The mystery of trichothecene antibiotics in Baccharis species.

The Brazilian higher plant Baccharis coridifolia has been shown to synthesize de novo a series of highly toxic macrocyclic trichothecene antibiotics heretofore found to be produced only by fungi. These compounds are produced only by female plants that have undergone pollination. Neither the male nor female plant is sensitive to the toxic effects of trichothecenes, whereas North American Baccharis species are. The macrocyclic trichothecenes found in B. coridifolia are the same as those produced by Myrothecium fungi, and it is suggested that the plant has acquired the toxin-producing genes from this fungus.