Project description:The plant pathogen Dickeya chrysanthemi EC16 (formerly known as Petrobacterium chrysanthemi EC16 and Erwinia chrysanthemi EC16) was found to produce a new triscatecholamide siderophore, cyclic trichrysobactin, the related catecholamide compounds, linear trichrysobactin and dichrysobactin, and the previously reported monomeric siderophore unit, chrysobactin. Chrysobactin is comprised of L-serine, D-lysine, and 2,3-dihydroxybenzoic acid (DHBA). Trichrysobactin is a cyclic trimer of chrysobactin joined by a triserine lactone backbone. The chirality of the ferric complex of cyclic trichrysobactin is found to be in the ? configuration, similar to Fe(III)-bacillibactin, which contains a glycine spacer between the DHBA and L-threonine components and is opposite that of Fe(III)-enterobactin, which contains DHBA ligated directly to L-serine.
Project description:We characterized the complete genome of a lytic Dickeya chrysanthemi bacteriophage, DchS19, which was isolated from a soil sample in Sungai Petani, Kedah, Malaysia. The phage, from the Autographviridae family, has a 39,149-bp double-stranded DNA genome containing 49 protein-coding genes and shares 94.65% average nucleotide identity with Erwinia phage pEp_SNUABM_12.
Project description:Pathogenicity of the phytopathogenic enterobacterium Erwinia chrysanthemi, the causative agent of soft rot disease in many plants, is a complex process involving several factors whose production is subject to temporal regulation during infection. After penetrating into its host plant, E. chrysanthemi resides latently in the plant intercellular spaces without provoking any symptoms, and disease occurs only when the environmental conditions are favourable for massive bacterial multiplication and production of plant cell wall degrading enzymes. PecS is a transcriptional regulator of the MarR family that represses production of plant cell wall degrading enzymes. Here, we used microarray analysis to define the PecS regulon and demonstrated that PecS exerts wide-ranging effects on gene expression in E. chrysanthemi. However, the major effects of PecS are largely confined to specific genes that could be linked to pathogenicity and to a group of genes concerned with evading host defences. Among the identified targets are the genes encoding plant cell wall degrading enzymes, secretion systems, the genes involved in flagella synthesis, in biosurfactant synthesis, in oxidative stress response as well as genes encoding toxin-like virulence factors such as NipE and Hemolysin-coregulated proteins. Electromobility shift assays and DNAse I footprinting demonstrated that PecS directly interacts with the regulatory regions of five new targets, ahpC, rhlA, nipE, virK, avrL, that define three different functional classes of genes: oxidative stress response genes (ahpC), biosurfactant synthesis gene (rhlA), genes encoding exported proteins related to other plant associated bacteria proteins (nipE, virK, avrL). Based on this work, we propose a pivotal role of PecS in the switch from a saprophytic to a parasitic lifestyle.
Project description:Embryogenic cultures derived from a zygotic embryo of the avocado cv. Anaheim, were selected for resistance to the culture filtrate (CF) of Rosellinia necatrix, the causal agent of avocado white root rot. Cultures were obtained through recurrent selections in progressively increasing concentrations of fungal CF (from 20% up to 80%).
