The mode of phytotoxic action of trichothecenes during plant- Fusarium interaction; our approach to detoxification of trichothecenes in cereals.

Abstract

Phytopathogenic fungi Fusarium species are etiological agents of Fusarium head blight (FHB) and produce trichothecene mycotoxins such as deoxynivalenol (DON) and nivalenol (NIV) in cereals especially barley and wheat. Trichothecenes inhibit the protein synthesis in eukaryotic ribosomes. Therefore, trichothecene-contaminated cereals often cause foodborne illness such as immunosuprression, vomiting, and diarrhea in human and livestocks. Trichothecenes are also phytotoxins and act as effectors to promote infection in host plants. Based on visible disease symptoms, we selected 15 FHB-resistant lines of barley. When these resistant lines and susceptible controls were inoculated with conidia of F. asiaticum, the mycotoxin (NIV) contaminations of resistant two lines were less than half of those of susceptible controls. Furthermore, we performed comparative analysis of global gene expression profiles between these FHB-resistant (low NIV accumulation) lines vs. susceptible controls. A number of genes including the glutathione S-transferase (HvGST13) and glutathione reductase (HvGR2) were specifically up-regulated in the FHB-resistant lines. It is likely that these two genes are involved in the detoxification of NIV by NIV-GSH conjugation in barley. Therefore, we are studying these genes as candidates of trichothecene-detoxifing genes. This study may contributes to the understanding molecular mechanism of trichothecene detoxification in cereals.