Molecular and genetic studies of Fusarium trichothecene biosynthesis: toward understanding the transcriptional regulatory mechanisms of trichothecene (Tri) genes

Abstract

  To gain insights into the regulatory mechanism of trichothecene biosynthesis, I worked on molecular genetic studies of Fusarium graminearum in RIKEN and Nagoya University. First, Aspergillus nidulans promoters with different levels of transcription were identified and characterized in F. gramienarum. Second, subcellular localization of Tri6p, a zinc finger protein essential for trichothecene (Tri) gene transcription, was analyzed by using these promoters. When the predicted nuclear localization sequence (NLS) of Tri6 was fused to the EGFP (enhanced green fluorescence protein) gene and transcribed under the control of a strong A. nidulans TEF1α promoter, the EGFP green fluorescence was clearly observed in the nucleus, demonstrating the functionality of the nuclear localization signal. Third, the role of sucrose as an inducer, but not as the carbon source of the medium, in trichothecene production was unambiguously demonstrated. Based on the mode of actions of sucrose and other chemicals that modulate trichothecene production, a new regulatory model of Tri6 expression is now being proposed. Further investigations with molecular and mechanisms of genetic approaches using these tools will clarify the trichothecene biosynthesis regulation.