CHARACTERIZATION OF LIPOXYGENASE GENES AND OXYLIPIN PROFILE IN ASPERGILLUS OCHRACEUS.

In previous works the lipoxygenase (lox) profile of Aspergillus ochraceus (wt, OTA producer), was characterized. A lox fragment of 673 bp - DQ087531 (47-78% homology with other fungal lipoxygenase sequences), was found and studied. This fragment was used to generate a Dlox mutant which showed delayed conidia formation and increase of sclerotia production. In addition, low lipoperoxide formation in the mycelium, reduced lipoxygenase activity and strong reduction of OTA biosynthesis were observed in the mutant in comparison with wt. The use of lipoxygenase inhibitors (SHAM, salicylhydroxamic acid and resveratrol) allowed to further study the role played by lipoperoxides alteration in OTA synthesis by A. ochraceus. Resveratrol showed antioxidant properties and inhibition effect on lipoxygenase and cicloxygenase in humans. In A. ochraceus wt the use of this LOXinhibitors led to a delay of lipoxygenase activity and oxylipin profile in comparison with Dlox showing a marked reduction of lipoperoxides and OTA formation. Supplementation of culture media with several fatty acids was also investigated. The complete lox gene sequence was obtained with several techniques such as Genome Walker Library, Reverse PCR and 5'-3' RACE. In conclusion, the results obtained with both wt and Dlox indicate that lipoperoxidation plays a major role in controlling OTA biosynthesis in A. ochraceus.