Reactive Oxygen Species (ROS) and lipoperoxides in Aspergillus parasiticus stimulated aflatoxin production and the expression of transcription factors related to oxidative stress. These factors promoted the transcription of genes encoding antioxidant-related enzymes. In A. parasiticus cells oxidative stress, induced by ROS and lipoperoxides, appeared to be perceived and transduced by Apyap1 (Yap1 orthologue) to primes antioxidant defense activities. 916;apyap1 mutant had an altered perception of oxidative stress and presented a precocious and increased production of aflatoxin in comparison to wild type (WT). Also in A. ochraceus (MPV 2037 strain - OTA producer) hydroperoxides of linoleic acid are able to modulate ochratoxin A (OTA) production (Punelli et al., 2007). The correlation between lipoperoxides and OTA biosynthesis was analyzed in previous works (Punelli et al., 2007) and a 916;aolox-like (lipoxygenase mutant) presented a delay in the sporulation and OTA production. In this study a correlation among lipoperoxidation, activity of antioxidant defence system and OTA biosynthesis was more deeply evidenced and new approaches were used to analyze the function of oxidative stress in fungal cells. Oxidant inducers like Menadione 0.1 and 0.5 mM, CCl4 0.5% v/v, H2O2 10 mM, tBOOH 100 mM were used to test their effect on OTA production by WT. Furthermore the construction of 916;aoyap-like mutant was perfomed to investigate the correlation between oxidative stress and OTA biosynthesis. To analyze the A. ochraceus genome, several primers were used (Aoyap, Aocat and Aosod for e rev). The transcription level in WT and mutant was studied by reverse PCR analysis. In A. ochraceus, OTA producer, a 657 bp sequence of aoyap-like (accession number EU045307 - 82% of aa homology with A. fumigatus yap1), a 309 bp Aocat-like (95-100% of aa homology with A. clavatus CatA) and 233 bp Cu-Zn Aosod-like (77% of aa homology with A. fumigatus Cu,Zn SOD) were characterized and partially cloned and the activity and expression of these enzymes were analyzed in mycelia. The results obtained show that a delay in the sporulation was observed in the mutant and the best antioxidant enzymes stimulator were Menadione 0.5 mM and CCl4 0.5% v/v, also the OTA production was affected differently by the oxidant inducers.
Full conference title:
9th EUROPEAN CONFERENCE ON FUNGAL GENETICS
- ECFG 9th (2008)