A HD-ZIP Transcription Factor Regulates Flower Senescence via Ethylene and ABA Cross-talks in Petunia

Flower senescence is a genetically controlled developmental process. Transcription factors play an important role in plant growth and development.  We found that a homeodomain-leucine zipper transcription factor, PhHD-Zip, is up-regulated during petunia flower senescence from transcriptome analysis. Virus-induced gene silencing of PhHD-Zip extended flower life by 20% both in unpollinated and pollinated flowers. Silencing PhHD-Zip also dramatically reduced ethylene production and the abundance of transcripts of genes involved in ethylene (ACS, ACO), ABA (NCED) biosynthesis as well as senescence-related marker genes (SAG12, SAG29). On the other hand, over-expression of PhHD-Zip accelerated petunia flower senescence accompanying with enhanced expression of ethylene biosynthesis-related genes. Furthermore, PhHD-Zip transcript abundance in petunia flowers was increased by application of hormones (ethylene, ABA) and abiotic stresses (dehydration, NaCl and cold). Our results suggest that PhHD-Zip plays an important role in regulating petunia flower senescence through cross-talk of ethylene and ABA.