Populus species, particularly P. trichocarpa, have long served as model trees for genomics research, owing to fully sequenced genomes. However, the high heterozygosity, and the presence of repetitive regions, including centromeres and ribosomal RNA gene clusters, have left 59 unresolved gaps, accounting for approximately 3.32% of the P. trichocarpa genome. In this study, the callus induction method was improved to derive a doubled haploid (DH) callus line from P. ussuriensis anthers. Leveraging long-read sequencing, we successfully assembled a nearly gap-free, telomere-to-telomere (T2T) P. ussuriensis genome spanning 412.13 Mb. This genome assembly contains only seven gaps and has a contig N50 length of 19.50 Mb. Annotation revealed 34,953 protein-coding genes in this genome, which is 465 more than that of P. trichocarpa. Notably, centromeric regions are characterized by higher-order repeats, we identified and annotated centromere regions in all DH genome chromosomes, a first for poplars. The derived DH genome exhibits high collinearity with P. trichocarpa and significantly fills gaps present in the latter's genome. This T2T P. ussuriensis reference genome will not only enhance our understanding of genome structure, and functions within the poplar genus but also provides valuable resources for poplar genomic and evolutionary studies.

Aralia elata is a perennial woody plant of the genus Aralia in the family Araliaceae. It is rich in saponins and therefore has a wide range of pharmacological effects. Here, we report a high-quality reference genome of A. elata, with a genome size of 1.21 Gb and a contig N50 of 51.34 Mb, produced by PacBio HiFi sequencing technology. This is the first genome assembly for the genus Aralia. Through genome evolutionary analysis, we explored the phylogeny and whole genome duplication (WGD) events in the A. elata genome. The results indicated that a recent WGD event occurred in the A. elata genome. Estimation of the divergence times indicated that the WGD may be shared by Araliaceae. By analyzing the genome sequence of A. elata and combining the transcriptome data from three tissues, we discovered important genes related to triterpene saponins biosynthesis. Furthermore, based on the embryonic callus induction system of A. elata established in our laboratory, we set up the genetic transformation system of this plant. The genomic resources and genetic transformation system obtained in this study provide insights into A. elata and lays the foundation for further exploration of the A. elata regulatory mechanism.

Eleutherococcus senticosus is a medicinal plant with prominent potential for pharmaceutical preparation that is naturally distributed in Northeast China. Its dried roots, stems, and fruits can be used as herbal medicine with anti-aging, anti-fatigue, anti-inflammatory, and other health benefits. With the continuous increasing of E. senticosus planting areas, some problems, such as a reduction in growth rate, fruit yield, and medicinal substances content, have become serious restricting factors for the long-term stable development of the E. senticosus industry. Therefore, the screening and selection of superior provenances, families or clones with high growth rates and high contents of medicinal substances, is urgent. In this study, 13 provenances of E. senticosus were analyzed and evaluated for growth, leaf, photosynthetic, and medicinal traits. The results showed that the majority of traits exhibited highly significant differences (p < 0.01) among provenances. The phenotypic coefficient of the variation of each trait ranged from 4.8% for leaf water content to 70.9% for total flavonoid content. The narrow-sense heritability of each trait ranged from 0.20 ± 0.23 for WUE to 0.39 ± 0.14 for DB. The variance component of all traits reached a high level, with a range of 62.9% (DB) to 99.6% (SC). The correlation analysis showed significant positive correlations between tree height, total flavonoid content, and syringin content. A multi-trait comprehensive evaluation approach enabled the selection of two provenances with 10% acceptance rate (XQ and QY). The subsequent genetic gains for tree height, total flavonoid content, and syringin content were 1.7%, 9.2%, and 20.1%, respectively. In conclusion, the present study provides a fundamental basis for the cultivation and promotion of the superior materials of E. senticosus.

Aralia elata is an important herb due to the abundance of pentacyclic triterpenoid saponins whose important precursors are squalene and OA. Here, we found that MeJA treatment promoted both precursors accumulation, especially the latter, in transgenic A. elata, overexpressing a squalene synthase gene from Panax notoginseng(PnSS). In this study, Rhizobium-mediated transformation was used to express the PnSS gene. Gene expression analysis and high-performance liquid chromatography (HPLC) were used to identify the effect of MeJA on squalene and OA accumulation. The PnSS gene was isolated and expressed in A. elata. Transgenic lines showed a very high expression of the PnSS gene and farnesyl diphosphate synthase gene (AeFPS) and a slightly higher squalene content than the wild-type, but endogenous squalene synthase (AeSS), squalene epoxidase (AeSE), and β-amyrin synthase (Aeβ-AS) gene were decreased as well as OA content. Following one day of MeJA treatment, the expression levels of PeSS, AeSS, and AeSE genes increased significantly. On day 3, the maximum content of both products reached 17.34 and 0.70 mg·g^−1, which increased 1.39- and 4.90-fold than in the same lines without treatment. Transgenic lines expressing PnSS gene had a limited capability to promote squalene and OA accumulation. MeJA strongly activated their biosynthesis pathways, leading to enhance yield.