Functional Role of Gene, a bZIP Transcription Factor within the OTA Gene Cluster.

is the principal fungal species responsible for ochratoxin A (OTA) contamination of grapes and derived products in the main viticultural regions worldwide. In recent years, co-expressed genes representing a putative-OTA gene cluster were identified, and the deletion of a few of them allowed the partial elucidation of the biosynthetic pathway in the fungus. In the putative OTA-gene cluster is additionally present a bZIP transcription factor (), and with this work, Δ strains were generated to study its functional role. According to phylogenetic analysis, the gene is conserved in the OTA-producing fungi. A transcription factor binding motif (TFBM) homolog, associated with bZIP transcription factors was present in the OTA-gene cluster no-coding regions. deletion results in the loss of OTA and the intermediates OTB and OTβ. Additionally, in Δ strains, a down-regulation of , , , and genes was observed compared to wild type (WT). These results provide evidence of the direct involvement of the gene in the OTA biosynthetic pathway by regulating the involved genes. The loss of OTA biosynthesis ability does not affect fungal development as demonstrated by the comparison of Δ strains and WT strains in terms of vegetative growth and asexual sporulation on three different media. Finally, no statistically significant differences in virulence were observed among Δ strains and WT strains on artificially inoculated grape berries, demonstrating that OTA is not required by for the pathogenicity process.