Background: As important forest tree species, biological stress and soil salinization are important factors that restrict the growth of Populus × euramericana. WRKYs are important transcription factors in plants that can regulate plant responses to biotic and abiotic stresses. In this study, PeWRKY31 was isolated from Populus × euramericana, and its bioinformation, salt resistance and insect resistance were analyzed. This study aims to provide guidance for producing salt-resistant and insect-resistant poplars. Results: PeWRKY31 has a predicted open reading frame (ORF) of 1842 bp that encodes 613 amino acids. The predicted protein is the unstable, acidic, and hydrophilic protein with a molecular weight of 66.34 kDa, and it has numerous potential phosphorylation sites, chiefly on serines and threonines. PeWRKY31 is a zinc-finger C₂H₂ type-II WRKY TF that is closely related to WRKY TFs of Populus tomentosa, and localizes to the nucleus. A PeWRKY31 overexpression vector was constructed and transformed into Nicotiana tabacum L. Overexpression of PeWRKY31 improved the salt tolerance and insect resistance of the transgenic tobacco. Transcriptome sequencing and KEGG enrichment analysis showed the elevated expression of genes related to glutathione metabolism, plant hormone signal transduction, and MAPK signaling pathways, the functions of which were important in plant salt tolerance and insect resistance in the overexpressing tobacco line. Conclusions: PeWRKY31 was isolated from Populus × euramericana. Overexpression of PeWRKY31 improved the resistance of transgenic plant to salt stress and pest stress. The study provides references for the generation of stress-resistant lines with potentially great economic benefit.

Elm (Ulmus) species are important components of forest resources with significant ecological and economic value. As tall hardwood trees that are drought-resistant, poor-soil-tolerant, and highly adaptable, Ulmus species are an excellent choice for ecologically protected forests and urban landscaping. Additionally, the bioactive substances identified in the fruits, leaves, bark, and roots of Ulmus have potential applications in the food and medical fields and as raw materials in industrial and cosmetic applications. However, the survival of Ulmus species in the natural environment has been threatened by recurrent outbreaks of Dutch elm disease, which have led to the death of large numbers of Ulmus trees. In addition, severe damage to the natural habitats of some Ulmus species is driving their populations to extinction. Omics technology has become an important tool for the collection, protection, and biological characteristic analysis of Ulmus species and their resources due to its recent advances. This article summarizes the current research and application status of omics technology in Ulmus. The remaining problems are noted, and future research directions are proposed. Our review is aimed at providing a reference for resource conservation of Ulmus and for scientific research into this genus.

Ulmus pumila L. ‘Zhonghua Jinye’ is a plant variety with colourful leaves that is widely used in landscaping. In our study, the leaves of U. pumila ‘Zhonghua Jinye’ fade and turn green under light (LT, 45%), moderate (MD, 70%) and high (HG, 95%) shading treatment, reducing its ornamental value. However, the mechanism underlying this adaptation to shade is poorly understood. The objective of this study was to elucidate the mechanism of physiological, cellular microstructural and transcriptional changes involved in leaf regreening in U. pumila ‘Zhonghua Jinye’. Our results showed that the pigment content of U. pumila ‘Zhonghua Jinye’ leaves increased under shade stress, with a corresponding colour change from yellow to dark green. Thus, U. pumila ‘Zhonghua Jinye’ adapted to shade stress by increasing leaf pigment and chlorophyll content. Transmission electron microscopy showed that thylakoid stacking in the grana lamellae changed significantly from a loose state to a closely packed structure under shaded conditions. Because plant pigments were located mainly in thylakoids, this closer stacking increased photosynthetic efficiency and pigment accumulation. RNA sequencing analysis showed that Lhcb1, a key thylakoid membrane gene, was upregulated under shade, which promoted thylakoid stacking and light absorption. In the chlorophyll synthesis pathway, haeme metabolism was inhibited, increasing protoporphyrin IX flow to the chlorophyll pathway and promoting the synthesis of chlorophyll a/b. The simultaneous upregulation of plant hormone-related genes promoted an increase in plant leaf area, improving the light energy utilisation ratio. This study is the first to report the self-regulatory mechanism that leads to colour change in U. pumila ‘Zhonghua Jinye’ under shade stress and provides a theoretical basis for the cultivation of tree species with colourful leaves.

Manchurian walnut (Juglans mandshurica) is a rare woody oil tree and a key species for ecological restoration in northern China. The Wulingshan National Nature Reserve serves as the core germplasm habitat within its distribution range. However, the coupling mechanism between fruit traits of wild germplasm and soil environment in this region has not been systematically evaluated, restricting germplasm conservation and breeding utilization. In this study, 50 wild J. mandshurica germplasm accessions from the reserve were analyzed. Fruit phenotypic traits, kernel quality traits and rhizosphere soil nutrient indices were determined, and comprehensive germplasm evaluation was conducted via variation analysis, cluster analysis, principal component analysis, membership function method and correlation analysis. The coefficients of variation of 20 quantitative traits ranged from 6.58% to 45.17%, with quality traits showing higher variability than phenotypic traits. The average kernel oil content reached 59.46%. The 50 accessions were clustered into four distinct groups with significantly divergent trait profiles. With increasing elevation, soil properties such as soil hydrolyzable nitrogen, available phosphorus, and electrical conductivity all showed a consistent decreasing trend. For J. mandshurica, green fruit length, green fruit width, the three principal nut diameters, and nut starch content, together with the aforementioned soil hydrolyzable nitrogen and electrical conductivity, were all negatively correlated with elevation. Six germplasm accessions (A32, A42, A34, A21, A47, A15) with excellent comprehensive traits were finally selected. This study clarifies the germplasm variation characteristics of J. mandshurica in Wulingshan and the regulatory effects of soil environmental factors, providing a scientific basis for its resource conservation and targeted breeding.

To enrich the breeding resources of Xanthoceras sorbifolium and provide support for its industrialization, we conducted multi-trait comparisons and comprehensive evaluations of 48 elite X. sorbifolium clones with high oil contents and high comprehensive utilization values, based on germplasms preserved at Qiuxian Forest Farm, Handan, Hebei Province, China. The coefficients of variation for quantitative traits were 7.04–74.16%, with variability being greatest in shell and fruit weights. Cluster analysis categorized the 48 germplasms into four distinct groups, with marked inter-group trait differences. Soluble protein, soluble sugar, and starch contents varied significantly among accessions. The average kernel oil content was 60.30%, differences in oil content were validated at the cellular level through microscopic oil body observations. Correlation analysis demonstrated that comprehensive oil content was strongly significantly positively correlated with fruit- and seed-related traits, whereas oil content was strongly significantly negatively correlated with fruit shell thickness and seed coat thickness. Principal component analysis extracted five principal components with a cumulative contribution rate of 72.747%, encapsulating four core information dimensions: fruit and seed size, oil content, protein quality, and energy substances. Membership function analysis, selected germplasms G10, G2, G4, G7, G20, G24, G17, G1, G34, and G5 as optimal accessions. These clones are suitable core breeding materials due to their outstanding performance in terms of nutrient content, geometric characteristics, and fruit and seed weights. Notably, G24, G5, and G17 demonstrated significant advantages in oil quality with high linoleic acid (C18:2), oleic acid (C18:1), and nervonic acid (C24:1) contents, respectively, indicating the excellent potential of X. sorbifolium development for oil production.