Timing of gliotoxin biosynthesis in the fungal biological control agent Gliocladium virens (Trichoderma virens)

Gliocladium virens is a filamentous fungus formulated for the biological control of damping-off diseases of plants. Part of its antagonistic activity is due to its production of an epidithiodiketopiperazine antibiotic, gliotoxin. A relatively short period of biocontrol activity limits the use of this biocontrol agent in certain applications. This report examines the apparent transient accumulation of gliotoxin, a potential limitation in biocontrol activity. S-35 pulse labeling of gliotoxin indicated that G. virens strain G20-4VIB synthesizes gliotoxin only within a short 16-h period during replicative growth. An apparent lack of gliotoxin production in later growth phases was due to the cessation of synthesis rather than an increase in gliotoxin catabolism. Media-transfer experiments indicated that cessation of gliotoxin synthesis could not be explained by gliotoxin feedback inhibition, a diffusible inhibitor, or changing the nutritional status of the medium over a 2-h response time. These results demonstrate that the regulation of gliotoxin biosynthesis is a major determinant in the kinetics of gliotoxin appearance and focuses the need for further study on the regulation of gene expression.