Bacterial plant pathogens
176 views | +0 today
Follow
Bacterial plant pathogens
Everything about plant pathogenic bacteria
Your new post is loading...
Your new post is loading...
Rescooped by Luisa Castiblanco from Plant Pathogenomics
Scoop.it!

mBio: A TALE of Transposition: Tn3-Like Transposons Play a Major Role in the Spread of Pathogenicity Determinants of Xanthomonas citri and Other Xanthomonads (2015)

mBio: A TALE of Transposition: Tn3-Like Transposons Play a Major Role in the Spread of Pathogenicity Determinants of Xanthomonas citri and Other Xanthomonads (2015) | Bacterial plant pathogens | Scoop.it

Members of the genus Xanthomonas are among the most important phytopathogens. A key feature of Xanthomonas pathogenesis is the translocation of type III secretion system (T3SS) effector proteins (T3SEs) into the plant target cells via a T3SS. Several T3SEs and a murein lytic transglycosylase gene (mlt, required for citrus canker symptoms) are found associated with three transposition-related genes in Xanthomonas citri plasmid pXAC64. These are flanked by short inverted repeats (IRs). The region was identified as a transposon, TnXax1, with typical Tn3 family features, including a transposase and two recombination genes. Two 14-bp palindromic sequences within a 193-bp potential resolution site occur between the recombination genes. Additional derivatives carrying different T3SEs and other passenger genes occur in different Xanthomonas species. The T3SEs include transcription activator-like effectors (TALEs). Certain TALEs are flanked by the same IRs as found in TnXax1 to form mobile insertion cassettes (MICs), suggesting that they may be transmitted horizontally. A significant number of MICs carrying other passenger genes (including a number of TALE genes) were also identified, flanked by the same TnXax1 IRs and delimited by 5-bp target site duplications. We conclude that a large fraction of T3SEs, including individual TALEs and potential pathogenicity determinants, have spread by transposition and that TnXax1, which exhibits all of the essential characteristics of a functional transposon, may be involved in driving MIC transposition. We also propose that TALE genes may diversify by fork slippage during the replicative Tn3 family transposition. These mechanisms may play a crucial role in the emergence of Xanthomonas pathogenicity.


Via Kamoun Lab @ TSL
more...
No comment yet.
Scooped by Luisa Castiblanco
Scoop.it!

Contribution of a harpin protein from Xanthomonas axonopodis pv. citri to pathogen virulence

Contribution of a harpin protein from Xanthomonas axonopodis pv. citri to pathogen virulence | Bacterial plant pathogens | Scoop.it

Xanthomonas axonopodis pv. citri (Xac), the bacterium that causes citrus canker, contains a gene in the hrp [for hypersensitive response (HR) and pathogenicity] cluster that encodes a harpin protein called Hpa1. Hpa1 produced HR in the nonhost plants tobacco, pepper and Arabidopsis, whereas, in the host plant citrus, it elicited a weak defence response with no visible phenotype. Co-infiltrations of Xac with or without the recombinant Hpa1 protein in citrus leaves produced a larger number of cankers in the presence of the protein. To characterize the effect of Hpa1 during the disease, an XacΔhpa1 mutant was constructed, and infiltration of this mutant caused a smaller number of cankers. In addition, the lack of Hpa1 hindered bacterial aggregation both in solution and in planta. Analysis of citrus leaves infiltrated with Hpa1 revealed alterations in mesophyll morphology caused by the presence of cavitations and crystal idioblasts, suggesting the binding of the harpin to plant membranes and the elicitation of signalling cascades. Overall, these results suggest that, even though Hpa1 elicits the defence response in nonhost plants and, to a lesser extent, in host plants, its main roles in citrus canker are to alter leaf mesophyll structure and to aggregate bacterial cells, and thus increase virulence and pathogen fitness. We expressed the N-terminal and C-terminal regions and found that, although both regions elicited HR in nonhost plants, only the N-terminal region showed increased virulence and bacterial aggregation, supporting the role of this region of the protein as the main active domain.

more...
No comment yet.
Scooped by Luisa Castiblanco
Scoop.it!

A novel two-component system PdeK/PdeR regulates c-di-GMP turnover and virulence of Xanthomonas oryzae pv. oryzae

A novel two-component system PdeK/PdeR regulates c-di-GMP turnover and virulence of Xanthomonas oryzae pv. oryzae | Bacterial plant pathogens | Scoop.it

Two-component systems (TCSs) consisting of histidine kinases (HKs) and response regulators (RRs) play essential roles in bacteria to sense environmental signals and regulate cell functions. One type of RR is involved in metabolism of cyclic diguanylate (c-di-GMP), a ubiquitous bacterial second messenger. Although genomic studies predicted a large number of them existing in different bacteria, only a few have been studied. In this work we characterized a novel TCS consisting of PdeK(PXO_01018)/PdeR(PXO_01019) from Xanthomonas oryzae pv. oryzae (Xoo), which causes the bacterial leaf blight of rice. PdeR (containing GGDEF, EAL and REC domains) was shown to have phosphodiesterase (PDE) activity in vitro by colorimetric assays and HPLC analysis. The PDE activity of full-length PdeR needs to be triggered by HK PdeK. Deletion of pdeK or pdeR in Xoo strain PXO99A had attenuated its virulence on rice. ∆pdeK and ∆pdeR secreted less exopolysaccharide (EPS) than the wild type, but there were no changes in terms of motility or extracellular cellulase activity, suggesting the activity of PdeK/PdeR might be specific.

more...
No comment yet.
Scooped by Luisa Castiblanco
Scoop.it!

Top 10 plant pathogenic bacteria in molecular plant pathology

Top 10 plant pathogenic bacteria in molecular plant pathology | Bacterial plant pathogens | Scoop.it
RT @MPPjournal: Top 10 plant pathogenic bacteria in molecular plant pathology MANSFIELD 2012 Molecular Plant Pathology http://t.co/OR9yPIOq...
more...