Plants lack specialized cells to combat invading pathogens, necessitating that every plant cell must be capable of mounting an effective defence response to prevent disease. The perception of a pathogen by a plant cell leads to rapid activation of defence responses that induce numerous signal transduction pathways. This in turn leads to massive changes in gene expression. In recent years, key players in these signal transduction pathways have been identified. They include the disease resistance genes, which often confer resistance to specific pathogens; protein kinases; defence regulatory proteins; transcription factors; and small molecules able to activate defence pathways. However, despite the progresses in the identification of key molecules involved in defence response pathways, the function of these molecules is still poorly characterized.

We have determined the structure of a key plant defence transcription factor that activates plant defences. The structure represents a novel protein fold that belongs to a newly found protein family, ubiquitous yet specific to plants, and has a new ssDNA binding surface. The fourfold symmetry of the quaternary structure succinctly explains its binding preference for palindromic DNA sequences and mode of transcriptional activation. Our structure made the cover of Nature Structural Biology in July 2002. Our long-term goal is to improve activator binding to its cognate DNA sequence in order to enhance the plant defence response to pathogens.