The Crz1 transcription factor regulates lipid metabolism and fumonisin production in Fusarium verticillioides

Calcineurin, a key player in calcium-dependent signal transduction pathways of eukaryotes, modulates colony growth, stress response and pathogenicity in fungi (Thewes, 2014). Here we investigated the role of the fungal protein Crz1, a downstream transcription factor of the calcineurin pathway, in the fumonisin-producing fungus Fusarium verticillioides. Previous studies have shown that the production of fumonisins in Fusarium is related to the presence in the growth medium of some specific fatty acids (FAs) and oxylipins (i.e. oxidized FAs) which are released by both the plant and the fungus, and that play pivotal functions in the crosstalk between host and pathogens (Dall'Asta et al., 2012; Scala et al., 2014). In this study, we report the involvement of Crz1 in the regulation of both lipid metabolism and fumonisin production during the F. verticillioides-maize interaction. F. verticillioides crz1Δ strains showed higher membrane permeability and susceptibility to ionic stress when compared to the wild type or the crz1Δ+crz1 complemented strains. Through a mass spectrometry approach, we also found that the deletion of crz1 was consistently associated with an overall reduction in oxylipin, FA and mycotoxin content during maize infection. We postulate that Crz1 is required for the proper generation of signalling lipid molecules (e.g. FAs or oxylipins) which in turn activate fumonisin biosynthesis in F. verticillioides.