A new family of zinc finger proteins in petunia: structure, DNA sequence recognition, and floral organ-specific expression.

We have previously cloned a gene for a zinc finger protein (EPF1) that is expressed specifically in petals and interacts with the promoter region of the 5-enolpyruvylshikimate-3-phosphate synthase gene in petunia. In an attempt to isolate genes encoding additional factors that interact with this promoter, we cloned four novel genes encoding zinc finger proteins (EPF2-5a, EPF2-5b, EPF2-4, and EPF2-7). Sequence analyses revealed that overall similarity between the EPF1 and the EPF2 protein family, except in the zinc finger motifs and the basic amino acid cluster, was very low, suggesting that the two groups belong to different subfamilies. DNA binding specificities of EPF1, EPF2-5, and EPF2-4 were very similar, as expected from the conserved zinc finger motifs. However, EPF2-7 showed no binding to the probes tested in spite of having the conserved motifs. DNA binding studies using a series of spacing mutant probes suggested a binding mechanism in which the EPF proteins recognize spacings in target DNA. RNA gel blot analyses and histochemical analyses with a promoter and beta-glucuronidase fusion revealed that expression of the EPF2-5 gene (EPF2-5) was petal and stamen specific. Expression of the EPF2-7 gene (EPF2-7) was sepal and petal specific and localized in vascular tissues. The preferential expression in two adjacent floral organs raises the possibility that these genes are downstream transcription factors of floral homeotic genes.