Biogeography and relatedness of Nodulisporium strains producing nodulisporic acid

Nodulisporic acid, a novel indole terpene with insecticidal properties, was first isolated from a fermentation broth of an endophytic Nodulisporium sp . Following an extensive culture screening effort, fermentations of 12 othe r strains of Nodulisporium also yielded nodulisporic acid. These strains ca me from a variety of environmental substrata collected from seven tropical regions in four continents. Cultural characteristics and microscopic featur es show that all the nodulisporic acid-producing Nodulisporium strains are morphologically very similar. AP-PCR and sequencing of the rDNA region cons isting of the two internal transcribed spacers and the 5.8S gene revealed t hat the isolates were distributed into three groups, according to the lengt h of the ITS1. The two groups with the longest sequences were not distingui shable, based on nucleotide divergence data calculated from the common regi on of ITS1. The group of isolates with shorter sequences showed lower homol ogy with the other groups in the ITS1 region, but those strains could not b e distinguished from the other groups, according to ITS2 sequences. These d ata suggest that the nodulisporic acid producing isolates are very closely related and may constitute a single species, although divided into populati ons showing some degree of genetic differentiation. Comparison of the seque nces obtained in this work with sequences from other xylariaceous fungi wit h Nodulisporium-type anamorphs failed in determining the teleomorph of the nodulisporic acid-producing Nodulisporium species. However, it revealed tha t these isolates constitute a monophyletic group, clearly different from ot her tropical and temperate isolates of Nodulisporium not able to produce no dulisporic acid.