Abstract
AAL-toxin is a pathogenicity factor of Alternaria alternata f. sp. lycopersici. Little is known about the signaling pathway of AAL-toxin leading to programmed cell death. To investigate candidate genes involved in AAL-toxin-induced cell death, we employed virus-induced gene silencing (VIGS) and Nicotiana umbratica that is sensitive to the AAL-toxin. We showed that ethylene signaling pathway plays a pivotal role in AAL-toxin-induced cell death and identified NuERF4, which is AP2/ERF transcription factor, as a mediator for AAL-toxin-induced cell death. Overexpression of NuERF4 did not induce cell death, however, accelerated AAL-toxin-induced cell death. Moreover, disease symptom by A. alternata f. sp. lycopersici was more severe by the NuERF4 overexpression. We also indicated that NuERF4 is a transcriptional activator. These results suggest that the NuERF4 positively regulates some factors involved in AAL-toxin-induced cell death. At present, we are trying to hunt the targets of NuERF4 using PCR-select cDNA subtraction method to elucidate the downstream signaling of the NuERF4.
