Universal stress proteins (USPs) are typical stress-inducible proteins that function directly in a variety of biotic or abiotic stresses and effectively protect plants from complex, adverse environments. However, the expression patterns of USP genes under pathogen stress and their molecular mechanisms in stress resistance have not been reported in detail. In this study, 46 USP genes were identified from Populus trichocarpa (PtrUSPs), and their biological characteristics were comprehensively analyzed based on phylogeny, physicochemical properties of proteins, and gene structures. The promoter regions of PtrUSPs contain a variety of cis-acting elements related to hormone and stress response. The results of a collinearity analysis showed that PtsrUSPs were highly conserved with homologous genes from four other representative species (Arabidopsis thaliana, Eucalyptus grandis, Glycine max, and Solanum lycopersicum). Furthermore, RNA-Seq analysis showed that the expression of 46 USPs from P. davidiana × P. alba var. pyramidalis Louche (PdpapUSPs) was significantly induced by Fusarium oxysporum. The co-expression network and gene ontology analysis of PtrUSPs showed that they participated in the response to stress and response to stimulus through precise coordination. The results of this paper systematically revealed the biological characteristics of PtrUSPs and the characteristics of their response to F. oxysporum stress, which will lay a theoretical foundation for improving genetic traits and the breeding of poplar disease-resistant varieties in subsequent studies.

An endophytic bacterium Bacillus velezensis BY6 was isolated from the wood stems of healthy Populus davidiana × P. alba var. pyramidalis (PdPap). The BY6 strain can inhibit pathogenic fungus Alternaria alternate in PdPap and promote growth of PdPap seedlings. In the present study, we used the Pacific Biosciences long‐read sequencing platform, a single‐molecule real‐time (SMRT) technology for strain BY6, to perform complete genome sequencing. The genome size was 3,898,273 bp, the number of genes was 4,045, and the average GC content was 47.33%. A complete genome of strain BY6 contained 110 secondary metabolite gene clusters. Nine of the secondary metabolite gene clusters exhibited antifungal activity and promoted growth functions primarily involved in the synthesis of surfactin, bacteriocins, accumulated iron ions, and related antibiotics. Gene clusters provide genetic resources for biotechnology and genetic engineering, and enhance understanding of the relationship between microorganisms and plants.

The growth process of poplar faces severe environmental challenges. Notably, poplar canker, caused by Botryosphaeria dothidea, has significantly impaired poplar productivity and ecological functions. However, research on the molecular mechanisms underlying poplar resistance to this disease remains incomplete. This study systematically elucidated the molecular mechanisms of Populus davidiana × P. alba var. pyramidalis (Pdpap) in response to B. dothidea stress by integrating phenotypic, physiological, biochemical, and transcriptomic analyses. The results demonstrated that 5 d post-inoculation with B. dothidea, the stem wound sites darkened and developed lesions. Following pathogen infection, H₂O₂ content and SOD and POD activity initially increased then decreased, while MDA content overall showed a declining trend with prolonged infection time. KEGG enrichment analysis revealed that DEGs were significantly enriched in the MAPK signaling pathway, plant hormone signal transduction, and phenylpropanoid biosynthesis pathways. Gene modules significantly associated with physiological indices were screened using WGCNA. Within these modules, hub genes in the regulatory network were further identified, leading to the selection of P2C76. The genome-wide identification of PtrPP2Cs classified 124 members into 13 subgroups. Collectively, this study dissects the gene expression regulation and molecular defense mechanisms of poplar under B. dothidea infection, providing novel molecular insights for its molecular breeding.