|VILLANI, ALESSANDRA - National Research Council - Italy|
|SUSCA, ANTONELLA - National Research Council - Italy|
|MORETTI, ANTONIO - National Research Council - Italy|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/19/2017
Publication Date: N/A
Technical Abstract: Trichothecenes are among the mycotoxins of greatest concern to food and feed safety and are produced by at least two lineages of Fusarium: F. sambucinum (FSAMSC) and F. incarnatum-equiseti (FIESC) species complexes. Trichothecene biosynthesis begins with the formation of a cyclic sesquiterpene followed by up to eight oxygenation and four acylation reactions. Most trichothecene biosynthetic genes (TRI) are co-regulated and located in a cluster. All Fusarium TRI cluster homologs characterized to date include two regulatory genes that encode a C2H2 zinc finger (TRI6) and a fungal transcription factor domain (TRI10). Functional analysis of FSAMSC members indicate that TRI6 regulates expression of structural genes in the TRI cluster, while TRI10 regulates TRI6 expression. Here, we characterized a novel gene, TRI21, located in the TRI cluster of FIESC but not FSAMSC, which encodes a Zn2Cys6 transcription factor. Gene deletion and precursor feeding analyses with a FIESC isolate indicate that TRI21 is required for expression of two TRI cluster genes (TRI11 and TRI13) responsible for two later oxygenation reactions, but not for expression of other cluster genes. In contrast, TRI6 is required for expression of genes required for earlier and some later steps in trichothecene biosynthesis but not for TRI11 and TRI13 expression. These results indicate fundamental differences in the regulation of the TRI cluster in FIESC and FSAMSC. Furthermore, the presence of a pseudogenized TRI21 in some members of FSAMSC indicates that the evolution of TRI cluster regulation in FSAMC has included loss of TRI21 and expansion of the role of TRI6 in trichothecene biosynthesis.