Researchers uncover temperature-sensitive genes controlling osmanthus bloom
image: Proposed working model of OfWRKY17-OfC3H49 responding to ambient temperature regulates flowering by inhibiting OfSOC1B expression in Osmanthus fragrans.
Credit: Horticulture Research
Flowering is a key developmental milestone for plants, directly influencing reproduction and ornamental value. In Osmanthus fragrans, high ambient temperatures are known to delay or even block flowering, but the molecular mechanism has been unclear. Researchers have now identified a temperature-responsive regulatory module composed of OfWRKY17 and OfC3H49, which acts to suppress the expression of OfSOC1B, a key flowering integrator. This repression significantly delays the onset of flowering under elevated temperatures. The discovery not only advances fundamental knowledge of how temperature shapes plant development but also opens new avenues for breeding strategies to improve ornamental performance and stability of flowering under climate change.
The timing of flowering is tightly coordinated by genetic pathways and environmental cues, with ambient temperature acting as one of the most critical factors. While in some species such as Arabidopsis thaliana warmer temperatures accelerate flowering, in others, including Osmanthus fragrans, elevated temperatures hinder floral transition. Previous studies suggested that zinc finger proteins and WRKY transcription factors participate in stress and developmental responses, but their precise roles in temperature-regulated flowering remained unresolved. The limited understanding of this mechanism restricts horticultural improvement of osmanthus, a prized ornamental species in East Asia. Due to these challenges, there is a need for deeper research on the molecular regulation of temperature-sensitive flowering.
A research team from Zhejiang Agriculture and Forestry University has published (DOI: 10.1093/hr/uhae273) new findings in Horticulture Research (September 24, 2024), revealing the molecular mechanism by which high ambient temperature inhibits flowering in O. fragrans. The study demonstrates that the transcription factor OfWRKY17 directly activates OfC3H49, which in turn suppresses OfSOC1B, thereby delaying flowering. These results provide fresh insights into how ornamental plants integrate temperature signals into their flowering pathways and highlight potential strategies for molecular breeding to counteract climate-related flowering delays.
The study began by exposing O. fragrans cv. “Sijigui” to different temperatures. At 19 °C, flower buds differentiated and reached stage V within 72 days, whereas at 25 °C, floral initiation was completely blocked, with buds remaining vegetative. Transcriptome analysis revealed that OfC3H49, a CCCH-type zinc finger protein, was strongly induced under high temperature and acted as a transcriptional repressor. Functional assays in Arabidopsis and osmanthus calli confirmed that overexpression of OfC3H49 delayed flowering and suppressed flowering-related genes, especially OfSOC1B. Yeast one-hybrid, EMSA, and dual-luciferase assays showed that OfC3H49 directly binds to the OfSOC1B promoter to inhibit its expression. Further upstream analysis identified OfWRKY17 as a direct activator of OfC3H49. Expression of OfWRKY17 was induced by high temperature, and its overexpression in Arabidopsis and osmanthus calli also delayed flowering by upregulating OfC3H49. Together, these results establish a regulatory cascade—OfWRKY17–OfC3H49–OfSOC1B—that acts as a brake on flowering under elevated temperature. This provides the first clear mechanistic evidence for how high temperature suppresses flowering in woody ornamentals.
“Understanding the genetic networks behind temperature-sensitive flowering is crucial in the context of climate change,” said lead author Dr. Bin Dong. “Our discovery of the OfWRKY17–OfC3H49 module provides a concrete molecular explanation for why sweet osmanthus often fails to bloom in hot summers. More importantly, this knowledge equips breeders with gene-level targets to manipulate flowering time. By fine-tuning this pathway, we may develop osmanthus cultivars that maintain consistent flowering performance across variable climates, ensuring both ecological adaptation and commercial value.”
The identification of the OfWRKY17–OfC3H49–OfSOC1B regulatory module has significant implications for horticultural breeding and climate resilience. By modulating the expression or activity of these genes, breeders could potentially develop new O. fragrans varieties that flower reliably despite high summer temperatures. Beyond ornamental horticulture, this work also contributes to the broader understanding of how woody perennials integrate environmental cues into reproductive development. As global temperatures rise, such mechanistic insights will be vital for securing flowering stability, ecological function, and agricultural productivity across diverse plant species, supporting both biodiversity conservation and the ornamental plant industry.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhae273
Funding information
This work was supported by the National Natural Science Foundation of China (Grant Nos. 31902057 and 32072615), Zhejiang Provincial Natural Science Foundation of China (Grant No. LQ19C160012), and the key research and development program of Zhejiang Province (Grant No. 2021C02071).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.