Phytopathogenic Bacterium Agrobacterium Tumefaciens Research Articles

Bacillus subtilis SPB1 lipopeptide biosurfactant: antibacterial efficiency against the phytopathogenic bacteria Agrobacterium tumefaciens and compared production in submerged and solid state fermentation systems.

Bacillus subtilis SPB1 derived biosurfactants (BioS) proved its bio-control activity against Agrobacterium tumefaciens using tomato plant. Almost 83% of disease symptoms triggered by Agrobacterium tumefaciens were reduced. Aiming potential application, we studied lipopeptide cost-effective production in both fermentations systems, namely the submerged fermentation (SmF) and the solid-state fermentation (SSF) as well as the use of Aleppo pine waste and confectionery effluent as cheap substrates. Optimization studies using Box-Behnken (BB) design followed by the analysis with response surface methodology were applied. When using an effluent/sea water ratio of 1, Aleppo pine waste of 14.08g/L and an inoculum size of 0.2, a best production yield of 17.16 ± 0.91mg/g was obtained for the SmF. While for the SSF, the best production yield of 27.59 ± 1.63mg/g was achieved when the value of Aleppo pine waste, moisture, and inoculum size were, respectively, equal to 25g, 75%, and 0.2. Hence, this work demonstrated the superiority of SSF over SmF.

СИНТЕЗ ТА АНТИМІКРОБНА АКТИВНІСТЬ КОЛОЇДНИХ РОЗЧИНІВ БІКОМПОНЕНТНИХ НАНОЧАСТИНОК Ag/CuO СТАБІЛІЗОВАНИХ РАМНОЛІПІДОМ

Despite the extremely high activity of researchers in the direction of green synthesis of nano-particles of silver, copper, as well as bimetallic nanoparticles Ag/Cu-NPs, the many aspects of the synthesis of nanoparticles based on silver and copper remain unexplored, in particular, the studies on the influence of the nature of biosurfactants on the characteristics are relevant obtained nano¬particles, in particular their size, shape, etc., as well as the influence of the morphology and compo¬sition of nanoparticles on their antimicrobial properties. Therefore, the purpose of this work was to synthesize colloidal solutions of bicomponent Ag/CuO-NPs nanoparticles of different composition and to investigate their antimicrobial activity. Bicomponent Ag/CuO nanoparticles of different composition were obtained by the method of coprecipitation of Ag+ and Cu2+ cations in solution of rhamnolipid. It was found that the process of formation of monocomponent CuO nanoparticles is completed within 2.5 hours but the reduction of silver ions in aqueous solutions of RL occurs within a few minutes. The obtained Ag/CuO-NPs were studied using UV-visible spectroscopy and the method of powder diffraction of X-rays. It was found that the absorption spectra of Ag/CuO-NPs solutions are characterized by two maxima at 280 and 410 nm, which correspond to the surface plasmon resonance bands of CuO and Ag-NPs, res-pectively. Based on the obtained data, it is reasonable to assume that the obtained Ag/CuO-NPs can form core-shell structures in which the role of the core will be played by silver surrounded by a CuO shell. Taking into account the prospects of using the nanoparticles based on silver and copper as antimicrobial agents for the plant protection, the antimicrobial activity of the synthesized Ag/CuO-NPs was investigated. The gram-negative bacteria-phytopathogens were used as test microorganisms, namely Agrobacterium tumefaciens, which is the causative agent of crown gall disease of a wide range of agricultural crops and Xanthomonas campestris, which is the causative agent of the "black rot" disease in cruciferous vegetables. The antimicrobial activity of the synthesized colloidal solutions of Ag/CuO was evaluated by the minimum inhibitory concentration values. The results of the studies of antimicrobial activity of the synthesized Ag/CuO colloidal solutions showed that the obtained preparations effectively inhibit the growth of phytopathogenic bacteria Agrobacterium tumefaciens and Xanthomonas campestris and it was found that the obtained drugs are more active against the Xanthomonas campestris.

Unusual mixed-valence CuII/CuI coordination polymer based on 2,5-bis(pyridine-2-yl)-1,3,4-thiadiazole and thiocyanate: Synthesis, structural characterization and antimicrobial in vitro activity assessment

The unusual mixed valence CuII/CuI coordination polymer based on 2,5-bis(pyridine-2-yl)-1,3,4-thiadiazole [CuI3CuIIL2(SCN)5]n has been prepared by reaction between the thiadiazole ligand (L), CuCl2·2H2O and KSCN in H2O/CH3CN solution. The title complex has been characterized using single-crystal X-ray diffraction, and spectroscopic measurements, as well as Hirshfeld surface analysis. TGA analysis and magnetic measurements were also performed. The polymeric complex crystallizes in monoclinic symmetry and C2/c space group with three independent copper crystallographic sites, trigonal and tetrahedral for CuI and octahedral for CuII. The thermal analysis reveals that this complex is thermally stable up to 200 °C. Magnetic measurements carried out on [CuI3CuIIL2(SCN)5]n complex indicate a paramagnetic behaviour. While this new polymer exhibited a noticeable activity against the phytopathogenic bacteria Agrobacterium tumefaciens, no significant activity was recorded against Pseudomonas syringae pv. syringae and Pseudomonas syringae pv. tobacco nor against the phytopathogenic fungi Verticillium dahlia and Fusarium oxysporum fsp. melonis.

Antagonistic Activity of Azotobаcter vinelandii IMV B-7076 against Phytopathogenic Microorganisms

Bacteria of the genus Azotobacter are known for their ability to stimulate plant growth and development. Azotobacter vinelandii IMV B-7076 strain was isolated from Zhytomyr region soil of Ukraine. It is one of the components of the "Azogran" complex bacterial preparation for plant growing. It has been established that A. vinelandii IMV B-7076 synthesizes biologically active substances that promote plant development. At the same time, the antagonistic activity of A. vinelandii IMV B-7076 against phytopathogens has not yet been studied, so this became the aim of this work. Methods. The antagonistic activity of A. vinelandii IMV B-7076 was determined by agar well diffusion and agar blocks methods. Results. It was shown that A. vinelandii IMV B-7076 had antagonistic activity against some phytopathogenic fungi. In particular, the diameter of growth inhibition zones of Alternaria alternata 16861, Fusarium avenaceum 50720, Fusarium verticillioides 50463, Fusarium lactis 50719, Fusarium oxysporum 54201, Fusarium poae 50704 was 14-37 mm, Bipolaris sorokiniana 16868 and Fusarium solani – 11-13 mm. Fusarium culmorum 50716 and Fusarium graminearum 50662 were not sensitive to A. vinelandii IMV B-7076 metabolites. Notably, the antagonistic effect was demonstrated in mycelial growth and spore formation inhibition, in fungal mycelium discoloration. It was also demonstrated that A. vinelandii IMV B-7076 did not show antagonistic activity against phytopathogenic bacteria Agrobacterium tumefaciens 8628, Pectobacterium carotovorum subsp. carotovorum 8982, Pseudomonas fluorescens 8573, Pseudomonas syringae pv. syringae 8511, Clavibacter michiganensis subsp. michiganensis 13a, Xanthomonas campestris pv. campestris 8003b. Conclusions. Studied A. vinelandii IMV B-7076 strain is characterized by antagonistic activity against phytopathogenic fungi and does not have antibacterial properties against phytopathogenic bacteria. The antifungal activity of A. vinelandii IMV B-7076, as a component of "Azogran", will be useful for this bacterial preparation application in plant growing.

A new homobimetallic cobalt(II) complex based on the tetradentate 3,5-bis(2-pyridyl)-1H-1,2,4-triazole ligand: Synthesis, crystal structure, Hirshfeld analysis, spectroscopic characterization, magnetic properties and antimicrobial activities

A novel homobimetallic cobalt(II) complex, [Co2(bpt)2(H2O)4](NO3)2·2H2O (bpt = 3,5-bis(2-pyridyl)-1,2,4-triazolate), has been synthesized and characterized by single crystal X-ray diffraction, Hirshfeld surface analysis, as well as UV–Visible and FTIR techniques. The crystal structure determination shows that the dinuclear complex crystallizes in the triclinic crystal system with the P1- space group. The (N′,N1,N2,N″)2 double bridging coordination mode is realised with a distorted octahedral N4O2-coordinated cobalt centre. The structure cohesion is ensured by different intermolecular hydrogen bonds, π–π stacking interactions and intermolecular lone-pair···π interactions. The structure consists of [Co2(bpt)2]2+ dimeric units with a cobalt-cobalt distance of 4.170(2) Å. Magnetic measurements carried out on the homobimetallic complex indicate a relatively weak antiferromagnetic interaction between the two cobalt centres. This complex exhibited antimicrobial activity against several strains of the fungal phytopathogens Verticillium dahliae and Fusarium oxysporum fsp. melonis, as well as against the phytopathogenic bacteria Agrobacterium tumefaciens, suggesting its use in crop protection.

Chemical Composition and in vivo Efficacy of the Essential Oil of Mentha piperita L. in the Suppression of Crown Gall Disease on Tomato Plants.

This study was undertaken to determine the antibacterial efficacy of the essential oil (EO) of peppermint (Mentha piperita L.), in vitro and in vivo, against the phytopathogenic bacteria Agrobacterium tumefaciens (A. tumefaciens). The EO composition of M. piperita L. was investigated by Gas chromatography-mass spectrometry (GC/MS) with 26 identified volatile constituents. The major constituents were menthol (33.59%) and iso-menthone (33.00%). This EO exerted a bactericidal activity against multiple strains of Agrobacterium species with minimum inhibitory concentration (MIC) values ranged from 0.01 to 12.50 mg/mL. In planta experiments, M. piperita EO, tested at concentration of 200 mg/mL, completely inhibited the formation of tumors on tomato plants inoculated with pathogenic strain A. tumefaciens ATCC 23308T. These results suggest that M. piperita EO could be used to control plant bacterial disease caused by A. tumefaciens.

From the tumor-inducing principle to plant biotechnology and its importance for society

This dialogue was held between the Guest Editors of the Special Issue on "Plant Transgenesis" of the Int. J. Dev. Biol. and Marc Van Montagu. Research in the group of Marc Van Montagu and Jeff Schell in the 1970s was essential to reveal how the phytopathogenic bacterium Agrobacterium tumefaciens transfers DNA to host plants to cause crown gall disease. Knowledge of the molecular mechanism underlying gene transfer, subsequently led to the development of plant transgene technology, an indispensable tool in fundamental plant research and plant improvement. In the early 1980s, Marc Van Montagu founded a start-up company, Plant Genetic Systems, which successfully developed insect-resistant plants, herbicide-tolerant plants and a hybrid seed production system based on nuclear male sterility. Even before the first transgenic plant had been produced, Marc Van Montagu realized that the less developed countries might benefit most from plant biotechnology and throughout his subsequent career, this remained a focus of his efforts. After becoming emeritus professor, he founded the Institute of Plant Biotechnology Outreach (IPBO), which aims to raise awareness of the major role that plant biotechnology can play in sustainable agricultural systems, especially in less developed countries. Marc Van Montagu has been honored with many prizes and awards, the most recent being the prestigious World Food Prize 2013. In this paper, we look to the past and present of plant biotechnology and to the promises this technology holds for the future, on the basis of the personal perspective of Marc Van Montagu.

In Vitro Antibacterial Activity of Cysteine Protease Inhibitor from Kiwifruit (Actinidia deliciosa).

The need for replacing traditional pesticides with alternative agents for the management of agricultural pathogens is rising worldwide. In this study, a cysteine proteinase inhibitor (CPI), 11kDa in size, was purified from green kiwifruit to homogeneity. We examined the growth inhibition of three plant pathogenic Gram-negative bacterial strains by kiwi CPI and attempted to elucidate the potential mechanism of the growth inhibition. CPI influenced the growth of phytopathogenic bacteria Agrobacterium tumefaciens (76.2% growth inhibition using 15μM CPI), Burkholderia cepacia (75.6% growth inhibition) and, to a lesser extent, Erwinia carotovora (44.4% growth inhibition) by inhibiting proteinases that are excreted by these bacteria. Identification and characterization of natural plant defense molecules is the first step toward creation of improved methods for pest control based on naturally occurring molecules.

Agrobacterium tumefaciens: From crown gall tumors to genetic transformation

The phytopathogenic bacterium Agrobacterium tumefaciens is the causative agent of crown gall disease on a broad range of plant species. For more than a century this pathogen has fascinated biologists for various reasons. It has been believed that disclosing the mystery of the crown gall tumour disease in plants might help to understand the mechanisms of oncogenesis in general, and eventually use this knowledge to cure cancer in animals and humans. However, as the performer of the only known case of trans-kingdom DNA transfer, this natural genetic engineer is recognised by nowadays biologists particularly for this feature, and Agrobacterium-mediated genetic transformation has become the preferred method to generate transgenic plants. This review briefly highlights the key steps in DNA transfer during natural A. tumefaciens infection and the subsequent development of crown gall disease. It will focus on the adaptation and use of this proof of principle for the purpose of genetic transformation.

Structural characterization of a group II 2/2 hemoglobin from the plant pathogen Agrobacterium tumefaciens

Within the 2/2 hemoglobin sub-family, no group II 2/2Hbs from proteobacteria have been so far studied. Here we present the first structural characterization of a group II 2/2Hb from the soil and phytopathogenic bacterium Agrobacterium tumefaciens ( At-2/2HbO). The crystal structure of ferric At-2/2HbO (reported at 2.1 Å resolution) shows the location of specific/unique heme distal site residues (e.g., His(42)CD1, a residue distinctive of proteobacteria group II 2/2Hbs) that surround a heme-liganded water molecule. A highly intertwined hydrogen-bonded network, involving residues Tyr(26)B10, His(42)CD1, Ser(49)E7, Trp(93)G8, and three distal site water molecules, stabilizes the heme-bound ligand. Such a structural organization suggests a path for diatomic ligand diffusion to/from the heme. Neither a similar distal site structuring effect nor the presence of distal site water molecules has been so far observed in group I and group III 2/2Hbs, thus adding new distinctive information to the complex picture of currently available 2/2Hb structural and functional data. This article is part of a Special Issue entitled: Protein Structure and Function in the Crystalline State.

Proteomic and transcriptomic characterization of a virulence-deficient phosphatidylcholine-negative Agrobacterium tumefaciens mutant

Phosphatidylcholine (PC) is the most abundant phospholipid in eukaryotic membranes, whereas only a limited number of bacteria are able to synthesize PC. Intriguingly, many of the bacteria with PC-containing membranes interact with eukaryotic hosts. PC is one of the major membrane lipids in the phytopathogenic bacterium Agrobacterium tumefaciens. The presence of PC is critical for diverse cellular processes like motility, biofilm formation, stress resistance, and virulence. The exact role of PC in these processes is unknown. Here, we examined the global consequences of the complete loss of PC at the proteomic and transcriptomic levels. Both strategies validated the impaired virulence gene induction responsible for the virulence defect of the PC-deficient mutant. In addition, the proteomic approach revealed a limited subset of proteins with altered abundance including the reduced flagellar proteins FlaA and FlaB, which explains the motility defect of the PC mutant. At the whole-genome level, the loss of PC was correlated with altered expression of up to 13% of all genes, most encoding membrane or membrane-associated proteins and proteins with functions in the extracytoplasmic stress response. Our integrated analysis revealed that A. tumefaciens dynamically remodels its membrane protein composition in order to sustain normal growth in the absence of PC.

PV-4 Prevalence of genotypic resistance to protease and reverse transcriptase inhibitors and genetic diversity in treatment-naïve (HIV1)-infected Moroccan individuals

The unusual mixed valence CuII/CuI coordination polymer based on 2,5-bis(pyridine-2-yl)-1,3,4-thiadiazole [CuI3CuIIL2(SCN)5]n has been prepared by reaction between the thiadiazole ligand (L), CuCl2·2H2O and KSCN in H2O/CH3CN solution. The title complex has been characterized using single-crystal X-ray diffraction, and spectroscopic measurements, as well as Hirshfeld surface analysis. TGA analysis and magnetic measurements were also performed. The polymeric complex crystallizes in monoclinic symmetry and C2/c space group with three independent copper crystallographic sites, trigonal and tetrahedral for CuI and octahedral for CuII. The thermal analysis reveals that this complex is thermally stable up to 200 °C. Magnetic measurements carried out on [CuI3CuIIL2(SCN)5]n complex indicate a paramagnetic behaviour. While this new polymer exhibited a noticeable activity against the phytopathogenic bacteria Agrobacterium tumefaciens, no significant activity was recorded against Pseudomonas syringae pv. syringae and Pseudomonas syringae pv. tobacco nor against the phytopathogenic fungi Verticillium dahlia and Fusarium oxysporum fsp. melonis.

Functional and Expression Analyses of the cop Operon, Required for Copper Resistance in Agrobacterium tumefaciens

The copper resistance determinant copARZ, which encodes a CPx-type copper ATPase efflux protein, a transcriptional regulator, and a putative intracellular copper chaperone, was functionally characterized for the phytopathogenic bacterium Agrobacterium tumefaciens. These genes are transcribed as an operon, and their expression is induced in response to increasing copper and silver ion concentrations in a copR-dependent fashion. Analysis of the copARZ promoter revealed a putative CopR binding box located within the spacer of the -35 and -10 promoter motifs. In vitro, purified CopR could specifically bind to the box. The inactivation of the copARZ operon or copZ reduces the level of resistance to copper but not to other metal ions. Also, the copARZ operon mutant shows increased sensitivity to the superoxide generators menadione and plumbagin. In addition, the loss of functional copZ does not affect the ability of copper ions to induce the copARZ promoter, indicating that CopZ is not involved in the copper-sensing mechanism of CopR. Altogether, the results demonstrate a crucial role for the copARZ operon as a component of the copper resistance machinery in A. tumefaciens.

Expression and Physiological Relevance of Agrobacterium tumefaciens Phosphatidylcholine Biosynthesis Genes

Phosphatidylcholine (PC), or lecithin, is the major phospholipid in eukaryotic membranes, whereas only 10% of all bacteria are predicted to synthesize PC. In Rhizobiaceae, including the phytopathogenic bacterium Agrobacterium tumefaciens, PC is essential for the establishment of a successful host-microbe interaction. A. tumefaciens produces PC via two alternative pathways, the methylation pathway and the Pcs pathway. The responsible genes, pmtA (coding for a phospholipid N-methyltransferase) and pcs (coding for a PC synthase), are located on the circular chromosome of A. tumefaciens C58. Recombinant expression of pmtA and pcs in Escherichia coli revealed that the individual proteins carry out the annotated enzyme functions. Both genes and a putative ABC transporter operon downstream of PC are constitutively expressed in A. tumefaciens. The amount of PC in A. tumefaciens membranes reaches around 23% of total membrane lipids. We show that PC is distributed in both the inner and outer membranes. Loss of PC results in reduced motility and increased biofilm formation, two processes known to be involved in virulence. Our work documents the critical importance of membrane lipid homeostasis for diverse cellular processes in A. tumefaciens.

Genome analysis of Agrobacterium tumefaciens: construction of physical maps for linear and circular chromosomal DNAs, determination of copy number ratio and mapping of chromosomal virulence genes.

The phytopathogenic bacterium Agrobacterium tumefaciens is unique in that it possesses both linear and circular DNA chromosomes in addition to a plant-tumor-inducing (Ti) plasmid. We analyzed the two chromosomal DNA molecules in strain MAFF301001, whose Ti plasmid has already been sequenced completely. Physical maps of the chromosomal DNAs were constructed by Southern hybridization experiments using Pme I and Swa I fragments and short fragments bridging the Swa I fragments with special care to avoid any missing fragment. Hybridization with 16S rDNA probe showed one rDNA locus on the linear chromosome and two loci on the circular chromosome. For this bacterium to be pathogenic, not only Ti plasmid but also chromosomal genes are required. The chromosomal virulence (chv) genes (chvA, chvB, chvD, chvE, chvG, chvH, and chvI) and the chromosomal genes affecting the virulence [acvB, pgm(exoC), glgP, miaA, and ros] were successfully mapped onto 5 different regions in the chromosomal physical maps. These chv genes and the chromosomal genes affecting the virulence other than pgm and glgP were found on the circular chromosome, whereas the pgm and glgP genes were located on the linear chromosome. In contrast to the large terminal inverted repeats of Streptomyces linear chromosomal DNA, no hybridization signal was detected between left and right terminal fragments of the linear A. tumefaciens chromosome. Quantitative analysis of DNA fragments indicated that the copy numbers of the two chromosomal DNAs and the Ti plasmid are identical.

AGROBACTERIUM AND PLANT GENES INVOLVED IN T-DNA TRANSFER AND INTEGRATION.

The phytopathogenic bacterium Agrobacterium tumefaciens genetically transforms plants by transferring a portion of the resident Ti-plasmid, the T-DNA, to the plant. Accompanying the T-DNA into the plant cell is a number of virulence (Vir) proteins. These proteins may aid in T-DNA transfer, nuclear targeting, and integration into the plant genome. Other virulence proteins on the bacterial surface form a pilus through which the T-DNA and the transferred proteins may translocate. Although the roles of these virulence proteins within the bacterium are relatively well understood, less is known about their roles in the plant cell. In addition, the role of plant-encoded proteins in the transformation process is virtually unknown. In this article, I review what is currently known about the functions of virulence and plant proteins in several aspects of the Agrobacterium transformation process.

A homolog of the Rhizobium meliloti nitrogen fixation gene fixN is involved in the production of a microaerobically induced oxidase activity in the phytopathogenic bacterium Agrobacterium tumefaciens.

Hybridization analysis using the Rhizobium meliloti nitrogen fixation gene fixN as a probe revealed the presence of a homologous DNA region in the phytopathogenic bacterium Agrobacterium tumefaciens. Hybridization signals were also detected with total DNAs of Rhizobium leguminosarum bv. phaseoli, Rhodobacter capsulatus and Escherichia coli, but not those of Xanthomonas campestris pv. campestris and Pseudomonas putida. The hybridizing fragment from A. tumefaciens was cloned and sequenced. The predicted gene product of one of the two open reading frames identified on the sequenced fragment shows homology to FixN of different Rhizobiaceae as well as a low but significant similarity to subunit I of heme copper oxidases from various bacteria. The presence of five strictly conserved histidine residues previously implicated in forming ligands to heme and CuB in oxidases and the predicted membrane topology provide evidence that the A. tumefaciens fixN-like gene product is a component of the heme copper oxidase superfamily. The incomplete open reading frame starting only 8 nucleotides downstream of the fixN-like gene exhibits homology to Rhizobium fixO. Using an uidA (GUS) gene fusion it could be shown that the A. tumefaciens fixN-like gene is preferentially expressed under microaerobic conditions. Expression of the uidA fusion is abolished in R. meliloti fixJ and fixK mutants, indicating that an Fnr-like protein is involved in transcriptional regulation of the fixN-like gene in A. tumefaciens. The presence of an upstream DNA sequence motif identical to the Fnr-consensus binding site (anaerobox) further supports this hypothesis. A. tumefaciens mutated in the fixN-like gene shows decreased TMPD-specific oxidase activity under microaerobic conditions, indicating that the fixN-like gene or operon codes for proteins involved in respiration under reduced oxygen availability.

Occurrence of enzymes involved in biosynthesis of indole-3-acetic acid from indole-3-acetonitrile in plant-associated bacteria, Agrobacterium and Rhizobium.

The occurrence of a hitherto unknown pathway involving the action of two enzymes, a nitrile hydratase and an amidase for the biosynthesis of indole-3-acetic acid was discovered in phytopathogenic bacteria Agrobacterium tumefaciens and in leguminous bacteria Rhizobium. The nitrile hydratase acting on indole-3-acetonitrile was purified to homogeneity through only two steps from the cell-free extract of A. tumefaciens. The molecular mass of the purified enzyme estimated by HPLC was about 102 kDa, and the enzyme consisted of four subunits identical in molecular mass. The enzyme exhibited a broad absorption spectrum in the visible range with absorption maxima at 408 nm and 705 nm, and it contained cobalt and iron. The enzyme stoichiometrically catalyzed the hydration of indole-3-acetonitrile into indole-3-acetamide with a specific activity of 13.7 mol per min per mg and a Km of 7.9 microM.

Crown Gall Disease and Hairy Root Disease

The neoplastic diseases crown gall and hairy root are incited by the phytopathogenic bacteria Agrobacterium tumefaciens and Agrobacterium rhizogenes, respectively. Although the molecular mechanism of T-DNA transfer to the plant most likely is the same for both species, the physiological basis of tumorigenesis is fundamentally different. Crown gall tumors result from the over-production of the phytohormones auxin and cytokinin specified by A. tumefaciens T-DNA genes. Although the T-DNA of some Riplasmids of A. rhizogenes contains auxin biosynthetic genes, these loci are not always necessary for hairy root formation. Recent experiments suggest that hairy root tumors result from the increased sensitivity of transformed cells to endogenous auxin levels. An understanding of hairy root tumorigenesis will likely result in an increased knowledge of plant developmental processes.