Cinnamomum camphora is a traditional aromatic plant used to produce linalool and borneol flavors in southern China; however, its leaves also contain many other unutilized essential oils. Herein, we report geographic relationships for the yield and compositional diversity of C. camphora essential oils. The essential oils of 974 individual trees from 35 populations in 13 provinces were extracted by hydrodistillation and analyzed qualitatively and quantitatively by gas chromatography-mass spectrometry and gas chromatography-flame ionization detection, respectively. Oil yields ranged from 0.01% to 3.46%, with a significantly positive correlation with latitude and a significantly negative correlation with longitude. In total, 41 compounds were identified, including 15 monoterpenoids, 24 sesquiterpenoids, and two phenylpropanoids. Essential oil compositions varied significantly among individuals and could be categorized into various chemotypes. The six main chemotypes were eucalyptol, nerolidol, camphor, linalool, selina, and mixed types. The other 17 individual plants were chemotypically rare and exhibited high levels of methyl isoeugenol, methyl eugenol, δ-selinene, or borneol. Eucalyptol-type plants had the highest average oil yield of 1.64%, followed in decreasing order by linalool-, camphor-, mixed-, selina-, and nerolidol-type plants. In addition, the five main compounds exhibited a clear geographic gradient. Eucalyptol and linalool showed a significantly positive correlation with latitude, while selina-6-en-4-ol was significantly and negatively correlated with latitude. trans-Nerolidol and selina-6-en-4-ol showed significantly positive correlations with longitude, whereas camphor was significantly and negatively correlated with longitude. Canonical correspondence analysis indicated that environmental factors could strong effect the oil yield and essential oil profile of C. camphora.

Cinnamomum plants are rich in natural essential oils, which are widely used as materials in the fragrance, insecticidal, antibacterial agent, pharmaceutical, and food industries; however, few studies have investigated the essential oil components of Cinnamomum bodinieri. Therefore, this study investigated the diversity of essential oils from the leaves of 885 individual C. bodinieri plants across 32 populations in five provinces. Essential oils were extracted by hydrodistillation, and then qualitative and quantitative analyses of the compounds were performed by GC-MS and GC-FID. A total of 87 chemical constituents were identified in the essential oils, including 33 monoterpenes, 48 sesquiterpenes, and six other compounds. The average oil yield was 0.75%, and individual oil yields ranged from 0.01% to 4.28%. A total of 16 chemotypes were classified according to variations in the essential oil chemical constituents of C. bodinieri, among which the camphor-type, citral-type, and eucalyptol-type were dominant. Moreover, the borneol-type, cymol-type, elemol-type, methylisoeugenol-type, and selina-6-en-4-ol-type were reported in C. bodinieri for the first time. The yield and principal components of the essential oils were mainly affected by altitude, temperature, and sunshine duration, among which altitude had the most significant effect; thus, low-altitude areas are more suitable for the synthesis and accumulation of essential oils. Based on the different characteristics of the essential oils in the leaves of C. bodinieri, several excellent populations and individuals were identified in this study. Moreover, the findings provide a foundation for breeding superior varieties and studying essential oil biosynthesis mechanisms in the future.

Cinnamomum bodinieri is a tree species highly valued for its superior-quality timber and ecological benefits. However, its large-scale propagation is hindered by the low efficiency of adventitious root (AR) formation. This study investigated the physiological and molecular mechanisms underlying AR formation in C. bodinieri. The results revealed that ARs originate from callus tissue, with the root primordium classified as a latent type. During AR formation, concentrations of soluble protein and soluble sugar decreased, while the activities of superoxide dismutase (SOD), peroxidase (POD), and indole-3-acetic acid oxidase (IAAO) peaked 20 days after cutting (CB2), with polyphenol oxidase (PPO) activity exhibiting an “N”-shaped trend. These findings indicate that substantial nutrient consumption is required for AR formation, with SOD, POD, PPO, and IAAO positively regulating the process. Indole-3-acetic acid (IAA) levels significantly decreased during the early stages of cutting but increased thereafter, whereas the concentration of abscisic acid (ABA) continuously rose. Similar trends were observed for zeatin riboside (ZR) and gibberellic acid (GA). Transcriptome analysis identified 28 key genes involved in plant hormone signal transduction pathways. Furthermore, weighted gene co-expression network analysis (WGCNA) pinpointed 14 hub genes, including CYP94B3 and NAC82, linked to hormone-associated traits. Furthermore, quantitative real-time PCR (qRT-PCR) confirmed the accuracy of the transcriptome sequencing results. This analysis uncovered critical interactions between hormonal signaling pathways and pivotal gene networks. Overall, the findings highlight the central regulatory role of endogenous hormones in AR formation, with IAA serving as the predominant regulator.

Short-chain dehydrogenase/reductases (SDRs) are the largest NAD(H)-dependent oxidoreductase superfamilies and are involved in diverse metabolisms. This study presents a comprehensive genomic analysis of the SDR superfamily in Cinnamomum camphora, a species that is one of the most significant woody essential oil plants in southern China. We identify a total of 222 CcSDR proteins and classify them into five types based on their cofactor-binding and active sites: ‘atypical’, ‘classic’, ‘divergent’, ‘extended’, and ‘unknown’. Phylogenetic analysis reveals three evolutionary branches within the CcSDR proteins, and further categorization using the SDR-initiative Hidden Markov model resulted in 46 families, with the CcSDR110C, CcSDR108E, and CcSDR460A families being the most populous. Collinearity analysis identified 34 pairs of CcSDR paralogs in C. camphora, 141 pairs of SDR orthologs between C. camphora and Populus trichocarpa, and 59 pairs between C. camphora and Oryza sativa. Expression profile analysis indicates a preference for the expression of 77 CcSDR genes in specific organs such as flowers, bark, twigs, roots, leaves, or fruits. Moreover, 77 genes exhibit differential expression patterns during the four developmental stages of leaves, while 130 genes show variance across the five developmental stages of fruits. Additionally, to explore the biosynthetic mechanism of methyl eugenol, a key component of the leaf essential oil in the methyl eugenol chemotype, this study also identifies eugenol synthase (EGS) within the CcSDR460A family through an integrated strategy. Real-time quantitative PCR analysis demonstrates that the expression of CcEGS in the leaves of the methyl eugenol chemotype is more than fourfold higher compared to other chemotypes. When heterologously expressed in Escherichia coli, it catalyzes the conversion of coniferyl acetate into a mixture predominantly composed of eugenol (71.44%) and isoeugenol (21.35%). These insights pave the way for future research into the functional diversity of CcSDR genes, with a focus on secondary metabolism.

1-Deoxy-D-xylulose 5-phosphate synthase (DXS) catalyzes the rate-limiting step of the plastidial 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway and governs carbon flux toward terpenoid biosynthesis. The Lauraceae constitute an economically important plant lineage characterized by specialized terpenoid metabolism and divergent essential-oil chemotypes; however, the evolutionary dynamics and functional divergence of the DXS gene family across this family remain poorly understood. Here, we performed a comprehensive pan-genomic survey of the DXS family across 14 Lauraceae genomes, integrating phylogenomics, synteny analysis, selection-pressure assessment, structural-variation profiling, spatiotemporal expression profiling, and heterologous functional validation. We identified 92 DXS genes assigned to six orthogroups. DXS2 and DXS4 were conserved ohnologs likely derived from the Lauraceae-specific whole-genome duplication, whereas DXS5 and DXS6 underwent recent lineage-specific duplications. All DXS orthogroups were under purifying selection (Ka/Ks < 1), with divergent selection intensities among subclades within Clade 2. Structural variations in DXS genes were predominantly located in introns and untranslated regions rather than coding regions. Spatiotemporal expression profiling in Camphora officinarum revealed distinct tissue-specific expression patterns: CoDXS2 was specifically expressed in developing fruits, CoDXS4 exhibited flower-bud-specific expression, and CoDXS6 was highly expressed in developing leaves and fruits. Notably, CoDXS6 transcript abundance showed a strong positive correlation with monoterpenoid accumulation (r = 0.945, p < 0.001), and functional assays confirmed its canonical catalytic activity. Furthermore, CoDXS6 exhibited 6.32- to 9.18-fold higher leaf expression in terpenoid-dominant chemotypes compared with phenylpropanoid-dominant chemotypes. Collectively, retention following recent whole-genome duplication, recent genome-specific duplications, and regulatory variations jointly drove the functional divergence of Lauraceae DXS genes, highlighting CoDXS6 as a key contributor to leaf monoterpenoid biosynthesis in C. officinarum.