Adenylyl cyclase regulates heavy metal sensitivity, bikaverin production and plant tissue colonization in Fusarium proliferatum

Abstract

A homologue of the adenylyl cyclase (AC) gene of Neurospora crassa, named Fpacy1 was cloned from the genomic library of Fusarium proliferatum ITEM 2287 by screening the library with a DNA fragment amplified by using PCR primers designed from conserved sequences of the catalytic domain of AC genes from other fungi. The deduced FPACY1 protein had 53-77% identity with the AC proteins of other fungi. DeltaFpacy1 mutants obtained by targeted gene disruption showed retarded vegetative growth, increased conidiation and delayed conidial germination. Colonization capability of the mutants, assessed on maize seedlings and tomato fruits also was adversely affected. In sexual crosses the AC mutants retained full male fertility, but their female fertility decreased significantly. Disruption of Fpacy1 abolished vegetative self-incompatibility, suggesting that the AC gene is involved in multiple developmental processes related to vegetative growth, as well as sexual and parasexual events. The elevated thermo- and H(2)O(2)-tolerance of the DeltaFpacy1 mutants was coupled to an increased sensitivity towards Cd and Cu, indicating that the cAMP signaling pathway may have both negative and positive regulatory roles on the stress response mechanisms of fungal cells. When grown under nitrogen limitation conditions, the DeltaFpacy1 mutants produced an average of approximately 274 microg g(-1) bikaverin, whereas only traces of this metabolite was detected in the wild type. This finding provides further evidence of the role of the cAMP-PKA pathway in regulating bikaverin production.

Segregation of secondary metabolite biosynthesis in hybrids of Fusarium fujikuroi and Fusarium proliferatum

“…Thus, only F. fujikuroi C1995 produces GAs and fusarins at detectable levels, while only F. proliferatum D4854 produces fumonisin B 1 and fusarubins under the investigated conditions. Both strains produce small amounts of bikaverin, a red pigment typical for species of the GFC (Wiemann et al, 2009;Kohut et al, 2010), while we found high amounts of the fusarubins, a second group of red pigments, in F. proliferatum D4854 (Fig. 4).…”

“…Due to the significantly different production capacity of fusarubins between the parental strains, fusarubins, rather than bikaverin, were analyzed in the progeny. Previously, a red pigment produced under acidic conditions in another F. proliferatum strain was described as bikaverin based solely on spectrofluorimetric measurements (Kohut et al, 2010). It would be interesting to perform more precise HPLC and MS analyses to determine whether the analyzed pigment was bikaverin or fusarubins.…”

Role of MAP Kinase Signaling in Secondary Metabolism and Adaptation to Abiotic/Fungicide Stress in Fusarium

“…Previous studies in N. crassa demonstrated that cAMP signaling and HOG1 MAPK signaling play opposite role in respect to oxidative stress response: disturbances in the cAMP and the HOG1 pathways result in increased and decreased H 2 O 2 tolerance, respectively. In F. proliferatum and F. verticillioides, disruption of Acy1, the adenylyl cyclase gene resulted in enhanced resistance to heat shock and oxidative stress (Kohut et al, 2010;Choi and Xu, 2010). However, in contrast to these data, the acyAmutants of F. fujikuroi MP-C were more sensitive to H 2 O 2 than the wild type .…”

“…On the contrary, fumonisin B1 production was not regulated by cAMP signaling either in F. proliferatum (Kohut et al, 2010) or F. verticillioides (Choi and Xu, 2010). This signaling route regulates, however negatively regulates the production of bikaverin, another polyketide metabolite in Fusarium species (Kohut et al, 2010;Choi and Xu, 2010;García-Martínez et al, 2011). Moreover, the production of another secondary metabolite such as carotenoids is upregulated in Fusarium species not only by cAMP signaling (García-Martínez et al, 2011) but other regulatory elements related to sexual reproduction (Ádám et al, 2011).…”

“…In a more recent study Fvmk1, a PMK-type MAPK gene was identified as a positive regulator of fumonisin B1 production in F. verticillioides (Zhang et al, 2011). On the contrary, fumonisin B1 production was not regulated by cAMP signaling either in F. proliferatum (Kohut et al, 2010) or F. verticillioides (Choi and Xu, 2010). This signaling route regulates, however negatively regulates the production of bikaverin, another polyketide metabolite in Fusarium species (Kohut et al, 2010;Choi and Xu, 2010;García-Martínez et al, 2011).…”