Genome-wide identification, transcriptional profiling, and miRNAbinding site analysis of the LBD gene family in the camphor tree

Jiaqi Zhang¹Luyang Shan¹Haoran Qi²Caihui Chen³Yongda Zhong³Meng Xu^1*

• ¹College of Forest Resources and Environment, Nanjing Forestry University, Nanjing, Jiangsu, China
• ²Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, Jiangsu Province, China
• ³Institute of Biology and Resources, Jiangxi Academy of Sciences, Nanchang City, Jiangxi Province, China

Cinnamomum camphora (Lauraceae), an evergreen arborescent species endemic to East Asian ecosystems, is ecologically and economically prized for three cardinal attributes: decayresistant xylem, aesthetic canopy architecture, and pharmacologically active terpenoid emissions. The plant-specific Lateral Organ Boundaries Domain (LBD) transcription factors mediate phylogenetically conserved developmental pathways governing lateral organogenesis and secondary metabolism across embryophytes. Despite multiple published C. camphora genome assemblies, functional characterization of LBD transcription factors in this species remains limited. We systematically identified 40 LBD genes through whole-genome analysis and characterized their structural features, evolutionary relationships, and expression patterns.Five are intron-free, while seven genes harbor two or more introns each. Detailed annotation of CcLBD promoter regions identified 33 cis-regulatory elements linked to hormone signaling and stress adaptation. Transcriptional dynamics of the 40 CcLBD genes were profiled across seven tissues of the camphor tree using short-read RNA-Seq, revealing that 22 genes were highly expressed in flowers and 12 were predominantly expressed in roots, suggesting potential roles in reproductive organ development and root formation in C. camphora. Phylogenetic analysis classified all CcLBD proteins into two clades, each harboring a conserved lateral organ boundaries (LOB) domain. Integrative omics analyses (small RNA-seq and degradome data) further implicated miR408 and miR2950c in post-transcriptional regulation of CcLBD5 via mRNA cleavage. These results establish a framework for the functional dissection of LBDmediated developmental and stress-response pathways in C. camphora.