Analysis of the fumonisin production in the Fusarium verticillioides-maize interaction by using a Green Fluorescent Protein-expressing transgenic isolate under control of the FUM1 promoter

Fumonisins are a family of mycotoxins produced by Gibberella moniliformis (anamorph Fusarium moniliforme) that contaminate maize and maize-based products, notably those produced in Northern Italy, and cause great concern for human and animal health. We report on the characterization of a Fusarium moniliforme collection representative of the Piedmont region (NW Italy) and its subgrouping in F. verticillioides and F. proliferatum strains by morphological and molecular analyses. Isolates were characterized with regard to genetic variability by VCG analysis, ITS-RFLP and AFLP. Toxigenicity was assessed directly by HPLC analysis of FB1 and FB2 production in vitro. Amplificability of FUM1 (the gene encoding the key enzyme into the fumonisin pathway) and of its putative promoter region (pFUM1) was checked by 3 pairs of primers. Amplification was associated with fumonisin production in most isolates, with few interesting exceptions. To study the genetic and environmental factors linked to fumonisin production, we amplified pFUM1 (about 1000 bp upstream of the start codon) from a toxigenic F. verticillioides strain of our collection, and used it to generate transgenic F. verticillioides strains expressing the pFUM1::GFP cassette. These are being tested for pFUM1 activity upon maize infection and in fumonisin-inducing and non-inducing conditions, to assess whether toxins are associated to early plant colonization, and/or other life stages of the fungus.