Home  About us  Contact
 

Crown Gall (crown + gall)

Distribution by Scientific Domains
Life Sciences100%

Selected Abstracts

Strain E26 of Agrobacterium vitis, a Biological Control Agent of Grapevine Crown Gall, Does Not Contain virA and virG Pathogenic Determinants

JOURNAL OF PHYTOPATHOLOGY, Issue 11-12 2009
Qing Wei
Abstract Risk assessment of biological control agents (BCAs) for the control of plant diseases in the field and/or laboratories has now become a necessary procedure before developing and producing novel BCAs. Agrobacterium vitis strain E26 is a promising potential biocontrol agent of grapevine crown gall disease. However, much less is understood about its safety or environmental risks. In this study, polymerase chain reaction (PCR) and Southern blot analyses were used to determine whether five essential virulence genes (virA, virG, iaaH, iaaM and ipt) were present in strain E26. Primers and probes were designed based on the conserved regions of each gene. The overall results obtained indicated that A. vitis strain E26 does not contain the virA and virG determinants, suggesting that this strain would be unlikely to elicit crown gall symptoms in either host or non-host plants. It seems that the iaaH, iaaM, or ipt gene were not present in strain E26 either. An applicable new approach combining PCR and Southern blot analyses to examine the pathogenicity of potential BCAs, particularly BCAs from the genus of Agrobacterium spp. was described. [source]

DNA and protein transfer from bacteria to eukaryotes, the agrobacterium story

MOLECULAR PLANT PATHOLOGY, Issue 1 2000
The 18th Bateson Memorial Lecture
Agrobacterium is a well-studied plant pathogen, which has the unique ability to transfer DNA and protein into a number of eukaryotes. The DNA is integrated randomly into the plant genome where it is expressed, thereby leading to the disease crown gall. This system is a paradigm for the interaction of a number of plant and animal pathogens which transfer proteins into their host cells. In Agrobacterium, the tumour inducing (Ti) plasmid codes for the functions specifically required for the transfer process. These genes, termed virulence or vir genes, are activated by plant signal molecules acting through a two component regulatory system. A key structure coded by 11 genes of the vir B operon is a pilus, synthesized at 20 °C, but poorly at 25 °C. How this pilus functions in DNA and protein transfer is unclear, but homologous genes are found in many animal pathogens. In addition to Ti plasmid-encoded vir genes, chromosomal virulence genes have also been identified. However, these mutations are often pleiotropic because they involve both the normal physiology of Agrobacterium as well as the metabolism of Agrobacterium when it is associated with plant cells. Based on 16S ribosomal RNA sequencing, Agrobacterium is closely related to the intracellular pathogen of animals, Brucella. Several chromosomal mutations of Agrobacterium required for virulence in plants are also required for invasion of animal host cells by Brucella. [source]

Evidence of pAgK84 transfer from Agrobacterium rhizogenes K84 to natural pathogenic Agrobacterium spp. in an Italian peach nursery

PLANT PATHOLOGY, Issue 4 2009
A. Raio
Nine Italian peach nurseries, which use Agrobacterium rhizogenes strain K84 to protect plants from crown gall, were monitored for three years with the aim of determining whether transconjugant populations may arise following plasmid exchanges between K84 and autochtonous soil agrobacteria. Six hundred and seventy-eight Agrobacterium isolates were obtained from 120 tumours developed on apricot and peach rootstocks that had been treated in pre-planting with the antagonist. Agrobacteria were characterized for pathogenicity, biovar, opine catabolism and agrocin 84 sensitivity. Colony hybridization was used for screening the isolates harbouring plasmids pTi and/or pAgK84. Analysis of plasmid content and Southern blotting were performed on putative transconjugant agrobacteria found in tumours collected from one nursery where a biological control breakdown was observed. The RFLP analysis of 16S + IGS regions showed that pAgK84 was transferred from the antagonist to virulent and avirulent soil agrobacteria belonging to different ribotypes. Pathogenic transconjugants, inoculated on GF677 rootstocks, were not controlled in vivo by K84 and stably maintained pTi and pAgK84 in the bacterial cells for at least one year. At the end of a biocontrol trial, new transconjugant tumorigenic agrobacteria originated by the transfer of pAgK84 to the pathogen. Virulent and avirulent transconjugants may represent a real threat for biological control by K84 strain since all of them produced agrocin and were insensitive to it. Survival in soil of these populations could make the future application of K84 ineffective. [source]

Characterization of agrobacteria from weeping fig (Ficus benjamina)

PLANT PATHOLOGY, Issue 5 2001
A. Zoina
Ficus benjamina plants, galled both at epi- and hypogeous parts, were observed in Italy and in The Netherlands, and these were the first records of the appearance of weeping fig crown gall in Europe. A total of 241 Agrobacterium isolates was obtained from 41 tumours and studied for their morphological, physiological and phytopathological characters. Two main groups of agrobacteria were distinguished by their colony morphology and through classical biovarietal tests that allowed allocation of 86 isolates into biovar 1 and 155 into an intermediate biovar rather different from any of the three biovars defined for agrobacteria. Most of the isolates were unable to utilize mannopine, nopaline or octopine as C and N sources; only 62 strains utilized nopaline. However, when nonopine-utilizing strains were inoculated into F. benjamina, only nopaline was detected in the developing tumours. BIOLOG ML 1Ō system analysis applied to 50 representative strains allowed identification of the biovar 1 isolates as Agrobacterium tumefaciens and most of the intermediate biovar isolates as the newly proposed species Agrobacterium fici. Analysis of sensitivity to a set of 14 antibiotics confirmed the allocation of the 50 strains into two well defined main clusters matching the BIOLOG identification. Out of 141 tumorigenic isolates, 66 were sensitive in vitro to agrocine 84, but four of these strains showed scarce or no sensitivity to the antagonist A. radiobacter K84 when tested in fig plants. The two types of agrobacteria could usually be isolated from the same tumours. Tumorigenic strains were able to induce tumours in six herbaceous plant species, in eight to 10 out of 12 woody plants and in six to eight out of nine Ficus species, indicating a wide host-range Ti plasmid. Agrobacteria were able to survive and move in the vascular system of galled ficus plants and to induce tumour growth in stem-cutting propagated plants. Moreover, agrobacteria were detected in many healthy F. benjamina plants as part of the endophytic microflora. These findings suggest potential for spread of the disease through latently infected plant propagation material produced as cuttings or by tissue culture. [source]

A role for PSK signaling in wounding and microbial interactions in Arabidopsis

PHYSIOLOGIA PLANTARUM, Issue 4 2010
Maaria Loivamäki
PSK- , is a disulfated peptide that acts as a growth factor in plants. PSK- , is derived from preproproteins which are encoded by five PSK precursor genes in Arabidopsis thaliana (L.) Heynh and is perceived by leucine-rich repeat receptor kinases. Arabidopsis has two PSK receptor genes, PSKR1 and PSKR2. Although ligand and receptor are well characterized, the biological functions of PSK signaling are not well understood. Using reporter lines and receptor knockout mutants of Arabidopsis, a role for PSK signaling in biotic interactions and in wounding was analyzed. Treatment of Arabidopsis leaves with the fungal elicitor E-Fol, or the fungal pathogens Alternaria brassicicola and Sclerotinia sclerotiorum resulted in induction of PSK2 and PSKR1 as shown by promoter:GUS analysis. Wounding of hypocotyls or leaves induced PSK3:GUS, PSK5:GUS and PSKR1:GUS expression indicating that PSK precursor genes are differentially regulated in response to specific stresses. The receptor knockout lines pskr1-3 and pskr2-1 showed significantly reduced photosynthesis in response to the fungal elicitor E-Fol which indicates that fungal defence is impaired. pskr1-3 plants further showed reduced growth of crown galls after infection with Agrobacterium tumefaciens. A role for PSK signaling in Agrobacterium tumefaciens tumor growth was supported by the finding that PSK precursor genes and PSKR1 are expressed in crown galls. Overall, the results indicate that PSK signaling may play a previously undescribed role in pathogen or herbivore interactions and is crucial for Agrobacterium -induced cell proliferation in crown gall formation. [source]