The ethylene-responsive factor OfERF4c interacts with OfVFP4 to regulate petal senescence in Osmanthusfragrans

Abstract

Flowering duration critically determines the ornamental and economic value of Osmanthus fragrans, yet the molecular mechanisms regulating petal senescence remain incompletely understood. Ethylene is a major promoter of petal senescence, acting through ethylene-responsive factors (ERFs), which function as key transcriptional regulators downstream of ethylene signaling. In this study, integrated transcriptomic and quantitative expression analyses revealed that OfERF4c is strongly upregulated after full flowering stage, implicating it in senescence progression. The results of subcellular localization demonstrated that the transcription factor resides within the nucleus. Functional characterization showed that heterologous overexpression of OfERF4c in Nicotiana tabacum significantly shortened flower lifespan. Consistently, transient overexpression of OfERF4c in O. fragrans petals upregulated senescence-associated genes, while virus-induced gene silencing (VIGS) of OfERF4c led to their significant downregulation and delayed petal senescence. Furthermore, OfERF4c-overexpressing petals exhibited elevated levels of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂), coupled with reduced catalase (CAT) activity, indicating enhanced oxidative stress. Yeast one-hybrid and dual-luciferase reporter assays demonstrated that the transcription factor OfVFP4 directly binds the OfERF4c promoter to activate its expression. Given that OfVFP4 belongs to the GeBP-like family and Arabidopsis GeBP proteins are implicated in cytokinin signaling modulation, we hypothesize that the OfVFP4-mediated regulation of OfERF4c may potentially link to hormonal crosstalk during petal senescence, which warrants further investigation. This work establishes OfERF4c as a positive regulator of petal senescence and provides new insights into the transcriptional network governing floral longevity in O. fragrans.

Keywords: OfERF4c; OfVFP4; Osmanthus fragrans; Petal senescence; Transcriptional regulation.