Genomic contraction of the LOX gene family limits jasmonic acid biosynthesis and contributes to delayed flower bud opening in honeysuckle ( Lonicera japonica)

Abstract

The delayed flower bud opening of Lonicera japonica ‘Huajin 6’ extends its harvest window and enhances agricultural value, yet the underlying molecular basis remains unclear. Here, we assembled a chromosome-level genome of ‘Huajin 6’ using PacBio sequencing and high-throughput chromosome conformation capture scaffolding (824.72 Mb, scaffold N50 = 91.2 Mb). Comparative genomic analyses revealed a subfamily-specific contraction of lipoxygenase ( LOX) genes, particularly within the 9-LOX clade, which is associated with a reduced jasmonate biosynthetic capacity during floral development. Transcriptomic and hormone profiling showed coordinated suppression of jasmonic acid (JA) biosynthesis-related genes and a marked reduction of JA and its bioactive derivatives during the transition from the complete white stage to flower opening. A JA-responsive co-expression module enriched in cell wall modification genes exhibited attenuated activation in ‘Huajin 6’. Functional assays further demonstrated that exogenous JA restored timely flower bud opening in both ‘Huajin 6’ and L. macranthoides, while heterologous expression of Lonicera LOX genes enhanced jasmonate accumulation in Arabidopsis. Together, these findings are consistent with a jasmonate threshold model in which LOX gene contraction constrains JA accumulation during floral transition, contributing to delayed flower bud opening and highlighting how genome structural variation influences hormone-dependent flowering dynamics.

Acknowledgements

We thank Professor Yin Xiaojian from the Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences for providing us with the L. macranthoides genomic 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).

Author contributions

L.Z. participated in the conceptualization, investigation, methodology, writing-original draft, designed and conducted experiments, and drafted the manuscript. L.C. and H.C. participated in the normal analysis, data curation, validation, performed component extraction, chemical analysis, and result interpretation. Z.L., L.J., H.L., Z.G., P.S., L.R., and L.C. participated in the resources, investigation. collected honeysuckle germplasms and established the germplasm repository. Z.Y., L.J., and P.G. participated in the writing-review and editing, supervision, project administration, revised the manuscript and oversaw research coordination. All authors read and approved the final manuscript.

Data availability

All the relevant data supporting the findings of this study are available in the paper and supplementary data. The sequence data in this study can be found in the National Genomics Data Center under accession number PRJCA041333.

Conflicts of interest statement

The authors declare that they have no conflicts of interest.

Supplementary material

Supplementary material is available at Horticulture Research online.

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