Effects of Donor Ages and Propagation Methods on Seedling Growth of Platycladus orientalis (L.) Franco in Winter

Chemical Constituents, Antioxidant, and Enzyme Inhibitory Potentials Supported by In-Silico Studies of the n-Hexane Extract and Essential Oil of Platycladus Orientalis (L.) Franco Leaves

Platycladus orientalis leaves are widely used in traditional medicine to treat different ailments. In the present study, the volatile constituents were obtained by n-hexane extraction and hydrodistillation. Comprehensive metabolomic profiling was performed using GC-MS analysis. Furthermore, in vitro antioxidant potential and enzyme-inhibitory activity were assessed and supported by in silico profiling. Results revealed the predominance of monoterpene hydrocarbons in the hydrodistilled volatile oil (42.30 %) followed by oxygenated sesquiterpenes (32.10 %); with cedrol as the main component. Diterpenoids (49.70 %) and sesquiterpene hydrocarbons (13.43 %) were the major components of the n-hexane extract; with vulgarol A, a diterpene alcohol, as the major constituent. The volatile oil demonstrated significantly higher antioxidant potential across all assays, including ABTS and DDPH scavenging activity, CUPRAC, and FRAP assays. However, the n-hexane extract demonstrated broad inhibitory effects against butyrylcholinesterase, tyrosinase, α-amylase, and α-glucosidase enzymes, supported by molecular docking study and predictive ADME profiling. Therefore, it may be concluded that the n-hexane extract is a viable option for treating dysregulated enzyme conditions. In addition, the potential use of volatile oil in the pharmaceutical industries and management of oxidative stress can be inferred. These results warrant further studies to validate the therapeutic potential of the volatile oil and the n-hexane extract.

Physiological response and molecular mechanism of Quercus variabilis under cadmium stress

Heavy metal pollution is a global environmental problem, and Quercus variabilis has a stronger tolerance to Cd stress than do other species. We aimed to explore the physiological response and molecular mechanisms of Q. variabilis to Cd stress. In this study, the antioxidant enzyme activities of leaves were determined, while the photosynthetic parameters of leaves were measured using Handy PEA, and ion fluxes and DEGs in the roots were investigated using noninvasive microtest technology (NMT) and RNA sequencing techniques, respectively. Cd stress at different concentrations and for different durations affected the uptake patterns of Cd2+ and H+ by Q. variabilis and affected the photosynthetic efficiency of leaves. Moreover, there was a positive relationship between antioxidant enzyme (CAT and POD) activity and Cd concentration. Transcriptome analysis revealed that many genes, including genes related to the cell wall, glutathione metabolism, ion uptake and transport, were significantly upregulated in response to cadmium stress in Q. variabilis roots. WGCNA showed that these DEGs could be divided into eight modules. The turquoise and blue modules exhibited the strongest correlations, and the most significantly enriched pathways were the phytohormone signaling pathway and the phenylpropanoid biosynthesis pathway, respectively. These findings suggest that Q. variabilis can bolster plant tolerance by modulating signal transduction and increasing the synthesis of compounds, such as lignin, under Cd stress. In summary, Q. variabilis can adapt to Cd stress by increasing the activity of antioxidant enzymes, and regulating the fluxes of Cd2+ and H+ ions and the expression of Cd stress-related genes.

Full-length transcriptome characterization of Platycladus orientalis based on the PacBio platform

As a unique and native conifer in China, Platycladus orientalis is widely used in soil erosion control, garden landscapes, timber, and traditional Chinese medicine. However, due to the lack of reference genome and transcriptome, it is limited to the further molecular mechanism research and gene function mining. To develop a full-length reference transcriptome, tissues from five different parts of P. orientalis and four cone developmental stages were sequenced and analyzed by single-molecule real-time (SMRT) sequencing through the PacBio platform in this study. Overall, 37,111 isoforms were detected by PacBio with an N50 length of 2,317 nt, an average length of 1,999 bp, and the GC content of 41.81%. Meanwhile, 36,120 coding sequences, 5,645 simple sequence repeats (SSRs), 1,201 non-coding RNAs (lncRNAs), and 182 alternative splicing (AS) events with five types were identified using the results obtained from the PacBio transcript isoforms. Furthermore, 1,659 transcription factors (TFs) were detected and belonged to 51 TF families. A total of 35,689 transcripts (96.17%) were annotated through the NCBI nr, KOG, Swiss-Prot and KEGG databases, and 385 transcript isoforms related to 8 types of hormones were identified incorporated into plant hormone signal transduction pathways. The assembly and revelation of the full-length transcriptome of P. orientalis offer a pioneering insight for future investigations into gene function and genetic breeding within Platycladus species.

Effects of Different Donor Ages on the Growth of Cutting Seedlings Propagated from Ancient Platycladus orientalis

The effects of tree age on the growth of cutting seedlings propagated from ancient trees have been an important issue in plant breeding and cultivation. In order to understand seedling growth and stress resistance stability, phenotypic measurements, physiological assays, and high-throughput transcriptome sequencing were performed on sown seedlings propagated from 5-year-old donors and cutting seedlings propagated from 5-, 300-, and 700-year-old Platycladus orientalis donors. In this study, the growth of cutting seedlings propagated from ancient trees was significantly slower; the soluble sugar and chlorophyll contents gradually decreased with the increase in the age of donors, and the flavonoid and total phenolic contents of sown seedlings were higher than those of cutting seedlings. Enrichment analysis of differential genes showed that plant hormone signal transduction, the plant-pathogen interaction, and the flavone and flavonol biosynthesis pathways were significantly up-regulated with the increasing age of cutting seedlings propagated from 300- and 700-year-old donors. A total of 104,764 differentially expressed genes were calculated using weighted gene co-expression network analysis, and 8 gene modules were obtained. Further, 10 hub genes in the blue module were identified, which revealed that the expression levels of JAZ, FLS, RPM1/RPS3, CML, and RPS2 increased with the increase in tree age. The results demonstrated that the age of the donors seriously affected the growth of P. orientalis cutting seedlings and that cutting propagation can preserve the resistance of ancient trees. The results of this study provide important insights into the effects of age on asexually propagated seedlings, reveal potential molecular mechanisms, and contribute to an improvement in the level of breeding and conservation of ancient germplasm resources of P. orientalis trees.