Populus cathayana Rehder, an indigenous poplar species of ecological and economic importance, is widely distributed in a high-elevation range from southwest to northeast China. Further development of this species as a sustainable poplar resource has been hindered by a lack of genome information the at the population level. Here, we produced a chromosome-level genome assembly of P. cathayana, covering 406.55 Mb (scaffold N50 = 20.86 Mb) and consisting of 19 chromosomes, with 35 977 protein-coding genes. Subsequently, we made a genomic variation atlas of 438 wild individuals covering 36 representative geographic areas of P. cathayana, which were divided into four geographic groups. It was inferred that the Northwest China regions served as the genetic diversity centers and a population bottleneck happened during the history of P. cathayana. By genotype–environment association analysis, 947 environment-association loci were significantly associated with temperature, solar radiation, precipitation, and altitude variables. We identified local adaptation genes involved in DNA repair and UV radiation response, among which UVR8, HY5, and CUL4 had key roles in high-altitude adaptation of P. cathayana. Predictions of adaptive potential under future climate conditions showed that P. cathayana populations in areas with drastic climate change were anticipated to have greater maladaptation risk. These results provide comprehensive insights for understanding wild poplar evolution and optimizing adaptive potential in molecular breeding.

Objectives: The objective of our project is to explore a noninvasive radiomics model based on magnetic resonance imaging (MRI) that could recognize the expression of vascular endothelial growth factor (VEGF) in hepatocellular carcinoma before operation.Methods: 202 patients with proven single HCC were enlisted and stochastically distributed into a training set (n = 142) and a test set (n = 60). Arterial phase, portal venous phase, balanced phase, delayed phase, and hepatobiliary phase images were used to radiomics features extraction. We retrieved 1906 radiomic features from each phase of every participant’s MRI images. The F-test was applied to choose the crucial features. A logistic regression model was adopted to generate a radiomics signature. By combining independent risk indicators from the fusion radiomics signature and clinico-radiological features, we developed a multivariable logistic regression model that could predict the VEGF status preoperatively through calculating the area under the curve (AUC).Results: The entire group comprised 108 VEGF-positive individuals and 94 VEGF-negative patients. AUCs of 0.892 (95% confidence interval [CI]: 0.839 - 0.945) in the training dataset and 0.800 (95% CI: 0.682 - 0.918) in the test dataset were achieved by utilizing radiomics features from two phase images (8 features from the portal venous phase and 5 features from the hepatobiliary phase). Furthermore, the nomogram relying on a combined model that included the clinical factors α-fetoprotein (AFP), irregular tumor margin, and the fusion radiomics signature performed well in both the training (AUC = 0.936, 95% CI: 0.898-0.974) and test (AUC = 0.836, 95% CI: 0.728-0.944) datasets.Conclusions: The combined model acquired from two phase (portal venous and hepatobiliary phase) pictures of gadolinium-ethoxybenzyl-diethylenetriamine-pentaacetic acid (Gd-EOB-DTPA)-enhanced MRI could be considered as a credible prognostic marker for the level of VEGF in HCC.

Leaf morphology plays a crucial role in predicting the productivity and environmental adaptability of forest trees, making it essential to understand the genetic mechanisms behind leaf variation. In natural populations of Populus cathayana, leaf morphology exhibits rich intraspecific variation due to long-term selection. However, there have been no studies that systematically reveal the genetic mechanisms of leaf variation in P. cathayana. To fill this gap and enhance our understanding of leaf variation in P. cathayana, we collected nine leaf traits from the P. cathayana natural population, consisting of 416 accessions, and conducted the preliminary classification of leaf types with four categories. Subsequently, we conducted an analysis of selective sweep and genome-wide association studies (GWAS) to uncover the genetic basis of leaf traits variation. Most of the leaf traits displayed significant correlations, with broad-sense trait heritability ranging from 0.38 to 0.74. In total, three selective sweep methods ultimately identified 278 positively selected candidate regions and 493 genes associated with leaf size. Single-trait and multi-trait GWAS methods detected 13 and 59 genes, respectively. By integrating the results of selective sweep and GWAS, we further identified a total of nine overlapping genes. These genes may play a role in the leaf development process and are closely associated with leaf size. In particular, the gene CBSCBSPB3 (Pca07G009100) located on chromosome 7, was associated with the response to light stimulation. This study will deepen our understanding of the genetic mechanism of leaf adaptive variation in P. cathayana and provide valuable gene resources.

The adventitious root (AR) is the basis for successful propagation by plant cuttings and tissue culture and is essential for maintaining the positive traits of a variety. Members of the amino acid/auxin permease (AAAP) gene family play indispensable roles in various plant metabolisms and have few studies on root growth and amino acid transport. In this study, with a systematic bioinformatics analysis of the Populus AAAP family, 83 PtrAAAPs were identified from Populus trichocarpa and grouped into 8 subfamilies. Subsequently, chromosomal distribution, genetic structure, cis-elements analysis, and expression pattern analysis of the AAAP family were performed and the potential gene AAAP21 regulating root development was screened by combining the results of RNA-Seq and QTL mapping. PsAAAP21 was proven as promoting root development by enhancing AR formation. Differentially expressed genes (DEGs) from RNA-seq results of overexpressing lines were enriched to multiple amino acid-related pathways, and the amino acid treatment to transgenic lines indicated that PsAAAP21 regulated amino acid transport, including tyrosine, methionine, and arginine. Analysis of the AAAP gene family provided a theoretical basis for uncovering the functions of AAAP genes. The identification of PsAAAP21 on root promotion and amino acid transport in Populus will help with breeding new woody plant species with strong rooting ability.

Poplar provides a large amount of bioenergy and wood, but the lack of soil nitrogen in poplar plantations has seriously restricted its wood production. Using Populus deltoides ‘Danhong’, P. simonii ‘Tongliao1’, and their F₁ populations as materials, nitrogen fertilizer and no nitrogen fertilizer were applied in the field. Under different nitrogen conditions, the wood yield of ‘Danhong’ was much higher than that of ‘Tongliao 1’, which indicated that ‘Danhong’ had excellent genetic resources related to nitrogen use efficiency (NUE). Based on a high‐density genetic map, we performed quantitative trait loci (QTL) analyses for ground diameter, plant height, stem biomass, and nitrogen response index. A total of 276 QTLs and 774 candidate genes were identified. We analysed the metabolites related to carbon and nitrogen metabolism and the transcriptome of the developing xylem in 10 clones under high‐ and low‐nitrogen conditions. Through weighted gene coexpression network analysis, it was found that the MEyellow module was closely related to biomass, carbon, and nitrogen metabolism, and a gene coexpression network was established. Finally, candidate genes NRT3.1, NPF5.1, NPF5.10, and NPF8.1 related to nitrogen transport; transcription factors NLP8.1, NLP8.2, and NLP2 regulating nitrogen transport; genes Potri.010G070900, GDH2, and SHM2 related to amino acid metabolism; and genes Necap2, Dscr3, trappc2l, Potri.013G072600, and LAX2 related to carbon metabolism were identified. This work provides abundant genetic resources for the genetic improvement of poplar NUE and provides new insights into the linkage mechanism between NUE and biomass yield.

As a crucial ecological shelterbelt and timber species in China, Populus relies on adventitious root (AR) formation and root architecture for its ecological adaptability and clonal propagation efficiency. Two key root trait-related genes, PcabHLH58 and PcabHLH151, were identified through genome-wide association studies (GWAS) in Populus cathayana. Single or double mutations of PcabHLH58 and PcabHLH151 significantly inhibited AR development and nitrogen uptake in poplar. Furthermore, both genes can form homodimers or heterodimers to modulate the expression of PcaSCL33 and PcaPLT1 during AR development. The higher expression level and stronger regulatory capacity of PcabHLH58 imply its more critical role in the AR development. Additionally, PcaWOX5 was found to be modulated through both the PcabHLH58/PcabHLH151-PcaSCL33/PcaSHR and PcabHLH58/PcabHLH151-PcaPLT1 pathway. PcaPAR1 was identified as a feedback regulatory node in modulating the regulatory activities of both PcabHLH58 and PcabHLH151. Collectively, this study elucidates a novel regulatory network involving root development in poplar and provides foundational insights for future genetic breeding efforts.