Autoregulation of ZEB2 expression for zearalenone production in Fusarium graminearum

Abstract

SummarySeveral Fusarium species produce the polyketide mycotoxin zearalenone (ZEA), a causative agent of hyperestrogenic syndrome in animals that is often found in F. graminearum-infected cereals in temperate regions. The ZEA biosynthetic cluster genes PKS4, PKS13, ZEB1 and ZEB2 encode a reducing polyketide synthase, a non-reducing polyketide synthase, an isoamyl alcohol oxidase and a transcription factor respectively. In this study, the production of two isoforms (ZEB2L and ZEB2S) from the ZEB2 gene in F. graminearum via an alternative promoter was characterized. ZEB2L contains a basic leucine zipper (bZIP) DNA-binding domain at the N-terminus, whereas ZEB2S is an N-terminally truncated form of ZEB2L that lacks the bZIP domain. Interestingly, ZEA triggers the induction of both ZEB2L and ZEB2S transcription. ZEB2L and ZEB2S interact with each other to form a heterodimer that regulates ZEA production by reducing the binding affinity of ZEB2L for the ZEB2L gene promoter. Our study provides insight into the autoregulation of ZEB2 expression by alternative promoter usage and a feedback loop during ZEA production; this regulatory mechanism is similar to that observed in higher eukaryotes.

Biosynthetic mechanism and regulation of zearalenone in <i>Fusarium graminearum</i>

“…These results led us to examine the different roles of ZEB2 complexes as transcriptional regulators. The direct binding of ZEB2L to the promoter regions of the ZEA biosynthetic cluster genes, PKS4, PKS13, ZEB1, and ZEB2, was confirmed using an electrophoretic mobility shift assay (EMSA) 17) .…”

“…ZEB2L strongly interacted with both ZEB2L and ZEB2S, and two interaction domains of ZEB2 were found to be required for ZEB2L-ZEB2L, ZEB2L-ZEB2S, and ZEB2S-ZEB2S dimerizations 17) . These results led us to examine the different roles of ZEB2 complexes as transcriptional regulators.…”

“…3B). Likewise, ZEB2L-ZEB2S interactions in the nuclei inhibited ZEB2L function for ZEA production 17) .…”

“…Two ZEB2 transcripts, ZEB2L and ZEB2S, were first found via northern blot analyses ( Fig. 2A) 17) . We performed cDNA sequencing of the ZEB2 transcript and confirmed that ZEB2L contains a bZIP DNA-binding domain at the N-terminus, whereas ZEB2S is an N-terminally truncated form of ZEB2L that lacks the bZIP domain (Fig.…”

“…An illustration of the transformed fungal construct used is included above each blot. These data came from a previous report with slight modifications 17) .…”