Cinnamomum camphora has been cultivated as an economically important tree for its medicinal and aromatic properties. Selective breeding has produced Cinnamomum plants for special uses, including spice strains with characteristic flavors and aromas and high-potency medicinal cultivars. The molecular biology underlying terpenoid biosynthesis is still unexplored. Gas chromatography-mass spectrometry was used to analyze the differences in contents and compositions of essential oil terpenoids in linalool- and borneol-type chemotypes of C. camphora. The data revealed that the essential oils consist primarily of monoterpenes with only very minor quantities of sesquiterpenes and diterpenes and that the essential oil differs in different chemotypes of C. camphora, with higher yields of (−)-borneol from the borneol-type than from the linalool-type. To study the terpenoid biosynthesis of signature compounds of the major monoterpenes, we performed RNA sequencing to profile the leaf transcriptomes of the two chemotypes of C. camphora. A total of 23.76 Gb clean data was generated from two chemotypes and assembled into 156,184 unigenes. The total length, average length, N50 and GC content of unigenes were 155,645,929 bp, 997 bp, 1430 bp, and 46.5%, respectively. Among them, 76,421 unigenes were annotated by publicly available databases, of which 67 candidate unigenes were identified to be involved in terpenoid biosynthesis in C. camphora. A total of 2863 unigenes were identified to be differentially expression between borneol-type and linalool-type, including 1714 up-regulated and 1149 down-regulated unigenes. Most genes encoding proteins involved in terpenoid precursor MVA and MEP pathways were expressed in similar levels in both chemotypes of C. camphora. In addition, 10 and 17 DEGs were significantly enriched in the terpene synthase activity and oxidoreductase activity terms of their directed acyclic graphs (DAG), respectively. Three monoterpene synthase genes, TPS14-like1, TPS14-like2 and TPS14-like3 were up-regulated in the borneol-type compared to the linalool-type, and their expression levels were further verified using quantitative real-time PCR. This study provides a global overview of gene expression patterns related to terpenoid biosynthesis in C. camphora, and could contribute to a better understanding of the differential accumulation of terpenoids in different C. camphora chemotypes.

Drought stress (DS) is a potential abiotic stress that is substantially reducing crop productivity across the globe. Likewise, salinity stress (SS) is another serious abiotic stress that is also a major threat to global crop productivity. The rapid climate change increased the intensity of both stresses which pose a serious threat to global food security; therefore, it is urgently needed to tackle both stresses to ensure better crop production. Globally, different measures are being used to improve crop productivity under stress conditions. Among these measures, biochar (BC) has been widely used to improve soil health and promote crop yield under stress conditions. The application of BC improves soil organic matter, soil structure, soil aggregate stability, water and nutrient holding capacity, and the activity of both beneficial microbes and fungi, which leads to an appreciable increase in tolerance to both damaging and abiotic stresses. BC biochar protects membrane stability, improves water uptake, maintains nutrient homeostasis, and reduces reactive oxygen species production (ROS) through enhanced antioxidant activities, thereby substantially improving tolerance to both stresses. Moreover, BC-mediated improvements in soil properties also substantially improve photosynthetic activity, chlorophyll synthesis, gene expression, the activity of stress-responsive proteins, and maintain the osmolytes and hormonal balance, which in turn improve tolerance against osmotic and ionic stresses. In conclusion, BC could be a promising amendment to bring tolerance against both drought and salinity stresses. Therefore, in the present review, we have discussed various mechanisms through which BC improves drought and salt tolerance. This review will help readers to learn more about the role of biochar in causing drought and salinity stress in plants, and it will also provide new suggestions on how this current knowledge about biochar can be used to develop drought and salinity tolerance.

Cinnamomum species attract attentions owing to their scents, medicinal properties, and ambiguous relationship in the phylogenetic tree. Here, we report a high-quality genome assembly of Cinnamomum camphora, based on which two whole-genome duplication (WGD) events were detected in the C. camphora genome: one was shared with Magnoliales, and the other was unique to Lauraceae. Phylogenetic analyses illustrated that Lauraceae species formed a compact sister clade to the eudicots. We then performed whole-genome resequencing on 24 Cinnamomum species native to China, and the results showed that the topology of Cinnamomum species was not entirely consistent with morphological classification. The rise and molecular basis of chemodiversity in Cinnamomum were also fascinating issues. In this study, six chemotypes were classified and six main terpenoids were identified as major contributors of chemodiversity in C. camphora by the principal component analysis. Through in vitro assays and subcellular localization analyses, we identified two key terpene synthase (TPS) genes (CcTPS16 and CcTPS54), the products of which were characterized to catalyze the biosynthesis of two uppermost volatiles (i.e. 1,8-cineole and (iso)nerolidol), respectively, and meditate the generation of two chemotypes by transcriptional regulation and compartmentalization. Additionally, the pathway of medium-chain triglyceride (MCT) biosynthesis in Lauraceae was investigated for the first time. Synteny analysis suggested that the divergent synthesis of MCT and long-chain triglyceride (LCT) in Lauraceae kernels was probably controlled by specific medium-chain fatty acyl-ACP thioesterase (FatB), type-B lysophosphatidic acid acyltransferase (type-B LPAAT), and diacylglycerol acyltransferase 2b (DGAT 2b) isoforms during co-evolution with retentions or deletions in the genome.

Machilus robusta W. W. Smith is an evergreen plant distributed in the Yangtze River Basin and the south regions of China. Here we analyzed the complete chloroplast (cp) genome sequence of M. robusta to determine its structure and evolutionary relationship to other Lauraceae. The cp genome is 152,737 bp in length and has an overall GC content of 39.2% The genome includes a large single-copy (LSC) region of 93,706 bp and a small single-copy (SSC) region of 18,885 bp, and these are separated by a pair of inverted repeats (IRs) of 20,073 bp. The cp genome contains 128 genes, including 83 protein-coding, 37 tRNAs, and 8 rRNAs. Phylogenetic analysis based on complete cp genome sequences fully resolved M. robusta in a clade with M. balansae. This work provides new molecular data for evolutionary studies of the Lauraceae.

Phoebe bournei is an important economic tree species in China, its large-scale propagation is limited by the difficulty of adventitious root (AR) formation in cuttings. In this study, morphological, physiological, and transcriptomic analyses were conducted to investigate the process of AR formation in P. bournei. The results showed that ARs mainly originated from callus tissue. During AR formation, soluble sugar and soluble protein contents changed significantly. Malondialdehyde (MDA) and oxygen free radicals (OFRs) peaked at first sampling stage (PB0), while the activities of polyphenol oxidase (PPO) and indoleacetic acid oxidase (IAAO) exhibited similar patterns. Lignin content increased during callus induction stage, whereas phenolic content continuously declined throughout rooting. Endogenous hormone levels also changed markedly, and Orthogonal partial least squares discriminant analysis (OPLS-DA) analysis indicated that indole-3-acetic acid (IAA) and abscisic acid (ABA) played dominant roles in this process. KEGG enrichment analysis revealed significant enrichment of the phenylpropanoid biosynthesis pathway in all three comparison groups. A total of 48 differentially expressed genes (DEGs) were enriched in plant hormone signal transduction pathways, with 22 and 14 genes associated with IAA and ABA signaling, respectively. Weighted gene co-expression network analysis (WGCNA) further identified two hub modules related to IAA and ABA contents, including eight hub genes such as D6PKL1 and ISTL1. Correlation analysis revealed that the hub genes D6PKL1 and HSP were significantly positively correlated with IAA4 in the IAA signaling pathway. Overall, this study provides new insights into the mechanisms underlying AR formation in P. bournei cuttings and offers a theoretical basis for optimizing its clonal propagation system.

A pluripotent callus is central to genetic transformation in Cinnamomum parthenoxylon; however, the molecular and cellular mechanisms regulating callus formation and subsequent differentiation remain unelucidated, hindering progress in its genetic improvement. This study systematically investigated the dynamic changes during the in vitro regeneration of C. parthenoxylon through morphological observations, physiological assays, and transcriptomic analyses, while comparing differences in callus formation under varying induction conditions to elucidate the mechanism of its high-efficiency regeneration. The results showed that the formation of a pluripotent callus is a critical step in C. parthenoxylon regeneration, characterized by the presence of highly proliferative cell zones. Compared to an ordinary callus (P3C), a pluripotent callus (P3) exhibited higher activities of polyphenol oxidase (PPO) and indole-3-acetic acid oxidase (IAAO), as well as elevated levels of zeatin riboside (ZR) and abscisic acid (ABA). In contrast, P3 showed lower levels of soluble sugars, soluble proteins, malondialdehyde (MDA), indole-3-acetic acid (IAA), and gibberellins (GA), a reduced IAA/ZR ratio, and diminished peroxidase (POD) activity. Weighted gene co-expression network analysis (WGCNA) identified 27 hub transcription factors (TFs) strongly associated with IAA/ZR, primarily from the ERF, bHLH, MYB, WRKY, and C3H families. Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses revealed the significant enrichment of differentially expressed genes (DEGs) related to plant hormone signal transduction and cell wall metabolism during pluripotent callus acquisition. Further investigations revealed that five genes encoding a putative indole-3-acetic acid-amido synthetase GH3.1, protein TIFY 10A, a two-component response regulator ARR2-like isoform X2, and xyloglucan endotransglucosylase/hydrolase, likely promoting callus pluripotency by modulating plant hormone signaling and cell wall metabolism, thereby enhancing in vitro regeneration in C. parthenoxylon. In summary, this study provides critical insights into the molecular mechanisms of C. parthenoxylon regeneration and offers valuable germplasm resources for establishing an efficient and stable genetic transformation system via tissue culture.