Fatty acid composition and metabolism in the maize pathogen Fusarium verticillioides

Fatty acids are important signalling molecules, both in naïve and in modified forms, additionally to being main constituents of plasma membranes. Free fatty acids can be modified by the action of different enzymes: elongases can add C₂ to the carbon chain, desaturases catalyse the carbon/carbon double bond formation, while linoleate diol synthases and lipoxygenases promote the formation of hydroperoxides (i.e. oxylipins). Our work mainly aims studying fungal fatty acid metabolism during the host-pathogen interaction Fusarium verticillioides-Zea mays.

Oxylipins are known as modulators of primary metabolic functions in fungi and key players during host–pathogen communication (Tsitsigiannis & Keller, 2007; Scala et al., 2014). Despite this, little is known on their precursors and on the enzymatic processes leading to their synthesis.

In the present study, we compared the expression levels of several fatty acid desaturase and elongase genes with fungal FA composition during fungal growth in semi-vitro (media amended with cracked maize). The expression of FA-related genes as well as FA composition appear tightly coordinated under these experimental conditions. Interestingly, by using an in silico approach, we found that 5’UTRs of desaturase, elongase and oxylipin-synthesis genes contained one or more putative CDRE (Calcineurin dependent response elements) consensus sequences, linking the activity of the Crazy1 (Crz1) transcription factor to oxylipin synthesis and FA metabolism. To explore this idea, we generated crz1D deletion mutants and found that the absence of the transcription factor has negative implication on the fatty acid content. The lipidomic profile can be correlated to the expression of the fatty acid-shaping gene. These results combined with reduced capacity of growth and germination rate could let to hypothesize that the imbalance of the fatty acids can affect the pathogen fitness.