Pine wood nematode, Bursaphelenchus xylophilus, is a worldwide pest of pine trees, spreading at an alarming rate and with great ecological adaptability. In the process of causing disease, the nematode causes metabolic disorders and changes in the endophytic microbial community of the pine tree. However, the changes at the pine nidus during early nematode invasion have not been well studied, especially the differential metabolites, in Pinus massoniana, the main host of B. xylophilus in China. In this study, we analyzed the endophytic bacterial and fungal communities associated with healthy and B. xylophilus-caused wilted pine trees. The results show that 1333 bacterial OTUs and 502 fungal OTUs were annotated from P. massoniana stem samples. The abundance of bacterial communities in pine trees varies more following infection by B. xylophilus, but the abundance changes of fungal communities are less visible. There were significant differences in endophytic microbial diversity between wilted and healthy P. massoniana. In wilted pine trees, Actinobacteria and Bacteroidia were differential indicators of bacterial communities, whereas, in healthy pine trees, Rhizobiales in the Proteobacteria phylum were the major markers of bacterial communities. Meanwhile, the differential markers of fungal communities in healthy pines are Malasseziales, Tremellales, Sordariales, and Fusarium, whereas Pleosporaceae is the key marker of fungal communities in wilted pines. Our study examines the effect of changes in the endophytic microbial community on the health of pine trees that may be caused by B. xylophilus infection. In parallel, a non-targeted metabolomic study based on liquid mass spectrometry (LC-MS) technology was conducted on pine trees inoculated with pine nematodes and healthy pine trees with a view to identifying key compounds affecting early pine lesions. Ultimately, 307 distinctly different metabolites were identified. Among them, the riboflavin metabolic pathway in pine trees may play a key role in the early pathogenesis of pine wood nematode disease.

Heat shock protein 90 (HSP90) is an evolutionarily conserved molecular chaperone. Numerous studies have shown that it is widely involved in protein folding, assembly, stabilization, activation, and degradation in response to various biotic and abiotic stresses in many normal cellular processes and under stress conditions. We identified 11 members of the CqHSP90 gene family in the quinoa (Chenopodium quinoa) genome by bioinformatics analysis. Phylogenetic tree analysis showed that quinoa was more closely related to dicotyledonous plants than to monocotyledonous plants. Quinoa is susceptible to high-temperature stress during its growth and development. We analyzed the cis-acting elements of its promoter, and found that nearly 1/3 of the cis-acting elements were stress-responsive, and 2/3 of them had heat-responsive elements. The results of qRT-PCR showed that heat shock at 40 °C could induce a high expression of CqHSP90.1c and CqHSP90.6a. Subcellular localization indicates that they are all membrane proteins. At the same time, both CqHSP90.1c and CqHSP90.6a overexpression lines improved the tolerance of Arabidopsis thaliana under high temperature, indicating that both of them had a positive regulatory effect under heat stress. Results of this study could provide useful information for further study on the biological role of CqHSP90.1c and CqHSP90.6a, and provide theoretical basis for quinoa resistance breeding.

Pine wilt disease, caused by Bursaphelenchus xylophilus, poses a serious threat to global pine forest ecosystems and forestry production. Thaumatin-like proteins (TLPs), which belong to the PR-5 family, are known to participate in plant defense, but their roles in pine have not been well characterized. In this study, a comprehensive genome-wide analysis of the TLP gene family was conducted in Pinus taeda. A total of 116 TLP genes were identified and classified into four major clades based on phylogenetic analysis. Gene structure and conserved motif analyses revealed that members within the same clade generally exhibited similar exon–intron organization patterns and conserved motif compositions. Promoter analysis identified numerous cis-regulatory elements associated with stress responses and phytohormone signaling. Transcriptome data from different stages of pine wood nematode infection identified eight TLP genes that exhibited continuous differential expression, and their expression patterns were further confirmed by qRT-PCR. A multilayer regulatory network highlighted MYB and other transcription factors as key upstream regulators, and yeast one-hybrid assays confirmed MYB-mediated regulation. Together, these findings improve our understanding of the TLP gene family in P. taeda and offer valuable candidate genes and regulatory information for future studies on pine resistance to pine wilt disease.

Introduction: The U-box gene family, defined by the presence of a conserved U-box domain, participates in various biological processes, particularly in plant responses to abiotic stress. However, a comprehensive analysis of this gene family in Populus trichocarpa has not yet been conducted. Investigating the characteristics of U-box genes in poplar will deepen our understanding of the molecular mechanisms underlying salt tolerance and provide a theoretical basis for enhancing its environmental adaptability. Methods: In this study, we performed a genome-wide identification and characteristic analysis of the U-box gene family. Analyses included phylogenetic relationships, gene structures, conserved motifs, promoter cis-acting elements, chromosomal distribution, gene duplication events, and synteny with other plant species. In addition, the expression patterns of selected U-box genes under salt stress were validated using quantitative real-time PCR (qRT-PCR). Results: In this study, 103 U-box genes were identified in the P. trichocarpa genome and mapped to 18 chromosomes. These genes encode proteins with molecular weights ranging from 9.5 to 129.3 kDa and isoelectric points between 4.31 and 9.08, with most predicted to localize in the nucleus. Promoter analysis revealed numerous cis-acting elements associated with development, abiotic stress responses, growth regulation, and hormone signaling. Collinearity analysis identified 4 tandem and 30 segmental duplication events. Transcriptome data showed that 40 and 21 PtrPUBs were differentially expressed in roots and leaves, respectively, under salt stress. Discussion: These findings suggest that U-box genes may play important roles in regulating poplar’s salt stress response. Overall, this study provides a theoretical foundation and valuable genetic resources for the identification of salt tolerance genes in poplar.

Quinoa is a high-nutrition crop originating from the Andes Mountains that is tolerant to cold, drought and salt. However, the mechanism of the high-temperature response in quinoa is still unclear. In this study, quinoa line YL-6 was used to analyze the changes in photosynthetic parameters, physiological parameters and the transcriptome after 0, 3, 12 and 24 h of heat stress. Our results showed that photosynthetic parameters, including the maximum quantum yield of PSII (Fv/Fm), steady-state effective quantum yield (ΦPSII_Lss), non-photochemical quenching (NPQ_Lss), and photochemical quenching coefficients (qL_Lss, qP_Lss), decreased significantly under heat stress, whereas the activities of antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), increased significantly at the early stage. The contents of osmotic adjustment substances such as proline, soluble protein and soluble sugar showed a non-single change trend. WGCNA was conducted to group the differentially expressed genes (DEGs) into 12 co-expression modules. Key modules associated with heat perception and signal transduction were identified, and a core regulatory network was subsequently constructed. Hub genes encoding molecular chaperones and transcription factors were screened, among which heat shock proteins (HSPs) were the most prominent. These results could provide a theoretical basis for analyzing the regulatory network of heat stress, exploring heat-resistant genes and introducing and domesticating quinoa.