Abstract
A group of ethylene response factors (ERFs) clustered at the NIC2 regulatory locus regulates nicotine biosynthesis in tobacco. Overexpression, suppression, and dominant repression experiments of the NIC2-locus ERFs using transgenic tobacco roots showed their critical roles as mater regulators for the biosynthesis, and also both functional redundancy and divergence among the ERF genes. These transcription factors recognized a GCC-box element in the promoter of a nicotine pathway gene and specifically activated all known structural genes in the pathway. The NIC2-locus ERF genes are expressed in the root and up-regulated by jasmonate with kinetics that are distinct among the members. Thus, gene duplication events generated a cluster of highly homologous transcription factor genes with transcriptional and functional diversity. We will discuss how these and other factors are involved in the jasmonate-mediated up-regulation of nicotine biosynthesis, and possible involvement of this subclass of the jasmonate-responsive ERF genes in various bioactive alkaloids.
