The Experts below are selected from a list of 168 Experts worldwide ranked by ideXlab platform
Lien Bosmans - One of the best experts on this subject based on the ideXlab platform.
-
Rhizogenic agrobacteria in hydroponic crops: epidemics, diagnostics and control
Plant Pathology, 2017Co-Authors: Lien Bosmans, Rob Moerkens, Lieve Wittemans, Hans Rediers, Bart LievensAbstract:Rhizogenic Agrobacterium biovar 1, harbouring an Ri-plasmid (Root-inducing plasmid), is the causative agent of Hairy Root Disease (HRD) in the hydroponic cultivation of tomato, cucumber and aubergine. The Disease is characterized by extensive Root proliferation leading to strong vegetative growth and, in severe cases, substantial losses in marketable yield. Agrobacterium biovar 1 is a heterogeneous group of agrobacteria and includes at least 10 genomospecies, among which at least four (G1, G3, G8 and G9) have been associated with HRD in hydroponically grown vegetables. This review has synthesized the current knowledge on rhizogenic Agrobacterium biovar 1, including infection process, current taxonomic status, genetic and phenotypic diversity, detection methods and strategies for Disease control. With regard to the latter, symptom reduction and prevention of infection through cultivation methods and chemical disinfection (e.g. by the use of chlorine-based disinfectants and hydrogen peroxide) are discussed and biocontrol strategies are elaborated on. Recent research has led to the identification of a phylogenetically related clade of Paenibacillus strains that have antagonistic activity against rhizogenic Agrobacterium biovar 1 strains, holding great potential for HRD control. Finally, possible directions for future research are proposed.
-
potential for biocontrol of Hairy Root Disease by a paenibacillus clade
Frontiers in Microbiology, 2017Co-Authors: Lien Bosmans, Irene De Bruijn, Saskia Gerards, Rob Moerkens, Lore Van Looveren, Lieve Wittemans, Bart Van Calenberge, Anneleen Paeleman, Stefan Van Kerckhove, Jef RozenskiAbstract:Rhizogenic Agrobacterium biovar 1 is the causative agent of Hairy Root Disease (HRD) in the hydroponic cultivation of tomato and cucumber causing significant losses in marketable yield. In order to prevent and control the Disease chemical disinfectants such as hydrogen peroxide or hypochlorite are generally applied to sanitize the hydroponic system and/or hydroponic solution. However, effective control of HRD sometimes requires high disinfectant doses that may have phytotoxic effects. Moreover, several of these chemicals may be converted to unwanted by-products with human health hazards. Here we explored the potential of beneficial bacteria as a sustainable means to control HRD. A large collection of diverse bacterial genera was screened for antagonistic activity against rhizogenic Agrobacterium biovar 1 using the agar overlay assay. Out of more than 150 strains tested, only closely related Paenibacillus strains belonging to a particular clade showed antagonistic activity, representing the species P. illinoisensis, P. pabuli, P. taichungensis, P. tundrae, P. tylopili, P. xylanexedens and P. xylanilyticus. Assessment of the spectrum of activity revealed that some strains were able to inhibit the growth of all 35 rhizogenic agrobacteria strains tested, while others were only active against part of the collection, suggesting a different mode of action. Preliminary characterization of the compounds involved in the antagonistic activity of two closely related Paenibacillus strains, tentatively identified as P. xylanexedens, revealed that they are water-soluble and have low molecular weight. Application of a combination of these strains in greenhouse conditions resulted in a significant reduction of HRD, indicating the great potential of these strains to control HRD.
-
efficacy of hydrogen peroxide treatment for control of Hairy Root Disease caused by rhizogenic agrobacteria
Journal of Applied Microbiology, 2016Co-Authors: Lien Bosmans, Rob Moerkens, Lieve Wittemans, Anneleen Paeleman, B Van Calenberge, S Van Kerckhove, Bart Lievens, Hans RediersAbstract:AIMS: Rhizogenic Agrobacterium strains are the causative agent of Hairy Root Disease (HRD), an increasing problem in the hydroponic cultivation of tomato and cucumber in Europe. A previous study has demonstrated that different lineages of rhizogenic agrobacteria are able to form biofilms. Although hydrogen peroxide (H2 O2 ) is a frequently used biocide in hydroponic systems, until now its effectiveness to remove rhizogenic agrobacteria has not been unequivocally demonstrated. Therefore, the main objective of this study was to assess the efficacy of H2 O2 in controlling Agrobacterium-containing biofilms. METHODS AND RESULTS: Using lab-scale experiments, we found a huge variation between different rhizogenic Agrobacterium strains in EC50 values, ranging from 18·8 to 600 ppm H2 O2 , representing the lowest and highest concentration tested respectively. Using pilot-scale experiments in which different H2 O2 concentrations were tested, treatment with 25 ppm H2 O2 was found to be ineffective. In contrast, treatment with 50 ppm significantly affected a catalase-negative Agrobacterium population, while a catalase-positive population was only marginally affected. For the catalase-positive Agrobacterium population, a treatment of 100 ppm H2 O2 was required to be effective. Finally, H2 O2 treatment of HRD in two commercial greenhouses was monitored, and showed that the H2 O2 concentration decreased considerably towards the end of the irrigation circuits. Further, a clear correlation was found between the actual concentration of H2 O2 and the incidence of HRD. CONCLUSION: We showed that H2 O2 may be effective to reduce biofilm formation by rhizogenic bacteria. Nevertheless, it was clear from our results that the required H2 O2 concentration depends on the particular Agrobacterium strain(s) present in the greenhouse. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study that examined the effectiveness of H2 O2 to control HRD in hydroponic systems, and the effect of catalase activity on H2 O2 effectiveness. Our study has direct relevance for the highly intensive horticultural sector.
Olof Olsson - One of the best experts on this subject based on the ideXlab platform.
-
The Agrobacterium rhizogenes rolB and rolC promoters are expressed in pericycle cells competent to serve as Root initials in transgenic hybrid aspen
Physiologia Plantarum, 1997Co-Authors: Ove Nilsson, Hannele Tuominen, Björn Sundberg, Olof OlssonAbstract:Expression of the Agrobacterium rhizogenes rolB and rolC promoters was studied in transgenic hybrid aspen (Populus tremula L. x P. tremuloides Michx.) lines containing a chimeric fusion of either the rolB or the rolC promoter and the reporter gene uidA. The resultant GUS activity was monitored by histochemical analysis in aerial tissues as well as in developing Roots. Both the rolC and rolB promoters were shown to be expressed in the phloem and in the Root tips, which is similar to the expression pattern previously described for annual plants. However, a strong expression of the rolB promoter in the rays of the phloem and the cambial zone of the stem, and of the rolC promoter in groups of pericycle cells prior to and during lateral Root initiation was unique for hybrid aspen. In both stem and Root tissues, the expression of the rolB and rolC promoters was localised primarily in a subset of cells competent to form adventitious or lateral Roots, suggesting that these cells might serve as the target for A. rhizogenes infection. The biological significance of the cell-specific rol gene expression in establishing the Hairy Root Disease is discussed.
-
Getting to the Root: The role of the Agrobacterium rhizogenes rol genes in the formation of Hairy Roots
Physiologia Plantarum, 1997Co-Authors: Ove Nilsson, Olof OlssonAbstract:Agrobacterium tumefaciens and A. rhizogenes are the causative agents of the crown gall and Hairy Root Diseases, respectively. The pathogenicity of both species is caused by an inter-kingdom transfer of DNA from the bacteria to wounded plant cells. This ‘transfer-DNA’ (T-DNA) contains oncogenes whose expression transforms the plant recipient cell into a rapidly dividing tumour cell. In the case of A. tumefaciens, three of these oncogenes have been shown to encode enzymes catalyzing the biosynthesis of the plant growth hormones auxin and cytokinin. Therefore, the unorganized cell division in the crown gall tumour can be largely explained by an unregulated overproduction of these plant growth regulators. In contrast, the Hairy Root Disease is characterized by a massive growth of adventitious Roots at the site of infection. Because of the similarities of the infection processes, and because A. rhizogenes and A. tumefaciens are very closely related, it has been suggested that the most important A. rhizogenes oncogenes, the so called rol genes, are also encoding proteins involved in the regulation of plant hormone metabolism. However, recent data indicate that this is not the case. Thus the rol genes have functions that most likely are different from producing mere alterations of plant hormone concentrations. This review summarizes recent results concerning the expression and function of the rol genes, and presents a model for the role of these genes, especially rolB and rolC, in the A. rhizogenes infection process.
-
Indole-3-acetic acid homeostasis in transgenic tobacco plants expressing the Agrobacterium rhizogenes rolB gene
Plant Journal, 1993Co-Authors: Ove Nilsson, Thomas Schmülling, Alan Crozier, Göran Sandberg, Olof OlssonAbstract:Summary The rolB gene of the plant pathogen Agrobacterium rhizogenes has an important role in the establishment of Hairy Root Disease in infected plant tissues. When expressed as a single gene in transgenic plants the RolB protein gives rise to effects indicative of increased auxin activity. It has been reported that the RolB product is a β-glucosidase and proposed that the physiological and developmental alterations in transgenic plants expressing the rolB gene are the result of this enzyme hydrolysing bound auxins, in particular (indole-3-acetyl)-β-D-glucoside (IAGluc), and thereby bringing about an increase in the intracellular concentration of indole-3-acetic acid (IAA). Using tobacco plants as a test system, this proposal has been investigated in detail. Comparisons have been made between the RolB phenotype and that of IaaM/iaaH transformed plants overproducing IAA. In addition, the levels of IAA and IAA amide and IAA ester conjugates were determined in wild-type and transgenic 35S-rolB tobacco plants and metabolic studies were carried out with [13C6]IAA [2′-14C]IAA, [14C]IAGluc, [5-3H]-2-o-(indole-3-acetyl)-myo-inositol and [14C]indole-3-acetylaspartic acid. The data obtained demonstrate that expression of the rolB encoded protein in transgenic tobacco does not produce a phenotype that resembles that of IAA over producing plants, does not alter the size of the free IAA pool, has no significant effect on the rate of IAA metabolism, and, by implication, appears not to influence the overall rate of IAA biosynthesis. Furthermore, the in vivo hydrolysis of IAGluc, and that of the other IAA conjugates that were tested, is not affected. On the basis of these findings, it is concluded that the RolB phenotype is not the consequence of an increase in the size of the free IAA pool mediated by an enhanced rate of hydrolysis of IAA conjugates.
Ashok K Srivastava - One of the best experts on this subject based on the ideXlab platform.
-
Hairy Root culture for mass production of high value secondary metabolites
Critical Reviews in Biotechnology, 2007Co-Authors: Smita Srivastava, Ashok K SrivastavaAbstract:ABSTRACTPlant cell cultivations are being considered as an alternative to agricultural processes for producing valuable phytochemicals. Since many of these products (secondary metabolites) are obtained by direct extraction from plants grown in natural habitat, several factors can alter their yield. The use of plant cell cultures has overcome several inconveniences for the production of these secondary metabolites. Organized cultures, and especially Root cultures, can make a significant contribution in the production of secondary metabolites. Most of the research efforts that use differentiated cultures instead of cell suspension cultures have focused on transformed (Hairy) Roots. Agrobacterium rhizogenes causes Hairy Root Disease in plants. The neoplastic (cancerous) Roots produced by A. rhizogenes infection are characterized by high growth rate, genetic stability and growth in hormone free media. These genetically transformed Root cultures can produce levels of secondary metabolites comparable to that of...
Ramesh Chandra - One of the best experts on this subject based on the ideXlab platform.
-
Engineering secondary metabolite production in Hairy Roots
Phytochemistry Reviews, 2011Co-Authors: Sheela Chandra, Ramesh ChandraAbstract:Plants are a rich source of valuable secondary metabolites. Plant cell culture technologies developed in the past as possible tools for secondary metabolites production. In most cases, for the large scale production of these compounds, production is too low for commercialization. The cultured cell suspensions being undifferentiated have not gained momentum because of their instability and non-uniformity of the product formation. Secondary metabolite production is under strict metabolic regulation and tissue specific localization. Hence the differentiated cultures such as Hairy Root cultures are widely studied. Agrobacterium rhizogenes causes Hairy Root Disease in plants. Transformed Roots produced by A. rhizogenes infection are characterized by high growth rate, genetic stability and growth in hormone free media. These genetically transformed Root cultures can produce amounts of secondary metabolites comparable to that of intact plants. Elicitation of Hairy Roots leads to increased production of secondary metabolites and also helps in designing of metabolic traps to allow adsorption of product, preventing feedback inhibition and protection of metabolites from degradation in the culture media. Permeabilization and in situ product adsorption result in many fold increase in product yield. T- DNA activation tagging allows overexpressing the respective gene and increasing the product formation in transformed Hairy Roots. Recent progress in transgenic research has opened up the possibility of the metabolic engineering of biosynthetic pathways to produce high-value secondary metabolites. Metabolic engineering offers promising perspectives to improve yields; however it requires the understanding of the regulation of the secondary metabolite pathways involved in the regulation of levels of product, enzymes and genes, including aspects as transport and compartmentation. This article reviews the recent advances in secondary metabolites production in transformed Hairy Roots.
Rob Moerkens - One of the best experts on this subject based on the ideXlab platform.
-
Rhizogenic agrobacteria in hydroponic crops: epidemics, diagnostics and control
Plant Pathology, 2017Co-Authors: Lien Bosmans, Rob Moerkens, Lieve Wittemans, Hans Rediers, Bart LievensAbstract:Rhizogenic Agrobacterium biovar 1, harbouring an Ri-plasmid (Root-inducing plasmid), is the causative agent of Hairy Root Disease (HRD) in the hydroponic cultivation of tomato, cucumber and aubergine. The Disease is characterized by extensive Root proliferation leading to strong vegetative growth and, in severe cases, substantial losses in marketable yield. Agrobacterium biovar 1 is a heterogeneous group of agrobacteria and includes at least 10 genomospecies, among which at least four (G1, G3, G8 and G9) have been associated with HRD in hydroponically grown vegetables. This review has synthesized the current knowledge on rhizogenic Agrobacterium biovar 1, including infection process, current taxonomic status, genetic and phenotypic diversity, detection methods and strategies for Disease control. With regard to the latter, symptom reduction and prevention of infection through cultivation methods and chemical disinfection (e.g. by the use of chlorine-based disinfectants and hydrogen peroxide) are discussed and biocontrol strategies are elaborated on. Recent research has led to the identification of a phylogenetically related clade of Paenibacillus strains that have antagonistic activity against rhizogenic Agrobacterium biovar 1 strains, holding great potential for HRD control. Finally, possible directions for future research are proposed.
-
potential for biocontrol of Hairy Root Disease by a paenibacillus clade
Frontiers in Microbiology, 2017Co-Authors: Lien Bosmans, Irene De Bruijn, Saskia Gerards, Rob Moerkens, Lore Van Looveren, Lieve Wittemans, Bart Van Calenberge, Anneleen Paeleman, Stefan Van Kerckhove, Jef RozenskiAbstract:Rhizogenic Agrobacterium biovar 1 is the causative agent of Hairy Root Disease (HRD) in the hydroponic cultivation of tomato and cucumber causing significant losses in marketable yield. In order to prevent and control the Disease chemical disinfectants such as hydrogen peroxide or hypochlorite are generally applied to sanitize the hydroponic system and/or hydroponic solution. However, effective control of HRD sometimes requires high disinfectant doses that may have phytotoxic effects. Moreover, several of these chemicals may be converted to unwanted by-products with human health hazards. Here we explored the potential of beneficial bacteria as a sustainable means to control HRD. A large collection of diverse bacterial genera was screened for antagonistic activity against rhizogenic Agrobacterium biovar 1 using the agar overlay assay. Out of more than 150 strains tested, only closely related Paenibacillus strains belonging to a particular clade showed antagonistic activity, representing the species P. illinoisensis, P. pabuli, P. taichungensis, P. tundrae, P. tylopili, P. xylanexedens and P. xylanilyticus. Assessment of the spectrum of activity revealed that some strains were able to inhibit the growth of all 35 rhizogenic agrobacteria strains tested, while others were only active against part of the collection, suggesting a different mode of action. Preliminary characterization of the compounds involved in the antagonistic activity of two closely related Paenibacillus strains, tentatively identified as P. xylanexedens, revealed that they are water-soluble and have low molecular weight. Application of a combination of these strains in greenhouse conditions resulted in a significant reduction of HRD, indicating the great potential of these strains to control HRD.
-
efficacy of hydrogen peroxide treatment for control of Hairy Root Disease caused by rhizogenic agrobacteria
Journal of Applied Microbiology, 2016Co-Authors: Lien Bosmans, Rob Moerkens, Lieve Wittemans, Anneleen Paeleman, B Van Calenberge, S Van Kerckhove, Bart Lievens, Hans RediersAbstract:AIMS: Rhizogenic Agrobacterium strains are the causative agent of Hairy Root Disease (HRD), an increasing problem in the hydroponic cultivation of tomato and cucumber in Europe. A previous study has demonstrated that different lineages of rhizogenic agrobacteria are able to form biofilms. Although hydrogen peroxide (H2 O2 ) is a frequently used biocide in hydroponic systems, until now its effectiveness to remove rhizogenic agrobacteria has not been unequivocally demonstrated. Therefore, the main objective of this study was to assess the efficacy of H2 O2 in controlling Agrobacterium-containing biofilms. METHODS AND RESULTS: Using lab-scale experiments, we found a huge variation between different rhizogenic Agrobacterium strains in EC50 values, ranging from 18·8 to 600 ppm H2 O2 , representing the lowest and highest concentration tested respectively. Using pilot-scale experiments in which different H2 O2 concentrations were tested, treatment with 25 ppm H2 O2 was found to be ineffective. In contrast, treatment with 50 ppm significantly affected a catalase-negative Agrobacterium population, while a catalase-positive population was only marginally affected. For the catalase-positive Agrobacterium population, a treatment of 100 ppm H2 O2 was required to be effective. Finally, H2 O2 treatment of HRD in two commercial greenhouses was monitored, and showed that the H2 O2 concentration decreased considerably towards the end of the irrigation circuits. Further, a clear correlation was found between the actual concentration of H2 O2 and the incidence of HRD. CONCLUSION: We showed that H2 O2 may be effective to reduce biofilm formation by rhizogenic bacteria. Nevertheless, it was clear from our results that the required H2 O2 concentration depends on the particular Agrobacterium strain(s) present in the greenhouse. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study that examined the effectiveness of H2 O2 to control HRD in hydroponic systems, and the effect of catalase activity on H2 O2 effectiveness. Our study has direct relevance for the highly intensive horticultural sector.
