A petunia transcription factor, PhOBF1, regulates flower senescence by modulating gibberellin biosynthesis

Abstract

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 PhOBF1, belonging to the basic leucine zipper transcription factor family, in senescing petals of petunia (Petunia hybrida). Exogenous treatments with ethylene and GA₃ provoked a dramatic increase in PhOBF1 transcripts. Compared with wild-type plants, PhOBF1-RNAi transgenic petunia plants exhibited shortened flower longevity, while overexpression of PhOBF1 resulted in delayed flower senescence. Transcript abundances of two senescence-related genes PhSAG12 and PhSAG29 were higher in PhOBF1-silenced plants but lower in PhOBF1-overexpressing plants. Silencing and overexpression of PhOBF1 affected expression levels of a few genes involved in the GA biosynthesis and signaling pathways, as well as accumulation levels of bioactive GAs GA₁ and GA₃. Application of GA₃ restored the accelerated petal senescence to normal levels in PhOBF1-RNAi transgenic petunia lines, and reduced ethylene release and transcription of three ethylene biosynthetic genes PhACO1, PhACS1, and PhACS2. Moreover, PhOBF1 was observed to specifically bind to the PhGA20ox3 promoter containing a G-box motif. Transient silencing of PhGA20ox3 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.

Acknowledgements

We thank Houhua Li for offering the pHIS2 and pGADT7-Rec vectors. We are grateful to Jiaxin Meng for technique help in dual luciferase assay. We are appreciative of Xiaokun Liu’s kind favor for apparatus operation. This study was funded by the National Natural Science Foundation of China (Grant no. 32271953 and 31801895), Postdoctoral Special Funding Project of China (Grant no. 2019T120958), and the Basic Scientific Research Expense of Northwest A&F University (Grant no. Z1090322159).

Author contributions

D.S. and X.J. conceived and designed the experiments. X.J., Z.X., Y.Y., M.W., X.L., and J.L. conducted the experiments. C.J. provided the materials. M.W., X.L., and J.L. prepared the reagents. X.J., Z.X., Y.Z., L.N., and D.S. analysed the experimental data. X.J. and D.S. wrote the original paper. D.S., C.J., L.N., and Y.Z. revised the manuscript.

Data availability

All data supporting the conclusions of this work are present in the paper or its Supplementary material files.

Conflict of interest

The authors declare that they have no conflict of interest.

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