A petunia transcription factor, , regulates flower senescence by modulating gibberellin biosynthesis.

Flower senescence is commonly enhanced by the endogenous hormone ethylene and suppressed by the gibberellins (GAs) in plants. However, the detailed mechanisms for the antagonism of these hormones during flower senescence remain elusive. In this study, we characterized one up-regulated gene , belonging to the basic leucine zipper transcription factor family, in senescing petals of petunia (). Exogenous treatments with ethylene and GA provoked a dramatic increase in transcripts. Compared with wild-type plants, -RNAi transgenic petunia plants exhibited shortened flower longevity, while overexpression of resulted in delayed flower senescence Transcript abundances of two senescence-related genes and were higher in -silenced plants but lower in -overexpressing plants. Silencing and overexpression of affected expression levels of a few genes involved in the GA biosynthesis and signaling pathways, as well as accumulation levels of bioactive GAs GA and GA. Application of GA restored the accelerated petal senescence to normal levels in -RNAi transgenic petunia lines, and reduced ethylene release and transcription of three ethylene biosynthetic genes , , and . Moreover, PhOBF1 was observed to specifically bind to the promoter containing a G-box motif. Transient silencing of in petunia plants through tobacco rattle virus-based virus-induced gene silencing method led to accelerated corolla senescence. Our results suggest that PhOBF1 functions as a negative regulator of ethylene-mediated flower senescence by modulating the GA production.