Abstract
Phytopathogenic fungus capable of producing trichothecenes can be found throughout the world, and include certain species of Fusarium. Trichothecenes has a sesquiterpenoid ring structure, and can be classified according to the presence or absence of characteristic functional groups.
Type A trichothecenes, such as T-2 toxin, caused rapid and prolonged activation of MAPKs, and triggered the cell death by activation of an elicitor-like signaling pathway in Arabidopsis. However, a MAP kinase cascade in the response to trichothecenes is unknown. Novel MAPKKK (MKD1) was identified as a subunit of AtNFXL1 protein complex. We had revealed that AtNFXL1 functions as a negative regulator of the trichothecene-induced defense response. The mkd1 mutant enhanced susceptibility to Fusarium sporotrichioides compared with wild type. Furthermore, accumulation of T-2 toxin was increased in mkd1 mutant. The MKD1 gene is ubiquitously expressed in all organs examined, and highly expressed in stomata and vascular bundles. In gel kinase assays showed that the activation of MPK3 and MPK6 in mkd1 mutant by T-2 toxin was decreased compared with wild type.
