Populus deltoides is a key species for industrial timber and ecological construction in temperate regions, where increasingly frequent and persistent heat waves pose serious challenges to its survival. However, the epigenetic mechanisms by which DNA methylation regulates environmental responses remain poorly understood. Here, whole-genome bisulfite sequencing and RNA-seq were performed on five P. deltoides genotypes grown in temperate and tropical regions. Results revealed that CG/CHG methylation stability is closely correlated with environmental sensitivity. Significant CG/CHG methylation variations may occur specifically in sensitive genotypes with large provenance-environment differences, thereby threatening the survival of P. deltoides by inhibiting the expression of key genes involved in life processes. CHH methylation variation may act as a potential epigenetic regulator of environmental adaptation. Promoter CHH-hypermethylation appears to represent a general response of P. deltoides under high-temperature and short-photoperiod (HS) stress, potentially regulating the expression of 56 genes to activate Ca2+ influx and heat shock proteins, repressing auxin, cytokinin, and cell cycle pathways, thereby initiating stress-protective responses. PdeCNGC13, PdeARF6, PdeLOG3, and PdeHSP15.7 were identified as potential regulatory genes of HS adaptation that are associated with DNA methylation. The mechanism of PdeLOG3 may involve HS-induced CHH-hypermethylation at its PdeLOG3 promoter, which may be associated with suppressed expression, reduced dihydrozeatin levels, and growth. This effect was partially reversed by 5-Azacytidine administration, accompanying increased cytokinin synthesis, enhanced antioxidant capacity, and coinciding with alleviation of HS stress. Our work preliminarily reveals the molecular mechanisms underlying DNA methylation-associated environmental adaptation in poplar, providing potential genetic targets for breeding climate-resilient trees.
Biogenic volatile organic compound (BVOC) emissions are pivotal in plant-environment interactions, yet their intrinsic linkages with photosynthesis and leaf economics across diverse tree species remain poorly integrated. This study investigated seven subtropical broadleaf species spanning distinct lineages to unravel how BVOC chemotypes (isoprene- vs. monoterpene-dominance) align with photosynthetic energy use and leaf structural traits. Using controlled measurements on excised branches to isolate physiological relationships, we combined TD-GC-MS, gas-exchange, and leaf trait analyses. The results revealed strong divergence in BVOC chemotypes that was broadly coherent with species phylogeny and ecological strategy. Isoprene-dominant (ISO) species exhibited higher photosynthetic rates (A), greater electron transport capacity (J max), and elevated J max/V cmax ratios, consistent with the hypothesis that isoprene synthesis functions as a photosynthetic overflow mechanism for energy dissipation. In contrast, monoterpene-dominant (MTS) species displayed higher specific leaf weight (SLW) and relied on stored and induced emissions, reflecting a conservative, defense-oriented strategy. BVOC profiles were strongly correlated with SLW and photosynthetic capacity, highlighting a coordinated 'structure-function-volatile' adaptive syndrome. These findings suggest that BVOC emissions may be embedded within leaf economic strategies and photosynthetic networks, providing a basis to help refine next-generation BVOC models by integrating leaf structural traits (e.g., SLW) and photosynthetic electron transport capacity (J max) into model parameterization.
24-nt siRNA-directed DNA methylation is crucial for heterosis in herbaceous plants, but its regulatory function, particularly 24-nt phasiRNA (phased small RNA)-mediated DNA methylation, remains unexplored. This study analyzed whole-genome DNA methylation and small RNA expression between high-growth (H2) and low-growth (L3) Populus deltoides hybrids and their parents, investigating how 24-nt phasiRNA-associated DNA methylation contributes to heterosis. Methylation levels in hybrids and parents ranged from 11.30% to 12.30%, with 22.27% to 23.34% of methylation sites being hybrid-specific. Differentially methylated regions (DMRs) between hybrids and parents mainly originated from similarly methylated regions in parents. Hypo-DMRs were more prevalent in H2, which was the opposite in L3. In the promoter region, expression of differentially methylated genes was correlated with DMR methylation levels between hybrids and parents, albeit exhibiting opposite trends in H2 and L3. Approximately 9% of 24-nt phasiRNAs in hybrids showed additive, dominant, or over-dominant inheritance, with H2 showing paternal bias and L3 maternal bias. 24-nt phasiRNAs were positively correlated with promoter CHG/CHH-DMR methylation levels and negatively correlated with non-additive gene expression, which may facilitate heterosis formation. Gene expression associated with 24-nt phasiRNAs-linked DNA methylation in hybrids was distinctly different, with H2 mainly showing high 24-nt phasiRNA expression, hyper-DMRs, and decreased gene expression, while L3 mainly showed low 24-nt phasiRNA expression, hypo-DMRs, and increased gene expression. We identified 13 candidate 24-nt phasiRNAs and seven key genes, specifically involved in nitrogen response (NLP2/NLP8-like) and photosynthesis (PsbP), which may play an important role in heterosis. This study provides the first evidence of 24-nt phasiRNA-associated DNA methylation in tree heterosis, offering novel insights into epigenetic modifications.
Tree stem taper varies dynamically with tree size due to biomechanical constraints governing stability, yet capturing this size-dependent shape plasticity remains a challenge in forest biometrics. Traditional variable-exponent models impose rigid functional forms, while emerging machine learning approaches often obscure these biological relationships within black-box structures. Furthermore, previous applications of generalized additive models (GAMs) have predominantly focused on additive effects, overlooking the critical interactions between tree size and relative position along the stem. To address this gap, we investigated whether explicitly modeling the nonlinear interactions between tree size and relative height could resolve systematic biases in taper prediction. Using a dataset of 516 felled Chinese fir (Cunninghamia lanceolata) trees, we constructed GAMs incorporating tensor product interaction smooths and benchmarked them against the widely used parametric models and two machine learning algorithms. We found that GAMs relying solely on main effects failed to outperform the parametric benchmark. However, introducing explicit interaction terms, specifically between diameter at breast height and relative height, substantially reduced the root mean square error by 52.3% compared to the additive GAM and surpassed both the established Kozak-II benchmark and the optimized machine learning models in validation accuracy. Variable importance analysis confirmed that these interactions act as critical modifiers that drive the model improvement by accurately capturing the ontogenetic drift in stem form, such as the pronounced basal flare in larger trees. These findings demonstrate that interaction-inclusive GAMs serve as a powerful tool to bridge the trade-off between algorithmic flexibility and parametric interpretability, offering a biologically grounded approach for precision forest inventory.
Plant thorns represent a prominent evolutionary innovation formed through millions of years of natural selection. However, thorn structures greatly restrict the cultivation and management of many economically important crops, making the breeding of thornless varieties a key objective in modern agricultural breeding. Although different plant species possess apparently similar sharp appendages, these structures originate from different plant organs or tissues. Thorns are not merely mechanical defense structures but are the result of evolutionary adaptations by plants to cope with herbivore pressure and abiotic stresses over evolutionary time. Thorn morphogenesis integrates multiple pathways involved in developmental regulation, defense signaling, and environmental perception, reflecting the resource allocation trade-offs between growth investment and defense efficiency in plants. This review provides a comprehensive synthesis of the developmental origins, anatomical diversity, and ecological defense functions of plant thorns. By integrating paleobotanical evidence, this review traces the evolutionary emergence of thorns during the Paleogene and Neogene periods and reveals the adaptive associations between thorn diversification and the radiation of large herbivorous mammals. At the molecular level, this review focuses on recent advances in developmental genetics, with an emphasis on the regulatory networks underlying thorns' development, as well as the regulatory roles and crosstalk mechanisms of phytohormone signaling pathways involved in defense, including jasmonic acid and gibberellin, in thorns' development. Through a multidisciplinary perspective, this review provides a synthesis of current knowledge on the origin, diversification, and environmental adaptive significance of thorns, providing new insights into the developmental plasticity of plant defense structures.
Broadleaved Korean pine forest, a typical zonal vegetation type in Northeastern China, is important in maintaining regional ecological security. However, the regeneration of Korean pine (Pinus koraiensis) seedlings remains a major constraint in the primary forests. Although declining light availability and increasing soil pathogens are recognized as critical factors affecting seedling survival and growth, their interactive effects and underlying mechanisms remain unclear. In this study, we conducted a controlled experiment with three light levels (200, 400, and 600 μmol·m-2·s-1) and four soil pathogen concentrations (0, 1 × 104, 1 × 106, and 1 × 108 CFU/mL) to examine seedling survival, growth, physiology, and above- and belowground functional traits. Low light significantly reduced survival, relative growth rate, photosynthesis, and biomass of P. koraiensis seedlings, while the presence of high pathogen concentrations exacerbated these impacts, notably driving mortality rates up by 95%. Leaf traits were only regulated by light, with shaded conditions increasing specific leaf area and nitrogen (N) concentration, but decreasing total phenolics and carbon/nitrogen ratio. In contrast, root traits were jointly influenced by light and soil pathogens. Under low light, seedlings exhibited an acquisitive strategy characterized by higher specific root length and N concentration, along with reduced root diameter and defense investment. However, increasing pathogen concentration reversed this pattern, suppressing resource acquisition traits while enhancing root diameter and defensive compounds (total phenolics and tannins). These results indicate that light determines the baseline resource context, while soil pathogens impose additional constraints that shift root strategies from resource acquisition to defense. Such interactive regulation modulates seedling establishment, with critical implications for improving forest regeneration and ecosystem stability.
The model woody plant Populus trichocarpa displays an atypical alkene-diverse wax cuticle likely driven by copy number variation (CNV) of 3-ketoacyl-CoA synthases (KCS), which has been difficult to confirm with short-read assemblies. Long-read sequencing enables the development of telomere-to-telomere resources to detect cryptic variation, including CNVs, which are currently missed. Integrating this information can improve genomic prediction for breeding and provide insights into the evolutionary basis of important traits. Our analysis of 78 long-read haplotypes from chromosome 10 identified more than twice as many KCS genes as previously reported, and numerous intragenic non-synonymous substitutions. Random Forest predictive models highlighted the importance of Potri.010G079500 in producing very long chain alkenes; however, its absence did not predict previously reported alkene-deficient phenotypes. Instead, alkene levels are best predicted by the combinations of KCS copies. Additionally, amino acid substitutions clustered around ligand and donor binding pockets, suggesting they contribute to differing wax cuticle composition. Finally, each KCS gene and copy was linked to a Helitron transposon. A phylogenetic analysis suggests Helitrons are the evolutionary mechanism for generating KCS tandem arrays. Long-read generated telomereto-telomere assemblies of P. trichocarpa chromosome 10 revealed large-effect loci critical to genetic studies that are unattainable from short-reads. This new resource produced novel insights into genome structure and function, and a novel mechanism for generating tandem gene duplication. Our results highlight that, given current challenges in annotation and assembly, detailed and focused long-read sequences are key to interpreting complex genomic regions that contain tandem copy number variants.
Genetic exchanges underpin population adaptation and species evolution. However, knowledge of the genetic impacts of historical, anthropogenic crop-to-wild gene flow remains limited. In southwestern China, the long cultivation and parapatric distribution of Juglans regia and J. sigillata provide an ideal system to investigate this process, yet the evolutionary origin of the cultivated walnut in this region remains a mystery. Using 31 microsatellite loci to genotype 2,866 individuals, along with 716 chloroplast genomes, we evaluated genetic diversity, population structure, and maternal lineage patterns across the region. Population demographic histories were subsequently inferred using approximate Bayesian computation. Our analysis revealed that J. sigillata has higher genetic diversity than J. regia, attributed to its long-term persistence in heterogeneous environments. We observed extensive hybridization between the two species around the Sichuan Basin, forming two geographically distinct subgroups: Hybrid1 in the northwest and Hybrid2 in the south. Both subgroups exhibit variable parental contributions, but with the chloroplast genome entirely introgressed from J. regia. Furthermore, the Sichuan Basin and Yangtze River acted as major geographic barriers to north-south gene flow. Our divergence time estimates showed that the two species diverged during the Pleistocene, followed by an admixture event between J. regia and J. sigillata, forming Hybrid2 during the early Holocene. Subsequent admixture between Hybrid2 and J. regia produced Hybrid1 during the middle Holocene. We propose that cultivated walnuts in southwestern China originated through introgression between J. regia and wild J. sigillata during the Holocene, prior to the introduction of agriculture to the region, a process likely facilitated by historical southward human migrations. This research elucidates how long-term human influence has subtly reshaped the genetic landscape of walnuts in southwestern China through gene flow, providing valuable insights for the study and management of other tree crops.
The widespread decline and mortality of the Three-North Shelter Forest under climate change is threatening the sustainability of arid and semi-arid ecosystems. As the dominant tree genus in these shelterbelt forests, poplars (Populus spp.) display clear varietal differences in decline patterns, yet the underlying physiological mechanisms remain poorly understood. To address this question, we compared two poplar varieties, Populus alba var. bachofenii (P.b) and Populus alba var. pyramidalis (P.p), using branch samples from upper and lower canopy positions. The results showed that although hydraulic conductivities (K s and K l ) did not differ significantly between varieties, P.b consistently exhibited lower percent loss of conductivity (PLC), particularly in the upper canopy branches. In contrast, P.p experienced more negative midday water potentials (Ψ md) in the upper crown, indicating greater water deficit. Within P.p, declining individuals (P.p-D) displayed higher PLC, whereas hydraulic conductivity, predawn water potential (Ψ pd), and non-structural carbohydrates (NSC) concentrations were similar to those of healthy trees, indicating that dieback was associated primarily with increased hydraulic vulnerability, rather than reduced transport capacity or carbon depletion. Tree-ring analyses further revealed stable growth in P.b, whereas P.p was more drought-sensitive and showed greater interannual variability. Trees with higher PLC exhibited greater growth sensitivity and reduced radial growth rates, supporting the hydraulic limitation hypothesis. Overall, this study clarifies the physiological mechanisms underlying the contrasting decline patterns among poplar varieties in water-limited regions, and provides guidance for optimizing species selection and management strategies in arid shelterbelts.
Climate change poses a significant threat to biodiversity, highlighting the urgent need to understand species' adaptive potential. Using the sky island limestone-endemic shrub Lonicera oblata in North China as a model, we integrated genomic, transcriptomic, and metabolomic analyses to investigate its evolutionary trajectory. The assembled genome is 786.92 Mb in size, and it has the highest proportion of repetitive sequences (66.47%) in Lonicera. Multiple expanded gene families were enriched in pathways related to stress response, including oxidoreductase activity, cell wall synthesis, and energy metabolism. The bHLH gene family exhibits both a significant expansion in the comparative genomic analysis and a convergent transcriptional activation under calcium stress, correlating with the metabolic reprogramming of organic acid synthesis and ion homeostasis. We detected low genetic diversity (π: 2.24e-3 to 2.80e-3), high differentiation (average fixation index: 0.16), drastic historical decline, and strong genetic load among populations. Notably, the northeasternmost and most recently diverged population (Jiankou) exhibited extreme inbreeding but the lowest genetic load, suggesting that genetic purging enhances small population survival. The genotype-environment association analysis identified 1,286 core SNPs potentially correlated with local adaptation. Genomic offset projections predicted high maladaptation risk under future climates, especially in eastern and southern populations. This study provides essential insights into the mechanisms of local adaptation, genomic vulnerability, and climate resilience of threatened sky island species, and offers guidance for targeted conservation strategies.
Mangrove ecosystems function as vital biogeochemical interfaces between terrestrial and marine environments, playing a crucial role in transforming heavy metals (HMs). However, this ecosystem is heavily impacted by climate change and anthropogenic activity, including an increase in HM toxicity. The current review synthesizes understanding of HM transformation across three interconnected levels: tidal dynamics, rhizosphere processes, and plant adaptation strategies. Initially, tidal inundation affects the distribution, speciation, and mobility of HMs by altering sediment biogeochemical properties, including pH, redox potential, salinity, and microbial activity. Further, tidal effects influence metal immobilization and remobilization, thereby impacting HM behavior within the rhizosphere, which serves as a secondary barrier to metal transport. Activities in the rhizosphere, including the presence of microbes, generate redox micro-gradients, and release organic ligands that facilitate metal complexation, precipitation, and detoxification. The synergistic interactions between roots and microbes support rhizoremediation in mangrove systems, lowering HM toxicity, and enhancing sediment stability. Additionally, mangroves employ various structural, physiological, and biochemical strategies, including selective metal uptake, excretion, internal detoxification systems, and the activation of antioxidant enzymes, to reduce HMs-induced stress. However, adaptation mechanisms differ among species and are influenced by interactions between tidal regimes, rhizosphere conditions, and plant traits. Integrating the three hierarchical levels—tide, root, and plant—highlights that mangrove ecosystems function as self-regulating biogeochemical systems capable of stabilizing and transforming HMs under dynamic environmental conditions. Such integrative mechanisms advance nature-based remediation strategies and reinforce mangroves' role as effective natural barriers against HM pollution, thereby contributing to sustainable coastal management and ecosystem resilience in a changing global environment.
Drought is a major abiotic stressor that severely threatens forest tree growth and survival worldwide. The SQUAMOSA promoter binding protein-like (SPL) family is a group of plant-specific transcription factors that play important roles in plant growth, development, and environmental adaptation. Our study showed that overexpression of Fraxinus mandshurica SPL2 (FmSPL2) promotes lignin biosynthesis and enhances drought tolerance. Phenotypic analysis indicated that the stomatal aperture of FmSPL2-OE1 and FmSPL2-OE2 was reduced by 12.05% and 19.23%, respectively, compared to the wild type (WT). Additionally, the xylem width of the sixth internode in these lines increased by 26.07% and 25.93% relative to WT. Correspondingly, lignin content was elevated by 19.87% and 18.48% compared with WT, respectively. Under drought stress, the lignin content in FmSPL2-OE plants remained elevated compared to WT. Furthermore, the overexpression lines exhibited increased SOD and POD activities, accompanied by reduced levels of MDA, H2O2, and superoxide anion. Transcriptome analysis indicated significant upregulation of multiple genes involved in phenylpropanoid biosynthesis in FmSPL2-OE plants, including phenylalanine ammonia-lyase (PAL), cinnamyl alcohol dehydrogenase (CAD), and 4-coumarate-CoA ligase (4CL). Moreover, the yeast one-hybrid and dual-luciferase reporter assays demonstrated that FmSPL2 directly binds to the promoter regions of phenylpropanoid-related genes like PAL, CAD, and PRX, thereby activating the expression of these genes and enhancing lignin biosynthesis. These results elucidate a novel function of FmSPL2 in enhancing drought tolerance through the regulation of phenylpropanoid pathway-mediated lignin accumulation.
The interplay between historical biogeography and environmental selection shapes the genetic architecture of species; however, their relative contributions in widespread and ecologically important tree species remain poorly understood. In the Sino-Japanese Floristic Region, the East China Sea has alternately acted as a barrier and a corridor during glacial-interglacial cycles, influencing species isolation and contact. However, the extent to which these historical dynamics, along with environmental gradients, have driven adaptive evolution in dominant forest trees remains unresolved. In the present study, we integrated phylogeographic reconstruction and landscape genomics based on whole-genome resequencing data from 171 individuals across 35 populations to investigate the evolutionary history and adaptive mechanisms of Quercus gilva, a keystone evergreen oak, in East Asian subtropical forests. Population genomic analyses revealed two deeply divergent genetic groups: the China group and the Japan-Korea group, and demographic modeling indicated that their divergence dates back to the Miocene epoch. The relatively high genomic diversity of Q. gilva may result from the absence of severe genetic bottlenecks throughout its evolutionary history, multiple microrefugia during the glacial periods, and postglacial secondary contact. Notably, Quaternary glacial cycles repeatedly facilitated gene flow and admixture between these groups via exposed land bridges. Landscape genomic analyses further demonstrated that adaptive divergence in Q. gilva is shaped by both geographic isolation and environmental gradients, with annual precipitation emerging as the primary climatic driver. This study provides a genome-wide perspective on how historical biogeography and environmental selection interact to shape the genetic architecture of a dominant subtropical evergreen forest species, offering novel insights into the evolutionary dynamics and adaptive evolution across East Asian biodiversity hotspots.
Members of the bZIP transcription factor family play critical roles in plant salt adaptation. In this study, transgenic poplar lines with overexpression (OE) and RNA interference (RNAi) mediated suppression of PagbZIP60 were generated to investigate its function. Under salt stress, OE lines exhibited reduced growth, whereas RNAi lines showed improved performance. Increased superoxide dismutase (SOD) activity, electrolyte leakage rate, Na+ levels, malondialdehyde and hydrogen peroxide (H2O2) contents, but decreased peroxidase (POD) and catalase (CAT) activities, and anthocyanin content were revealed in OE lines compared with those in wild-type poplar (WT). OE lines also presented reductions in leaf number and area, increased stomatal density and aperture, and diminished photosynthetic rate and water utilization efficiency (WUE), leading to a lower capacity for carbon assimilation. PagbZIP60 was found to decrease salt tolerance and carbon sequestration capacity by impairing reactive oxygen species (ROS) scavenging and photosynthesis through negatively regulating the expression of downstream genes (TT7, PMEI, MLP, SAUR, and bZIP61). This study provides a theoretical and experimental basis for poplar germplasm development with enhanced salt tolerance and improved carbon sequestration capacity.
Subtropical perennials lack formal winter dormancy mechanisms, rendering them more vulnerable to cold stress than temperate or boreal trees. While cold-response pathways are well characterized in model plants, the regulatory landscape in woody species remains elusive. Here, we demonstrate that shoot apices of the fast-growing subtropical tree Eucalyptus grandis respond to cold stress within 0.5 h through rapid chromatin accessibility remodeling and transcriptomic reprogramming. Time-series ATAC-seq and RNA-seq analyses revealed a hierarchical regulatory architecture over a 24 h period; this architecture is initiated by hormone- and circadian-related genes, followed by metabolic, cell-cycle, and physiological adjustments. Transcriptomic reprogramming was concentrated in cold- and red-light-responsive genes (e.g., CBF1 and CBF4), which were induced as early as 0.5-2 h post-treatment. Functional validation confirmed that four rapid cold-responsive motifs, including a CBF-binding site, exhibited elevated luciferase activity at 4 °C. While over 50% of dynamic chromatin accessibility regions correlated with differential gene expression, chromatin opening did not always coincide with immediate transcriptional activation. Notably, canonical auxin signaling components exhibited sustained induction and synchronized chromatin-expression dynamics. De novo motif analysis indicated that constitutively expressed AGL42 and ERF transcription factors in shoot apices may directly activate CBF4, initiating a 'development-to-stress' switch via downstream chromatin remodeling. Direct activation of the CBF4 promoter by two Eucalyptus grandis AGL42 orthologs was confirmed, establishing a novel regulatory relationship in the cold response. These findings provide a high-resolution map of how chromatin accessibility integrates transcription factors into a hierarchical regulatory network to modulate cold adaptation in subtropical woody plants.
The shoot apical meristem of vascular plants generates all the aboveground organs. During this process, the structure and function of the meristem are maintained by a group of regulatory genes, among which the WUSCHEL (WUS)-CLAVATA3 (CLV3) module plays the core role. To date, all of the insights into shoot meristem homeostasis have been derived from studies on herbaceous plants. The mechanism by which the shoot meristem is maintained in trees remains unknown. In this study, we analyzed the functions of the poplar genes PagWUS and PagCLV3, homologs of Arabidopsis WUS and CLV3, respectively, in the maintenance and regeneration of the shoot meristem. Our results reveal both conserved and divergent functions compared to those of their orthologs in herbaceous species. Similar to their herbaceous counterparts, PagWUS and PagCLV3 are specifically expressed in the organizing center and stem cells, respectively, and form a feedback loop that regulates shoot meristem maintenance. Overexpression of PagWUS promoted shoot regeneration. Compared with herbaceous species, poplar possesses a much larger stem cell niche. The function of the PagWUS-PagCLV3 module is consistent with the developmental characteristics of perennial trees in that it regulates the cessation of the shoot meristem and mediates the proper pattern of secondary growth. Disruption of PagCLV3 enhanced shoot regeneration capacity. Our results shed light on shoot meristem regulation in trees and pave the way for understanding the mechanisms of meristem activity and plant development.
Mulberry (Morus spp.) includes ecologically important tree species that are highly valued for their exceptional economic and medicinal properties. Among its diverse species, Morus wittiorum and Morus laevigata are particularly valuable genetic resources because of their resistance to Sclerotinia, their relatively high content of specific flavonoids, and elongated fruit morphology. In this study, hybridization experiments were conducted using 10 mulberry accessions spanning three taxonomic sections (Alba, Wittiorum, and Laevigata). All six attempted intersectional crosses successfully yielded hybrid progeny. Using genomic in situ hybridization with blocking DNA, we detected distinct chromosomal signal patterns among the three sections, enabling precise identification of hybrid and wild-type chromosomal constitutions. Notably, this study provides the first documented evidence of 2n gamete formation in the genus Morus, where 2n eggs from M. wittiorum 'W-4' produced a pentaploid hybrid, 'Mp-7'. This discovery not only rewrites the chromosomal inheritance patterns of Morus but also unveils untapped polyploid breeding potential. These findings provide an efficient approach for identifying hybrids and offer novel polyploid breeding strategies, thereby promising to reshape global mulberry breeding and creating new opportunities for the genetic improvement of this agronomically important species.
Major latex-like proteins (MLPs) play crucial regulatory roles in mediating plant responses to both abiotic and biotic stressors. Although MLPs have been identified in diverse plants, the genome-wide characteristics of MLP-encoding genes and their roles in pathogen defense in Paulownia (Paulownia fortunei) remain largely unexplored. P. fortunei is a fast-growing perennial tree widely cultivated across multiple regions of Asia due to its substantial economic and ecological value. Here, we identified 49 PfMLP genes from the P. fortunei genome and systematically characterized their sequence architectures and phylogenetic relationships. Transcriptome analyses revealed 16 PfMLPs that are responsive to Witches' Broom (PaWB) phytoplasma infection. Notably, we focused on the functional characterization of PfMLP25, whose expression was induced by PaWB infection. Heterogenous overexpression of PfMLP25 in transgenic poplars enhanced pathogen resistance, confirming its critical role in anti-pathogen defense. Additionally, we demonstrated that the PfMYB100 transcription factor regulates the transcription of PfMLP25 and identified its interaction with two key immune system-essential proteins, PfCDPKa and PfRODa. Furthermore, we validated the interaction between PfMLP25 and the PfPUBa protein, indicating a potential role for PfMLP25 in the ubiquitination pathway during PaWB phytoplasma invasion. Taken together, our findings suggest that PfMLP25 functions by mediating immune system activation and participating in ubiquitination processes during PaWB phytoplasma invasion. This study presents new insights into the role of PfMLP25 and its underlying molecular mechanisms in plant pathogen defense.
Flavonoids are the primary bioactive compounds in Ginkgo biloba leaves. However, the regulatory mechanisms underlying their biosynthesis remain incompletely understood. In this study, three G. biloba exhibiting significant differences in flavonoid content were selected from a total of 26 cultivars. Integrated metabolomic, lncRNA, and mRNA sequencing analyses identified GbCHS as a core gene involved in flavonoid biosynthesis. Overexpression of GbCHS markedly enhanced flavonoid accumulation, whereas virus-induced gene silencing (VIGS) of GbCHS resulted in a significant reduction in total flavonoid content, confirming its essential role in flavonoid biosynthesis. Notably, GbCHS-silenced G. biloba plants also exhibited a significant decrease in plant height, leaf weight, root length, and lateral root number. In contrast, Arabidopsis thaliana plants overexpressing GbCHS showed significant increases in plant height, leaf weight, root length, and lateral root number, indicating that this gene also promotes plant development. Furthermore, GbCHS was found to be partially complementary to the lncRNA LncNAT1.Overexpression of LncNAT1 in G. biloba calli significantly suppressed GbCHS expression and reduced total flavonoid content, whereas silencing LncNAT1 led to increased GbCHS expression, flavonoid accumulation, plant height, and leaf weight. Mechanistically, LncNAT1 represses GbCHS expression through the formation of an LncNAT1-GbCHS RNA duplex. Collectively, these findings reveal the multidimensional regulatory functions of the novel LncNAT1-GbCHS module in flavonoid biosynthesis and plant development in G. biloba.
