Honeysuckle has long been cultivated in East Asia for its flower buds, which are used in traditional medicine and valued for compounds such as chlorogenic acid, flavonoids, and iridoid glycosides. In production, delayed bud opening is a practical advantage because it gives growers more time to collect high-quality buds before full bloom. Yet the molecular switch that keeps some cultivars closed longer has remained unclear. Jasmonic acid is known to regulate plant development, stress responses, and flower opening, but its effects vary across species and tissues. Based on these challenges, in-depth research into how genome structure shapes hormone-controlled flower opening is needed.
A research team from Shandong University of Traditional Chinese Medicine reported (DOI: 10.1093/hr/uhag078) the findings in Horticulture Research on 3 March 2026. The article presents a genome-to-hormone explanation for delayed opening in 'Huajin 6'. The study combines PacBio long-read sequencing, high-throughput chromosome conformation capture (Hi-C), RNA sequencing, real-time quantitative polymerase chain reaction (RT-qPCR), hormone quantification, jasmonic acid (JA) treatment, and transgenic Arabidopsis thaliana assays to test the mechanism.
The team first built an 824.72-Mb chromosome-level genome for 'Huajin 6', with 98.46% of the assembly anchored to nine pseudochromosomes. Compared with other L. japonica genomes,
'Huajin 6'showed a notable contraction in the LOX gene family, especially the 9-LOX branch. It carried 35 LOX genes overall, compared with 44 in 'Sijihua'and 51 in 'Lj10107428'; the 9-LOX copy number fell to 11, compared with 20 and 21 in the two reference cultivars. This genomic pattern matched later biological signals. During the complete white stage, when 'Sijihua'begins to move toward opening, 'Huajin 6' showed weaker activation of JA-related genes and cell-wall modification genes. Weighted gene co-expression network analysis (WGCNA) also identified a JA-responsive module that was active in 'Sijihua'but muted in 'Huajin 6'. RT-qPCR confirmed that the genes LOX, allene oxide synthase (AOS), and allene oxide cyclase (AOC) were 3.8- to 5.2-fold lower than in 'Sijihua'at later stages. Hormone measurements showed that JA and methyl jasmonate (MeJA) were reduced 4.1-fold and 3.7-fold, respectively. When JA was applied externally, delayed buds opened rapidly, and Lonicera LOX genes increased jasmonate accumulation when expressed in A. thaliana.
The authors said the work reframes delayed flowering as a hormone-threshold problem rather than a simple calendar trait. They said a smaller LOX gene set appears to lower the plant's capacity to produce enough JA at the moment when buds normally open. In that model, 'Huajin 6'does not lose the ability to flower; instead, its floral transition is held below the jasmonate level needed to activate cell-wall loosening and bud expansion. This gives breeders a clearer, more direct molecular handle on a trait that has mostly been selected by field observation.
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References
DOI
10.1093/hr/uhag078
Original Source URL
https://doi.org/10.1093/hr/uhag078
Funding information
This work is supported by The Construction Engineering Special Fund of ‘Taishan Scholars’ of Shandong Province (tsqn202211135), Shandong Provincial Key R&D Program (Rural Revitalization Science and Technology Innovation Promotion Action Plan) project (2022TZXD0036), Shandong Provincial Modern Agricultural Industry Technology System Herbal Medicine Innovation Team Project (SDAIT-20).
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.