Deletion of the trichodiene synthase gene of Fusarium venenatum: two systems for repeated gene deletions.

The trichodiene synthase (tri5) gene of Fusarium venenatum was cloned from a genomic library. Vectors were created in which the tri5 coding sequence was replaced with the Neurospora crassa nitrate reductase (nit3) gene and with the Aspergillus nidulans acetamidase (amdS) gene flanked by direct repeats. The first vector was utilized to transform a nitrate reductase (niaD) mutant of F. venenatum to prototrophy, and the second vector was utilized to confer acetamide utilization to the wild-type strain. Several of the transformants lost the capacity to produce the trichothecene diacetoxyscirpenol and were shown by hybridization analysis to have gene replacements at the tri5 locus. The nit3 gene was removed by retransformation with a tri5 deletion fragment and selection on chlorate. The amdS gene was shown to excise spontaneously via the flanking direct repeats when spores were plated onto fluoroacetamide.

Species-specific primers resolve members of Fusarium section Fusarium. Taxonomic status of the edible "Quorn" fungus reevaluated.

Sixty-seven authentic isolates, representing six species from Fusarium section Fusarium (= section Discolor) were subjected to random amplified polymorphic DNA (RAPD) analysis and polymerase chain reaction using species-specific primers. Remarkably uniform RAPD banding patterns were obtained intraspecifically, irrespective of the geographical origin of the isolates or the host/substratum from which they were isolated. Isolates were also assessed for colony characteristics when grown on a defined minimal medium. The Quorn strain (ATCC 20334; previously considered to be F. graminearum) matched the F. venenatum strains exclusively in RAPD profile. In addition, equivalently sized DNA fragments amplified from ATCC 20334 and two authentic F. venenatum strains were identical with respect to DNA sequence. Our molecular and morphological data support the identification of the Quorn strain as F. venenatum Nirenberg (= F. sambucinum Fuckel sensu lato).

Fusarium graminearum A 3/5 as a novel host for heterologous protein production.

We describe a novel fungal expression system which utilizes the Quorn myco-protein fungus Fusarium graminearum A 3/5. A transformation system was developed for F. graminearum and was used to introduce the coding and regulatory regions of a trypsin gene from Fusarium oxysporum. The protein was efficiently expressed, processed and secreted by the recombinant host strain. In addition, the promoter and terminator of the F. oxysporum trypsin gene have been successfully utilized to drive the expression of a cellulase gene from Scytalidium thermophilum and a lipase gene from Thermomyces lanuginosus in F. graminearum.