Role of Zearalenone Lactonase in Protection of Gliocladium roseum from Fungitoxic Effects of the Mycotoxin Zearalenone

Abstract

Zearalenone is a mycotoxin with estrogenic effects on mammals that is produced by several species of Fusarium . We found that zearalenone and its derivatives inhibit the growth of filamentous fungi on solid media at concentrations of ≤10 μg/ml. The fungitoxic effect declined in the order zearalenone > α-zearalenol > β-zearalenol. The mycoparasitic fungus Gliocladium roseum produces a zearalenone-specific lactonase which catalyzes the hydrolysis of zearalenone, followed by a spontaneous decarboxylation. The growth of G. roseum was not inhibited by zearalenone, and the lactonase may protect G. roseum from the toxic effects of this mycotoxin. We inactivated zes2 , the gene encoding zearalenone lactonase in G. roseum , by inserting a hygromycin resistance cassette into the coding sequence of the gene by means of Agrobacterium tumefaciens -mediated genetic transformation. The zes2 disruption mutants could not hydrolyze the lactone bond of zearalenone and were more sensitive to zearalenone. These data are consistent with a hypothesis that resorcylic acid lactones exemplified by zearalenone act to reduce growth competition by preventing competing fungi from colonizing substrates occupied by zearalenone producers and suggest that they may play a role in fungal defense against mycoparasites.