Critical thresholds of 1-Octen-3-ol shape inter-species Aspergillus interactions modulating the growth and secondary metabolism

In fungi, contactless interactions are mediated via the exchange of volatile organic compounds (VOCs). As these pair-wise interactions are fundamental to complex ecosystem, we examined the effects of inter-species VOCs trade-offs in Aspergillus flavus development. First, we exposed A. flavus to the A. oryzae volatilome (Treatment-1) with highest relative abundance of 1-Octen-3-ol (similar to 4.53 folds) among the C-8 VOCs. Further, we examined the effects of gradient titers of 1- Octen-3-ol (Treatment-2: 100-400 ppm/day) in a range that elicits natural interactions. On 7-day, VOC-treated A. flavus displayed significantly reduced growth and sclerotial counts (p<0.01) coupled with higher conidial density (T2(100-200 ppm/day), p<0.01) and alpha-amylase secretion (T2(200 ppm/day), p<0.01), compared to the untreated sets. Similar phenotypic trends except for alpha-amylases were evident for 9-day incubated A. flavus in T2. The corresponding metabolomics data displayed a clustered pattern of secondary metabolite profiles for VOC-treated A. flavus (PC1-18.03%; PC2-10.67%). Notably, a higher relative abundance of aflatoxin B1 with lower levels of most anthraquinones, indole-terpenoids, and oxylipins was evident in VOC-treated A. flavus. The observed correlations among the VOC-treatments, phenotypes, and altered metabolomes altogether suggest that the distant exposure to the gradient titers of 1-Octen-3-ol elicits an attenuated developmental response in A. flavus characterized by heightened virulence.