Individual and combined roles of malonichrome, ferricrocin, and TAFC siderophores in Fusarium graminearum pathogenic and sexual development

Abstract

Intra- and extracellular iron-chelating siderophores produced by fungal non-ribosomal peptide synthetases have been shown to be involved in reproductive and pathogenic developmental processes and in iron and oxidative stress management. Here we report individual and combined contributions of three of these metabolites to developmental success of the destructive cereal pathogen Fusarium graminearum. In previous work, we determined that deletion of the NPS2 gene, responsible for intracellular siderophore biosynthesis, results in inability to produce sexual spores when mutants of this homothallic ascomycete are selfed. Deletion of the NPS6 gene, required for extracellular siderophore biosynthesis, does not affect sexual reproduction but results in sensitivity to iron starvation and oxidative stress and leads to reduced virulence to the host. Building on this, we report that double mutants lacking both NPS2 and NPS6 are augmented in all collective phenotypes of single deletion strains (i.e., abnormal sexual and pathogenic development, hypersensitivity to oxidative and iron-depletion stress), which suggests overlap of function. Using comparative biochemical analysis of wild-type and mutant strains, we show that NPS1, a third gene associated with siderophore biosynthesis, is responsible for biosynthesis of a second extracellular siderophore, malonichrome. nps1 mutants fail to produce this metabolite. Phenotypic characterization reveals that, although single nps1 mutants are like wild-type with respect to sexual development, hypersensitivity to ROS and iron-depletion stress, and virulence to the host, triple nps1nps2nps6 deletion strains, lacking all three siderophores, are even more impaired in these attributes than double nps2nps6 strains. Thus, combinatorial mutants lacking key iron-associated genes uncovered malonichrome function. The intimate connection between presence/absence of siderophores and resistance/sensitivity to ROS is central to sexual and pathogenic development.

A spatial temporal analysis of the Fusarium graminearum transcriptome during symptomless and symptomatic wheat infection

“…B). In F. graminearum , the absence of NPS6 or NPS1 , which are required for the production of TAFC and malonichrome, respectively, results in a loss in virulence and, in the case of NPS6 , the wheat plant subsequently mounts an enhanced defensive response (Oide et al ., ). In contrast, the loss of NPS2 , responsible for ferricrocin biosynthesis, has no impact on virulence (Oide et al ., ).…”

“…A and File S2, see Supporting Information). Fusarium graminearum produces at least two classes of toxic and non‐toxic secondary metabolites, which are known to be required for F. graminearum virulence on wheat, namely the mycotoxin DON and the siderophores TAFC and malonichrome (Brown and Hammond‐Kosack, ; Oide et al ., ; Proctor et al ., ).…”

“…More specifically, hyphal exposure to a plant defence‐activated oxidative burst, which often represents the plant's immediate response to the detection of a fungal invader (Lamb and Dixon, ), may be reduced in the presence of secreted siderophores. The reductive iron assimilation pathway, which can sustain life in the absence of siderophores, is insufficient to permit pathogenicity (Oide et al ., ), again demonstrating the importance of TAFC and malonichrome to the establishment of infection. A fungal siderophore from Colletotrichum graminicola also acts as a pathogen‐associated molecular pattern, activating plant immunity (Albarouki et al ., ).…”

Comparative “Omics” of theFusarium fujikuroiSpecies Complex Highlights Differences in Genetic Potential and Metabolite Synthesis

“…NRPS1 , NRPS2 , NRPS6 , NRPS17 , and NRPS36 are likely responsible for the production of malonichrom, fericrocin, fusarinine, ferrichrome, and ferrirhodin siderophores, respectively, based on sequence homology (Bushley and Turgeon 2010; Munawar et al 2013; Hansen et al 2015; Oide et al 2015). Only two of the corresponding NRPS genes, NRPS2 and NRPS6 , are present in all five FFC members examined (supplementary table S1, Supplementary Material online).…”

In silico prediction and characterisation of secondary metabolite clusters in the plant pathogenic fungus Verticillium dahliae

“…A distinct clade clearly separated NRPSs from the PKS-NRPSs in the phylogenetic tree (Figure 4). VdNprsl grouped in a clade with NPS2, which is involved in the synthesis of the intracellular siderophore ferricrocin of Fusarium pseudograminearum and Cochliobolus heterostrophus (Tobiasen et al, 2007; Sieber et al, 2014; Oide et al, 2015). VdNprs2 clusters with NRPS4, which is responsible for the synthesis of the extracellular siderophore triacetylfusarinine C (TAFC) by A. fumigatus (Schrettl et al, 2007).…”