Hance

2021 ◽  
Vol 22 (3) ◽  
pp. 1297
Author(s):  
Dong Xu ◽  
Zhuchou Lu ◽  
Guirong Qiao ◽  
Wenmin Qiu ◽  
Longhua Wu ◽  
...  
Keyword(s):  
Lateral Root ◽  
Ethylene Biosynthesis ◽  
Luciferase Assay ◽  
Sedum Alfredii ◽  
Ethylene Synthesis ◽  
Root Tips ◽  
Sedum Alfredii Hance ◽  
Auxin Distribution ◽  
Distribution Mode ◽  
High Level

Lateral root (LR) formation promotes plant resistance, whereas high-level ethylene induced by abiotic stress will inhibit LR emergence. Considering that local auxin accumulation is a precondition for LR generation, auxin-induced genes inhibiting ethylene synthesis may thus be important for LR development. Here, we found that auxin response factor 4 (SaARF4) in Sedum alfredii Hance could be induced by auxin. The overexpression of SaARF4 decreased the LR number and reduced the vessel diameters. Meanwhile, the auxin distribution mode was altered in the root tips and PIN expression was also decreased in the overexpressed lines compared with the wild-type (WT) plants. The overexpression of SaARF4 could reduce ethylene synthesis, and thus, the repression of ethylene production decreased the LR number of WT and reduced PIN expression in the roots. Furthermore, the quantitative real-time PCR, chromatin immunoprecipitation sequencing, yeast one-hybrid, and dual-luciferase assay results showed that SaARF4 could bind the promoter of 1-aminocyclopropane-1-carboxylate oxidase 4 (SaACO4), associated with ethylene biosynthesis, and could downregulate its expression. Therefore, we concluded that SaARF4 induced by auxin can inhibit ethylene biosynthesis by repressing SaACO4 expression, and this process may affect auxin transport to delay LR development.

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