LDS1-produced oxylipins are negative regulators of growth, conidiation and fumonisin synthesis in the fungal maize pathogen Fusarium verticillioides

Abstract

Oxylipins are fatty acid-derived signaling compounds produced by all eukaryotes so far investigated; in mycotoxigenic fungi, they modulate toxin production and interactions with the host plants. Among the many enzymes responsible for oxylipin generation, Linoleate Diol Synthase 1 (LDS1) produces mainly 8-hydroperoxyoctadecenoic acid and subsequently different di-hydroxyoctadecenoic acids. In this study, we inactivated a copy of the putative LDS1 ortholog (acc. N. FVEG_09294.3) of Fusarium verticillioides, with the aim to investigate its influence on the oxylipin profile of the fungus, on its development, secondary metabolism and virulence. LC-MS/MS oxylipin profiling carried out on the selected mutant strain revealed significant quali-quantitative differences for several oxylipins when compared to the WT strain. The Fvlds1-deleted mutant grew better, produced more conidia, synthesized more fumonisins and infected maize cobs faster than the WT strain. We hypothesize that oxylipins may act as regulators of gene expression in the toxigenic plant pathogen F. verticillioides, in turn causing notable changes in its phenotype. These changes could relate to the ability of oxylipins to re-shape the transcriptional profile of F. verticillioides by inducing chromatin modifications and exerting a direct control on the transcription of secondary metabolism in fungi.

Resistance to Fusarium verticillioides and fumonisin accumulation in maize inbred lines involves an earlier and enhanced expression of lipoxygenase (LOX) genes

“…Functional and physiological analyses of LOXs were firstly addressed to dicots and recent researches aimed to unravel the role of LOX in plant-pathogen cross-talk with the use of maize mutants (Christensen et al, 2013;Gao et al, 2007) and Fv mutants (Lanubile et al, 2013;Scala et al, 2014). Our study provides the first insight of the overexpression of genes involved in the LOX pathway in resistant (R) and susceptible (S) maize lines, tested in field condition over a time course of 21 days after inoculation with Fv.…”

Oxylipins from both pathogen and host antagonize jasmonic acid‐mediated defence via the 9‐lipoxygenase pathway in Fusarium verticillioides infection of maize

“…Although the functional and physiological characterization of LOXs was first addressed in dicots, only recently have studies aimed to unravel the role of oxylipins in monocot–pathogen interactions with the use of maize mutants (Christensen et al ., ; Gao et al ., ) and F. verticillioides mutants (Scala et al ., ). The analysis of the maize knock‐out lox3 mutant provided convincing genetic evidence that the functional host LOX3 isoform and its 9‐oxylipin products are required for normal biosynthesis of fumonisin B1 and conidiation by F. verticillioides (Gao et al ., ).…”

“…The role of F. verticillioides ‐derived oxylipins in endogenous processes was established by the inactivation of the LDS1 gene ( LDS1 ), where the deletion mutant (hereafter referred to as ΔFv lds1 D) was perturbed in development, secondary metabolism and virulence (Scala et al ., ). It was uncovered that LDS1‐derived oxylipins act as negative regulators of fumonisin synthesis.…”

Volatile compounds released by maize grains and silks in response to infection by Fusarium verticillioides and its association with pathogen resistance

“…The most susceptible genotypes exhibited higher contents of linoleic acid and higher production of VOCs compared to those of moderately resistant genotypes. Recent studies have shown that the composition of total fatty acids can influence infections of F. verticillioides and fumonisin accumulation in maize under field conditions (Scala et al ., ). Similar results were reported by Dall'Asta et al .…”