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Lopez-Berges M.S.,University of Cordoba, Spain | Capilla J.,Rovira i Virgili University | Turra D.,University of Cordoba, Spain | Schafferer L.,Innsbruck Medical University | And 7 more authors.
Plant Cell

Soilborne fungal pathogens cause devastating yield losses and are highly persistent and difficult to control. During the infection process, these organisms must cope with limited availability of iron. Here we show that the bZIP protein HapX functions as a key regulator of iron homeostasis and virulence in the vascular wilt fungus Fusarium oxysporum. Deletion of hapX does not affect iron uptake but causes derepression of genes involved in iron-consuming pathways, leading to impaired growth under iron-depleted conditions. F. oxysporum strains lacking HapX are reduced in their capacity to invade and kill tomato (Solanum lycopersicum) plants and immunodepressed mice. The virulence defect of DhapX on tomato plants is exacerbated by coinoculation of roots with a biocontrol strain of Pseudomonas putida, but not with a siderophore-def cient mutant, indicating that HapX contributes to iron competition of F. oxysporum in the tomato rhizosphere. These results establish a conserved role for HapX-mediated iron homeostasis in fungal infection of plants and mammals. © 2012 American Society of Plant Biologists. All rights reserved. Source

Lopez-Berges M.S.,University of Cordoba, Spain | Lopez-Berges M.S.,CSIC - Biological Research Center | Turra D.,University of Cordoba, Spain | Capilla J.,Unitat de Microbiologia | And 7 more authors.
Plant Signaling and Behavior

Soilborne fungal pathogens are highly persistent and provoke important crop losses. During saprophytic and infectious stages in the soil, these organisms face situations of nutrient limitation and lack of essential elements, such as iron. We investigated the role of the bZIP transcription factor HapX as a central regulator of iron homeostasis and virulence in the vascular wilt fungus Fusarium oxysporum. This root-infecting plant pathogen attacks more than hundred different crops and is an emerging human opportunistic invader. Although iron uptake remains unaffected in a strain lacking HapX, de-repression of genes implicated in iron-consuming processes such as respiration, amino acid metabolism, TCA cycle and heme biosynthesis lead to severely impaired growth under iron-limiting conditions. HapX is required for full virulence of F. oxysporum in tomato plants and essential for infection in immunodepressed mice. Virulence attenuation of the ΔhapX strain on tomato plants is more pronounced by co-inoculation of roots with the biocontrol strain Pseudomonas putida KT2440, but not with a mutant deficient in siderophores production. These results demonstrate that HapX is required for iron competition of F. oxysporum in the tomato rhizosphere and establish a conserved role for HapX-mediated iron homeostasis in fungal infection of plants and mammals. © 2013 Landes Bioscience. Source

Van Laer B.,Vrije Universiteit Brussel | Van Laer B.,Structural biology research center | Van Laer B.,European Synchrotron Radiation Facility | Roovers M.,Institute Of Recherches Microbiologiques Jean Marie Wiame | And 16 more authors.
Nucleic Acids Research

Purine nucleosides on position 9 of eukaryal and archaeal tRNAs are frequently modified in vivo by the post-transcriptional addition of a methyl group on their N1 atom. The methyltransferase Trm10 is responsible for this modification in both these domains of life. While certain Trm10 orthologues specifically methylate either guanosine or adenosine at position 9 of tRNA, others have a dual specificity. Until now structural information about this enzyme family was only available for the catalytic SPOUT domain of Trm10 proteins that show specificity toward guanosine. Here, we present the first crystal structure of a full length Trm10 orthologue specific for adenosine, revealing next to the catalytic SPOUT domain also N- and C-terminal domains. This structure hence provides crucial insights in the tRNA binding mechanism of this unique monomeric family of SPOUT methyltransferases. Moreover, structural comparison of this adenosine-specific Trm10 orthologue with guanosine-specific Trm10 orthologues suggests that the N1 methylation of adenosine relies on additional catalytic residues. © The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research. Source

Li W.,Catholic University of Leuven | Estrada-De Los Santos P.,Catholic University of Leuven | Estrada-De Los Santos P.,National Autonomous University of Mexico | Matthijs S.,Vrije Universiteit Brussel | And 6 more authors.
Chemistry and Biology

Under control of the Gac regulatory system, Pseudomonas putida RW10S1 produces promysalin to promote its own swarming and biofilm formation, and to selectively inhibit many other pseudomonads, including the opportunistic pathogen Pseudomonas aeruginosa. This amphipathic antibiotic is composed of salicylic acid and 2,8-dihydroxymyristamide bridged by a unique 2-pyrroline-5-carboxyl moiety. In addition to enzymes for salicylic acid synthesis and activation, the biosynthetic gene cluster encodes divergent type II fatty acid biosynthesis components, unusual fatty acid-tailoring enzymes (two Rieske-type oxygenases and an amidotransferase), an enzyme resembling a proline-loading module of nonribosomal peptide synthetases, and the first prokaryotic member of the BAHD family of plant acyltransferases. Identification of biosynthetic intermediates enabled to propose a pathway for synthesis of this bacterial colonization factor. © 2011 Elsevier Ltd All rights reserved. Source

Roovers M.,Institute Of Recherches Microbiologiques Jean Marie Wiame | Oudjama Y.,Institute Of Recherches Microbiologiques Jean Marie Wiame | Fislage M.,Vrije Universiteit Brussel | Bujnicki J.M.,International Institute of Molecular and Cell Biology in Warsaw | And 3 more authors.

N 2-methylguanosine (m 2G) is found at position 6 in the acceptor stem of Thermus thermophilus tRNA Phe. In this article, we describe the cloning, expression, and characterization of the T. thermophilus HB27 methyltransferase (MTase) encoded by the TTC1157 open reading frame that catalyzes the formation of this modified nucleoside. S-adenosyl-L-methionine is used as donor of the methyl group. The enzyme behaves as a monomer in solution. It contains an N-terminal THUMP domain predicted to bind RNA and contains a C-terminal Rossmann-fold methyltransferase (RFM) domain predicted to be responsible for catalysis. We propose to rename the TTC1157 gene trmN and the corresponding protein TrmN, according to the bacterial nomenclature of tRNA methyltransferases. Inactivation of the trmN gene in the T. thermophilus HB27 chromosome led to a total absence of m 2G in tRNA but did not affect cell growth or the formation of other modified nucleosides in tRNA Phe. Archaeal homologs of TrmN were identified and characterized. These proteins catalyze the same reaction as TrmN from T. thermophilus. Individual THUMP and RFM domains of PF1002 from Pyrococcus furiosus were produced. These separate domains were inactive and did not bind tRNA, reinforcing the idea that the THUMP domain acts in concert with the catalytic domain to target a particular position of the tRNA molecule. Published by Cold Spring Harbor Laboratory Press. Copyright © 2012 RNA Society. Source

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