Production of sterigmatocystin (ST) in Aspergillus nidulans involves the ST biosynthetic gene cluster, which has been considered to comprise 26 genes. However, functions of several genes within this cluster remain unclear. In this study, we investigated the role of the stcX gene in ST biosynthesis. As the open reading frame of stcX has been undefined, we deleted three putative genes adjacent to stcW simultaneously. Deletion of the region did not significantly impact growth rate across various growth conditions compared to the control strain. Chemical analyses revealed no significant change in ST production in the deletion strain compared to the control. Furthermore, the three transcripts were largely undetectable during ST biosynthesis, and the expression of other ST cluster genes was unaffected by the deletion. Our results suggest that these genes are not essential for ST biosynthesis in A. nidulans, indicating that the cluster should be delineated to exclude stcX.
Yamada et al. (Thu,) studied this question.