Post-sunset supplemental light promotes Picea seedling stem elongation, but the underlying hormonal regulation mechanisms on interspecific differences in spruce growth response to photoperiod remain unclear. This study aimed to clarify the physiological mechanism underlying the response of two Picea species to different supplemental light durations. Three-year-old seedlings of P. abies and P. crassifolia were subjected to 0 (CK), 4, 8, and 12 h of post-sunset supplemental light treatments for two growing seasons, with growth characteristics and endogenous hormone contents analyzed. The results showed that species and the interaction between species and photoperiod were the principal factors driving phenotypic divergence in spruce growth traits. Supplemental light treatments significantly promoted sustained growth of P. abies, with 4 h treatment being optimal. This treatment also resulted in the highest levels of gibberellins (GAs) and zeatin riboside (ZR), as well as the highest ratios of ZR/GAs. For P. crassifolia, supplemental light treatment promoted dry matter accumulation (8 h treatment being optimal) but had no significant effect on other growth traits, most endogenous hormones (ZR, IAA), and their ratios across treatments. Correlation and causal inference mediation analysis suggest that ZR and the ZR/IAA ratio could be the main factors driving shoot elongation. Thus, the findings provide a valuable insight for optimizing species-specific supplemental light regimes for seedling production in nurseries.

Hybrid breeding enhances forest genetic improvement by conferring offspring stronger vitality through gene recombination. This study used Catalpa bungei(Q), Catalpa fargesii f. duclouxi(D), and Catalpa fargesii(H) for artificial hybridization, with a natural C. fargesii f. duclouxi hybrid population as control. Mating types were DZ (D × D), HD (H × D), HQ (H × Q), QD (Q × D), and QQ (Q × Q). Annual growth and wood properties were analyzed to evaluate suitability for central China's low mountain hills and elucidate growth advantages. Results indicate: (1) Survival rates ranked QQ > QD > HQ > DZ > HD. Except 2012 height, mating types showed highly significant (p < 0.01) differences in H and DBH across years, and significant differences (p < 0.05) in Pilodyn and modulus of elasticity (MOE). Mating type × block interaction was significant only for 2020 MOE. (2) H and DBH growth trends were similar; QQ and DZ had significantly larger increments. QQ showed the smallest Pilodyn (24.5 mm, highest density) and largest MOE (6.5 GPa). (3) Height and DBH (2012, 2016, 2020) showed significant (p < 0.05) or highly significant (p < 0.01) correlations, strongest between 2016–2020. DBH correlated negatively with Pilodyn and positively with MOE. 4)​​ Comprehensive Qi values ranked QQ (1.97) > QD (1.95) > DZ (1.85) > HD (1.80) > HQ (1.64), with QQ highest. Findings confirm QQ (C. bungei × C. bungei) is optimally suited for central China low mountain hills, providing support for Catalpa genetic improvement and economic utilization.

Somatic embryogenesis is pivotal for conifer propagation, yet its molecular basis remains poorly understood in gymnosperms. Single-nucleus RNA-seq offers unprecedented resolution for deciphering cell-type-specific transcriptional dynamics during gymnosperm embryogenesis. Here, we constructed a high-resolution transcriptomic atlas of Norway spruce (Picea abies) using high-efficiency and non/low-efficiency proembryogenic masses (HEMs and LEMs) collected before and after somatic embryo induction. Analysis of 55,635 nuclei identified 11 clusters, including somatic embryogenic cells (SCs) responsible for somatic embryo formation. Developmental trajectory analysis revealed a polarity-associated state S6 enriched in SCs, which was abundant in HEMs but nearly absent in LEMs. Key polarity genes, such as ROP-Guanine Exchange Factors, a homolog of PIN-FORMED 1, and PaWOX2, were enriched in the S6 state. Strikingly, overexpression of P. abies AGAMOUS-like 104 (PaAGL104), an S6-enriched transcription factor, induced excessive suspensor growth and apical-basal defects in both HEMs and LEMs embryos. TUNEL assays showed impaired suspensor elimination via suppressed programmed cell death in PaAGL104 overexpressors. Spatial expression analysis using a PaAGL104pro::NLS-mCherry reporter line revealed dynamic expression from ubiquitous to basal-enriched in the embryo proper. This region potentially contains the htube cell", a gymnosperm-specific stem cell crucial for suspensor formation and embryonic polarization. Our study identifies embryonic polarization as a key developmental checkpoint in conifer somatic embryogenesis and provides a high-resolution transcriptomic atlas of gymnosperm callus. These findings advance our understanding of totipotency in spruce and offer practical insights for improving clonal propagation in forestry.

Catalpa huangxin, a distinctive taxon within the genus Catalpa in China, is valued for its ornamental beauty and durable yellow heartwood. However, its wild populations are declining due to climate change and human activities, posing urgent conservation challenges. The unclear genetic diversity and population structure further complicate its protection and breeding efforts. To address these issues, this study employed RAD-seq to analyze 198 samples, including 169 C. huangxin, 24 Catalpa duclouxii, and 5 Catalpa ovata (outgroup), focusing on phylogeny, genetic diversity, gene flow, and dispersal routes. The results show that C. huangxin and C. duclouxii are distinct but closely related taxa. C. huangxin was divided into five subgroups with moderate genetic diversity (He = 0.2935, Ho = 0.4401). Subgroup 5 exhibited the highest diversity, but significant genetic differentiation (FST = 0.1983) was observed between subgroups, limiting gene flow and adaptation. Human activities, reproductive traits, and habitat fragmentation contribute to this differentiation. The study recommends in-situ conservation of genetically diverse subgroups, particularly Subgroup 5, artificial population restoration, germplasm banks, and expansion of its current distribution range. These strategies are essential for C. huangxin’s protection and genetic improvement, offering valuable insights for the conservation of other species with similarly restricted distributions.

This study integrated anatomic phenotype studies and genomic approaches to analyse morphological and anatomical variation, ecological adaptation strategies, and genetic regulatory mechanisms of needle leaves in 12 taxa of Keteleeria. Evaluation of 17 needle traits showed significant interspecific differences (p < 0.01) except for resin canals (constant 2) and epidermal thickness; epidermal thickness (coefficient of variation (CV)=1.151) and palisade tissue thickness (CV=1.167) presented the greatest degree of variation. Correlation analysis revealed significant cooperative variation between traits, such as between needle length and resin canal area, and between needle thickness and central cylinder thickness (p < 0.01). Cluster and principal component analyses divided the 12 taxa into 5 groups, which partially supported traditional geographical flora divisions but also suggested that molecular evidence should be combined to confirm the existence of controversial taxa. Environmental adaptability analysis revealed that epidermal thickening and central cylinder expansion could increase the water retention capacity to improve drought adaptation. A genome-wide association study (GWAS) identified 1957 significant SNP loci (-log(1)(0)P > 5) associated with 2058 candidate genes. A total of 682 genes associated with epidermal thickness were enriched in alkaloid biosynthesis (tropane, piperidine and pyridine alkaloid biosynthesis, and isoquinoline alkaloid biosynthesis) and sphingolipid metabolism pathways, which respond to precipitation seasonality. A total of 469 genes related to needle length were found to regulate asexual reproduction and thiamine metabolism, driven by temperature fluctuations. A total of 581 genes related to palisade tissue thickness were found to regulate cell division through microtubule cytoskeleton assembly and chromatin remodelling (such as the polycomb complex). Multiple trait-related genes (such as BDH, CCOMT, and At1g29880) constituted a multidimensional regulatory network for needle development. These findings provide a scientific basis for the systematic classification and conservation of Keteleeria and improve our understanding of the regulatory mechanisms of complex traits in Keteleeria plants at the molecular level.

Drought is a negative factor limiting tree growth and wood productivity of Catalpa bungei, a native species of the Catalpa genus in China that is characterized by high-quality timber and significant economic value. In the present study, stability analysis and comprehensive selection of elite clones of C. bungei were conducted based on gas exchange, wood growth, and hydraulic architecture at two sites with different rainfall levels. Tree growth and wood productivity of C. bungei were largely inhibited by rainfall shortage and the incongruity between rainfall and temperature. Some clones showed prominent wood productivity and fine wood properties at the Heze site, which experienced water deficit and seasonal drought. The high clone repeatability (R > 0.65) of these traits implies great potential for selecting drought-adaptive varieties. Specific clones with high stability in wood productivity and basic wood properties were selected based on BLUP-GGE biplot analysis. Elite clones (2–8, 2–6, 19–01, 1–3, 6–7, 008–1, and 22–03) with favorite wood growth and hydraulic safety were selected based on comprehensive assessment, and these clones are proposed for extension and cultivation in climate regions with limited rainfall. The outstanding growth performance of elite clones was attributed to their larger leaf area and great photosynthesis capacity per plant, rather than to a high photosynthetic rate per unit leaf area. Most of the elite clones exhibited timely adjustments in hydraulic architecture (vessel diameter and vessel density) between the drought season and the rainy season, which contributed to an effective trade-off between wood growth and hydraulic safety.

Catalpa lutea J.H.Wang, W.J.Ma & Z.Y.Li, a new species of Bignoniaceae from north, central, and east China, is described and illustrated. By combining recent morphological comparisons with phylogenetic analyses of nuclear single-nucleotide polymorphisms (SNPs) and the chloroplast genome, we demonstrate that C. lutea is readily distinguishable from its congeners, including Catalpa fargesii Bureau and other Chinese species of section Catalpa. A detailed morphological description, illustrations, and molecular data are provided. While conforming to sect. Catalpa in its typically ovate leaf blades, didynamous stamens, and five corolla lobes, C. lutea is unequivocally distinguished by its narrowly ovate crown, yellow heartwood, bright yellow anthers, filaments with purple dots, conspicuously thickened deep purple striations within the corolla tube, and floral spots exceeding 1 mm in diameter. Additional diagnostic characters include young foliage frequently flushed purple, mature leaves green with a purple tinge on occasion, and 3-4 nectaries at the leaf axils on the abaxial surface. The conservation status of this species is assessed as "Data Deficient" (DD) according to the IUCN Red List Categories and Criteria.

Toona sinensis is prized for its superior wood quality, ranking among the most important timber species. However, its growth and development has been severely constrained by persistent drought stress, which has become more frequent due to global climate change. Therefore, elucidating its drought response mechanisms and breeding high-yield, drought-resistant varieties are crucial for mitigating plantation productivity losses caused by global climate change. This study analyzed the effects of genotypic (G), environmental (E), and genotype-byenvironment (G & times;E) interactions on the growth, leaf morphology, anatomy, and S13C of T. sinensis clones in three test sites. We evaluated the key traits associated with drought response, and investigated the relationship between growth and drought resistance. The results revealed significant genotypic and G & times;E effects on volume. Leaf phenotypic variation was primarily determined by G & times;E effects, though leaf thickness and S13C exhibited significant genotypic effects. In severely water-deficient regions, clone volume significantly decreased, leaf area reduced, leaf thickness increased, and S13C markedly rose. Among leaf-related traits, S13C was identified as a key indicator of drought response, with its increase mainly attributed to enhanced leaf thickness due to palisade tissue thickening. Regression analysis showed no significant correlation between the comprehensive drought resistance index (based on leaf phenotypes) and volume. Thus, clones were evaluated separately across three test sites. On the basis of high volume, potentially drought-resistant clones were further screened (XC10-4 and XC15-3 for XT; XC6-17 and XC30-2 for HZ; XC15-3 and XC6-13 for LA), all achieving genetic gains in volume exceeding 20 %. These findings provide practical insights for the sustainable development of future T. sinensis plantations.

Abstract DNA methylation is important for many developmental processes. Its role in plant’s adaptation to light conditions, however, remains unclear. In this study, we examined the DNA methylomes of Norway spruce (Picea abies (L.) Karst.) under different light conditions, a combination of both light intensities (10, and 80 µmolm−2s− 1) and light qualities (with or without far-red light). The result showed that both light intensity and quality affected seedling growth, with the former playing a major role. Both light intensity and quality drove genome-wide methylation changes, which varied among cytosine contexts (CG/CHG vs. CHH). The changes in light quality and intensity yielded a similar number of differentially methylated regions (DMRs), but light intensity was a major contributor in gene expression changes. At the genome-wide level, DNA methylation changes showed no consistent correlation with gene expression alterations. However, a subset of genes—particularly those involved in photosynthesis and circadian rhythms—exhibited coordinated methylation and expression changes, suggesting context-specific regulatory links. The findings indicate that DNA methylation may directly modulate photosynthesis and photoperiod genes and trigger an epigenetic memory, which in turn affects growth of Norway spruce seedlings in response to light conditions. In sum, our study provides a global picture of DNA methylation and gene expression under different light conditions in conifers and thus paves a way for future studies of light-directed gene regulation in plants.

Silver nanoparticles (AgNPs) are known for their broad-spectrum antimicrobial activity and offer distinct advantages as antimicrobial agents, including high efficacy and low tendency for resistance development. However, the mechanisms by which AgNPs inhibit plant fungal pathogens remain unclear, particularly in anthracnose caused by Colletotrichum gloeosporioides. Therefore, it is essential to elucidate the antifungal mechanisms of AgNPs against this pathogen. In this study, we demonstrated that AgNPs effectively inhibit mycelial growth and spore germination of C. gloeosporioides at concentrations of 5mgL−1 and 20mgL−1. Mechanistic investigations revealed that AgNPs suppress the expression of genes related to reactive oxygen species (ROS) scavenging and cell wall integrity, rather than causing disruption of cell membrane integrity. Furthermore, AgNPs treatment significantly reduced anthracnose disease severity in Catalpa bungei leaves. Additional results indicated that AgNPs may enhance ROS burst in C. bungei by up-regulating the expression of RBOH genes, which in turn promote the expression of pathogenesis-related (PR) protein genes. Collectively, these findings clarify the potential mechanisms of AgNPs antifungal activity and provide a theoretical basis for their practical application in the management of anthracnose, as well as for resistance breeding in forestry timber species.

Toona sinensis is a high-value cultivated timber tree for which efficient clonal screening across heterogeneous environments is important. We evaluated whether two nitrogen-normalized phenotypic indices provide useful information beyond their component traits: a structural index (S-NNI = LMA/LN) and a height index (H-NNI = H/(LN+RN)). Eighteen clones were tested at three field sites in China (Lu’an, Heze, and Xingtai). Validation combined algebraic-coupling diagnosis, allometric tests, agreement with non-ratio residuals, external criterion validity, grouped leave-one-clone-out cross-validation, and within-site rank changes. S-NNI agreed strongly with the non-ratio LMA residual (ρ = 0.734, 95% CI = 0.559–0.830) and was positively associated with site-adjusted palisade tissue thickness (ρ = 0.313, 95% CI = 0.031–0.581). For leaf thickness and palisade tissue thickness, the S-NNI model produced the highest leave-one-clone-out R² values among six candidate models (0.176 and 0.163, respectively), although its RMSE advantage over the site-only and quadratic models was uncertain. H-NNI showed moderate agreement with the non-ratio height residual (ρ = 0.478) and site-adjusted DBH (ρ = 0.576), increasing DBH prediction R² from 0.865 in the site-only model to 0.913. However, additive and interaction models retaining H, LN, and RN performed better, and H-NNI provided no independent information after adjustment for its components. Within-site rankings changed most for S-NNI in Xingtai and H-NNI in Heze. S-NNI may therefore serve as a parsimonious preliminary descriptor of leaf structural phenotype, whereas H-NNI should be restricted to exploratory detection of ranking discordance. Neither index represents nitrogen-use efficiency or replaces production traits, direct component analysis, or multi-environment stability assessment.

Salt stress severely constrains growth and wood quality in woody plants. Although non-specific lipid transfer proteins (nsLTPs) are known to participate in stress responses, their function in the valuable timber species Catalpa bungei remains largely unexplored. Here, we characterized CbLTP67, a guard cell-enriched gene whose expression is downregulated by both salt stress and salicylic acid (SA). Overexpression of CbLTP67 resulted in excessive accumulation of reactive oxygen species (ROS), weakened antioxidant capacity, and reduced survival under salt stress. Specifically, CbLTP67 overexpression impaired stomatal closure following salt treatment, whereas exogenous SA application restored normal stomatal aperture and mitigated salt-induced damage. Time-resolved transcriptomic analysis showed that differentially expressed genes (DEGs) were significantly enriched in pathways related to SA signaling and stomatal movement. Moreover, yeast two-hybrid and bimolecular fluorescence complementation (BiFC) assays identified CbRD19A and CbPAT12 as specific interacting partners of CbLTP67 at the plasma membrane. Both proteins were induced by salt stress. Interestingly, CbLTP67 contains three predicted palmitoylation sites that are absent in CbRD19A. Together, our findings support a novel CbPAT12-CbLTP67-CbRD19A regulatory module that negatively modulates salt tolerance by disrupting SA-mediated stomatal closure in C. bungei.

To overcome the seasonal constraints of explant availability and facilitate genetic improvement in Catalpa ovata, this study established a dual-pathway in vitro regeneration system (encompassing adventitious shoot organogenesis and somatic embryogenesis) using mature zygotic embryos. We systematically evaluated the synergistic effects of maternal genotypes, plant growth regulators (PGRs), basal media, and the histone deacetylase inhibitor Trichostatin A (TSA). Genotype screening revealed significant divergence in regenerative potential, with the half-sib family 32F17 exhibiting superior responsiveness (84.7% callus induction). A high cytokinin-to-auxin ratio (ZA3 medium) optimally drove direct shoot organogenesis. For adventitious shoot proliferation, the addition of TDZ significantly improved the multiplication coefficient (up to 2.99 on ZB4 medium), although a physiological trade-off with shoot elongation was observed. In parallel, the application of 10 µM TSA significantly enhanced somatic embryogenesis from embryogenic calli, effectively alleviating the inhibitory constraints of exogenous PGRs. For rhizogenesis, the DKW basal medium proved superior to half-strength MS, with the ZE3 treatment (0.1 mg·L−1 NAA + 0.1 mg·L−1 IBA) yielding the highest rooting frequency (69.6%) and robust root architecture. Notably, while somatic embryo conversion remained recalcitrant, plantlets derived exclusively from the adventitious shoot organogenesis pathway were successfully acclimatized ex vitro. These transplanted plantlets exhibited consistently high survival rates (83.1–84.4%) across all tested genotypes, effectively overcoming the initial genotype-dependent recalcitrance. Collectively, this optimized protocol provides a reliable technical platform for the large-scale clonal propagation and biotechnological breeding of C. ovata.

Toona sinensis (TS), a multipurpose tree widely cultivated across Asia to Australia, is an attractive novel fodder resource. However, its effects on meat quality and underlying mechanism remain largely unknown. Therefore, black goats were fed fermented TS (Test) or conventional silages for 90 days to evaluate its effects on growth, meat quality, and rumen microecology. TS supplementation caused no adverse effects and significantly enhanced daily weight gain. Meat from TS-fed goats exhibited enhanced umami and saltiness (E-tongue) and a fresher aroma (E-nose, sensory evaluation), with fewer undesirable volatiles (SPME-GC-MS). TS significantly (p < 0.05) elevated the accumulation of n-3 polyunsaturated fatty acids, and minerals (especially Sn) in the meat, while reducing bitter-tasting arginine. Rumen fermentation remained stable, but TS significantly (p < 0.05) increased rumen pH, microbial diversity, Firmicutes/Bacteroidota (F/B) ratio, and microbial protein content. Correlation network analysis identified rumen microbial diversity and F/B ratio as key drivers linking growth and meat flavor. Furthermore, OPLS-DA analysis confirmed that E-nose, E-tongue, and mineral (Sn, Ni, Se) profile can effectively discriminate TS-fed goat meat. These findings suggest that fermented TS represent a promising functional feed for enhancing both flavor and nutritional quality of goat meat.

Global warming is reshaping the spatial niches and productivity of forest resources, challenging the reliable supply of high-value timber. Catalpa fargesii and Catalpa lutea are two colored-wood species with outstanding ornamental and mechanical properties, showing strong potential for industrial timber production in China. However, the long-term "use-over-management" approach has resulted in rapid resource decline and insufficient understanding of their climatic adaptability. In this study, the MaxEnt model was applied to predict the current and future (2050s-2070 s) potential suitable habitats of both species under two climate scenarios (SSP1-2.6 and SSP5-8.5), integrating climatic, edaphic, and topographic variables Temperature (bio 6, bio 9) and precipitation (bio 12, bio 14) emerged as the principal climatic controls, with soil base saturation and terrain heterogeneity further shaping suitability. Currently, C. fargesii is centered in the Loess Plateau-Qinling-Taishan (44.52 & times; 10(4) km & sup2;), whereas C. lutea occupies the eastern warm-temperate belt (30.57 & times; 10(4) km & sup2;). Under climate change both show a "contraction and expansion" pattern, but responses diverge: C. fargesii remains stable with minor centroid shift, while C. lutea is climate-sensitive, showing a about 10.03 & times; 10(4) km & sup2; contraction (2050 s, SSP1-2.6) followed by a similar to 48% expanding compared with the current suitable area (2070 s, SSP5-8.5), with centroid moving present to NE to SE-signaling distinct niches and actionable zoning. These results provide an operational, spatial basis for the sustainable cultivation, targeted introduction, and clonal propagation of Catalpa species. By supporting stable domestic raw-material supply chains and high-value timber industries, this study contributes to the development of climate-resilient and economically sustainable forestry in China.

Catalpa bungei is a valuable timber species famous for its high-quality wood properties, which are greatly compromised by tension wood (TW) formation. However, the molecular mechanisms underlying TW remain unclear. In this study, we identified that CbuMYB27 was specifically upregulated during TW formation in C. bungei. CbuMYB27 exhibits the highest expression level in the stem and its encoded protein possesses transcriptional activation activity. Overexpression of CbuMYB27 in hybrid poplar (84K) resulted in increased cambium layers and xylem width. Further analysis revealed that CbuMYB27 negatively regulates lignin biosynthesis. Molecular analysis indicated that CbuMYB27 positively regulates cambial activity and negatively regulates lignin biosynthesis by directly activating cambium-related genes and suppressing lignin-biosynthetic genes, respectively. Protein interaction assays indicated that CbuMYB27 physically interacts with a bHLH transcription factor, CbuBIM1. Although CbuBIM1 cannot directly regulate the target genes of CbuMYB27, it antagonizes CbuMYB27-mediated transcriptional regulation of these downstream genes. Moreover, CbuBIM1 attenuates the promoting effect of CbuMYB27 in TW formation caused by bending stress. In summary, our findings identify a functionally antagonistic module of CbuMYB27- CbuBIM1, which is involved in TW formation by modulating cambium activity and lignin biosynthesis in C. bungei and thus provides a potential target for the improvement of wood quality in C. bungei.

Catalpa bungei is a precious timber species endemic to China, and its congeneric species Catalpa lutea possesses higher economic value due to its distinctive golden-yellow heartwood. To elucidate the metabolic and molecular mechanisms underlying the heartwood color difference between C. lutea and C. bungei, as well as the potential associations between heartwood color and wood properties, we conducted metabolomic and transcriptomic analyses on the sapwood, transition zone, and heartwood of 21-year-old C. bungei and C. lutea trees, and systematically evaluated their wood anatomical structure, physical and mechanical properties, and decay resistance. The results showed that compare with C. bungei, 17 chromogenic metabolites (ten quinones, six flavonoids) were significantly accumulated in the heartwood of C. lutea, among which α-lapachone derivatives (especially 9-hydroxy-α-lapachone and 4,9-dihydroxy-α-lapachone) accounted for 69.99% of the total chromogenic substances, representing the major color-contributing compounds in C. lutea heartwood. Through GO enrichment analysis and expression profiling, five CbuCYP450 genes with hydroxylation functions, namely CbuCYP86A1 (evm.TU.group330.7), CbuCYP82A3A (evm.TU.group3.584), CbuCYP82A3B (evm.TU.group3.585), CbuCYPH3 (evm.TU.group11.1088), and CbuCYP71D95 (evm.TU.group11.1150), respectively, were identified as highly expressed in the transition zone of C. lutea, potentially involved in the hydroxylation steps of α-lapachone derivative biosynthesis. Wood property measurements revealed that, compared with C. bungei, C. lutea possessed significantly higher double wall thickness and wall-to-lumen ratio in fiber cells, as well as significantly superior wood density, hardness, compressive and tensile strengths, and natural decay resistance. Collectively, whose biosynthesis may be associated with the high expression of CbuCYP71D95 and other CbuCYP450 genes. Furthermore, the anatomical structure characterized by thick-walled and narrow-lumened cells, together with the abundant secondary metabolites, jointly endow C. lutea with excellent mechanical properties and decay resistance. This study provides a theoretical foundation for the color-targeted breeding of C. bungei and C. lutea and for the high-value genetic improvement of precious timber species.

Sophora moorcroftiana, a key stone shrub in Xizang (Tibet), has significant ecological and economic value. However, its populations face severe degradation. Understanding key evolutionary drivers of genetic variation within and among populations is critical for conserving and managing this species. Previous studies indicate a strong genetic structure correlated with altitude, but limited knowledge exists about the drivers of its geographic structure and evolutionary history. To address this, we conducted genomic research on 225 samples from 15 populations of S. moorcroftiana. Populations of S. moorcroftiana exhibited distinct population structure, divided into four subpopulations. Subpopulation P1 (Gongbu Jiangda County, Nyingchi) showed the greatest genetic differentiation from other populations (average Fst = 0.2477), with the lowest genetic diversity (Pi = 1.1 × 10−4) and the smallest effective population size. P2, in the lower altitude area (Nyingchi), had larger genetic differentiation from the mid–altitude P3 (Fst = 0.168) and the high–altitude P4 (Fst = 0.227), with lower genetic diversity and effective population size. P3 and P4 had smaller genetic differentiation, with P3 having the largest genetic diversity and effective population size, followed by P4. D–statistics and Treemix revealed predominant gene flow from lower to higher altitude populations, with geographic proximity enhancing genetic sharing. SMC + + analyses suggested that the subpopulations experienced severe bottlenecks, genetic drift, and population expansion due to glacial–interglacial cycles and geological events. Partial Mantel tests revealed that the genetic variation distribution of S. moorcroftiana populations was more influenced by geographic isolation. Through genotype–environment association analysis, 90 single nucleotide polymorphisms (SNPs) were found to be significantly associated with environmental factors, of which 55 SNPs were annotated to genes, involving 20 genes. The uplift of the plateau and intense climatic fluctuations during the Quaternary have profoundly impacted the genetic structure and geographic distribution of species in the region. The current genetic distribution characteristics were shaped by the subsequent influences of geography, environment, and gene flow. These findings provide a theoretical basis for the utilization of genetic resources, the formulation and implementation of conservation strategies for S. moorcroftiana, and the exploration of its adaptation mechanisms to the plateau environment.

Understanding the flowering of woody plants is crucial for controlling flowering time and shortening breeding cycles, yet the mechanisms are largely unknown. APETALA2/ethylene response factor (AP2/ERF) transcription factors are essential in floral transition and development. We report an early-flowering (EF) variety of Catalpa bungei that blooms in its planting year, whereas normal-flowering (NF) requires 5-7 years. This study identified 150 CbuAP2/ERF genes in the C. bungei genome, categorized into 4 subfamilies and 17 groups. Expression analysis showed AP2/ERF genes mainly activated during the vegetative to mixed buds transition and predominantly expressed in the stem. To explore CbuERF roles in floral transition, six genes (CbuERF3B/060/071/RAP2-3/114/003-4) induced by floral induction were selected. CbuERF114 expression differed significantly during the reproductive transition between NF and EF. Subcellular localization and transcriptional activation analysis indicated that CbuERF114 is a nuclear protein with a C-terminal transcriptional activation domain. Overexpressing CbuERF114 in Arabidopsis (OE-CbuERF114) delayed bolting and flowering by about 4 days but extended the flowering period, increasing the maximum flowering growth rate by 54.25% and the number of flowers by 58.00%. CbuERF114 inhibited flowering onset but enhanced flowering rate and quantity. These findings advance our understanding of CbuAP2/ERFs in phylogeny, structure, expression, and function, highlighting their importance in the floral transition of woody plants.