Search Results (659)

The Sugars Will Eventually be Exported Transporters (SWEET) family plays a crucial role in the carbohydrate distribution, phloem loading, and stress response of plants, yet the evolutionary characteristics and functional diversification of SWEET genes in the endangered timber species Phoebe bournei (Hemsl.) Yen C. Yang remain largely unexplored. In this study, 21 PbSWEET genes were identified and classified into four subfamilies (A–D). Subfamily A exhibited a unique lineage expansion, mainly driven by tandem and segmental duplications. The nonsynonymous-to-synonymous substitution ratio (Ka/Ks) values of all duplicate gene pairs were all less than 1, indicating a strong selective suppression effect; consistent with this evolutionary constraint, the majority of PbSWEET proteins harbor the conserved Medicago truncatula Nodulin 3/saliva (MtN3_slv) domain, with only a few exceptions lacking a complete version. Promoter and hormone response analyses revealed that under abscisic acid (ABA) stress, PbSWEET4 exhibited an immediate burst, whereas PbSWEET10 showed a delayed burst. Physiological data indicated that soluble sugars may be more dominant osmolytes than proline (Pro), a pattern that points to a potential carbon-centric regulatory strategy. PbSWEET4 showed an early burst before sugar/oxidative peaks, suggesting a possible non-canonical signaling role, whereas PbSWEET10 exhibited a late increase coinciding with sugar/malondialdehyde (MDA) peaks, suggesting potential involvement in sugar redistribution. Under methyl jasmonate (MeJA) treatment, PbSWEET10 was rapidly induced, yet sugar accumulation occurred only at 24 h, a temporal decoupling that suggests a possible transcription–metabolism decoupling. Collectively, these correlative patterns point to a possible dual-wave transcriptional mechanism and nominate PbSWEET10 as a candidate for stress response, though these inferences require functional validation. Full article

Phytoplasmas are a group of wall-less, unculturable prokaryotic pathogenic bacteria that colonize the phloem of plants and are transmitted by piercing–sucking insects. As a typical tropical island province in China, Hainan Island has abundant biodiversity due to its unique geographical location and climatic conditions, which provide a favorable ecological environment for the survival and propagation of phytoplasmas, which infect different hosts, cause different symptoms, or belong to different subgroups. Based on host species, disease symptoms and 16Sr subgroups, 69 representative phytoplasma records from four 16Sr groups have been identified on Hainan Island, showing rich diversity in host range and pathogen species. The diversity of plant hosts and the evolutionary relationship of phytoplasmas not only affect the occurrence and prevalence of phytoplasma-related diseases but also bring great challenges to the epidemic monitoring, detection, diagnosis and prevention management of these diseases. This review summarizes current research progress on host diversity, phylogenetic evolution, mixed infection, diversity of transmission vectors, and geographical isolation differentiation, as well as adaptive evolution of phytoplasmas on Hainan Island. Furthermore, the challenges brought by plant host diversity and phylogenetic evolution to disease monitoring, diagnosis and prevention management are discussed. This review aims to provide a comprehensive theoretical basis for the in-depth study of phytoplasma-related diseases on Hainan Island, and to offer practical guidance for scientific monitoring, early warning and comprehensive prevention and control of these diseases. Full article

Phytoplasmas are obligate intracellular plant pathogens that cause numerous severe plant diseases in agricultural crops worldwide. Phytoplasmas are transmitted primarily by phloem-feeding insect vectors such as leafhoppers, planthoppers, and psyllids, transmitting the pathogen between infected and healthy plants. Conventional management strategies mainly consider chemical insecticides, which often lead to environmental concerns, insect resistance, and limited long-term effectiveness. Consequently, innovative and sustainable approaches have emerged for managing phytoplasma vector populations and interrupting disease transmission only in the last few years. Several disease outbreaks, i.e., the expansion of the American grapevine leafhopper (Scaphoideus titanus) in Europe, underlined the necessity of developing new and innovative technologies for phytoplasma control. This article reviews classical and innovative pest management strategies against insect vectors of phytoplasma, and a detailed comparison of the efficiencies between methods is presented. The integration of these advanced approaches within integrated pest management (IPM) frameworks offers promising prospects for sustainable crop protection and phytoplasma disease mitigation. Full article

The red turpentine beetle, Dendroctonus valens LeConte, is an important phloem-feeding pest of pine forests in China. RNA interference (RNAi) is a conserved, sequence-specific gene-silencing mechanism induced by double-stranded RNA (dsRNA), and has become an important molecular tool for screening and evaluating potential targets for pest management owing to its high efficiency, target specificity, and relative environmental safety. In this study, six candidate genes were selected, including mesh and ssk responsible for gut barrier formation, actin involved in cellular structure maintenance, iap involved in apoptosis regulation, hsp70-2 responsible for stress response, and v-atpaseE involved in ion transport and cellular homeostasis. The effects of dsRNA microinjection on gene silencing and mortality were then evaluated in both larvae and adults of D. valens. Following dsRNA treatment, all six candidate genes were significantly downregulated in both larvae and adults, with v-atpaseE showing the strongest transcript suppression in larvae. Survival analysis revealed target-dependent lethal effects: v-atpaseE caused rapid larval mortality, reaching 100% by day 3, whereas ssk caused the strongest adult mortality, reaching 100% by day 5, and mesh also induced substantial adult mortality. In contrast, actin, iap, and hsp70-2 produced weaker or slower lethal effects. These results indicate that dsRNA injection can induce effective gene silencing in D. valens and that the resulting phenotypic responses differ among target genes and between life stages. Taken together, v-atpaseE and ssk represent the most promising candidate targets for further development of RNAi-based management strategies against D. valens. Full article

Background: Grapevine leafroll-associated virus 3 (GLRaV-3) is a severe phloem-limited grapevine virus, meaning it is restricted to sugar-transporting vascular tissue, which helps explain its strong effects on leaf physiology and carbon transport. However, its impact on leaf oxidative status, phenolic composition, and volatile organic compounds (VOCs) remains insufficiently characterized. Methods: Virus-free and GLRaV-3-infected grapevine leaves were analyzed for photosynthetic pigments, oxidative stress markers, phenolic compounds, and VOCs using spectrophotometric assays, HPLC-DAD/FLD, and SPME-Arrow-GC/MS. Data were evaluated using one-way ANOVA, multiple testing correction, principal component analysis (PCA), and exploratory partial least squares-discriminant analysis (PLS-DA). Results: GLRaV-3-infected leaves showed lower chlorophyll a (576.75 vs. 657.85 mg 100 g⁻¹ DW), chlorophyll b (282.96 vs. 314.05 mg 100 g⁻¹ DW), and total carotenoids (125.89 vs. 154.65 mg 100 g⁻¹ DW), but higher malondialdehyde (11.91 vs. 8.73 nmol g⁻¹ DW), H₂O₂ (0.36 vs. 0.25 μmol g⁻¹ DW), and proline (8.83 vs. 7.98 μmol g⁻¹ DW). Phenolic profiling showed increased levels of several flavonols and hydroxycinnamic acids, including kaempferol-3-O-glucuronide (2.81-fold), myricetin-3-O-glucoside (1.75-fold), quercetin-3-O-glucuronide (1.48-fold), and caffeic acid (1.30-fold). VOC profiling revealed higher relative abundances of several green leaf volatile-related compounds and methyl salicylate, including 1-methoxy-2-propanol (1.85-fold), 1-penten-3-ol (1.58-fold), hexanal (1.42-fold), and methyl salicylate (1.37-fold). PCA summarized treatment-related differences, with the first two components explaining 63.73% of phenolic and 74.09% of VOC variability, while exploratory PLS-DA/VIP analysis further supported the identification of treatment-associated discriminant metabolic features. Conclusions: GLRaV-3 infection is associated with reduced pigment content, increased oxidative stress markers, and coordinated changes in phenolic and VOC profiles. These metabolite changes provide insight into grapevine responses to viral infection and highlight GLRaV-3-associated metabolic features for future targeted studies of grapevine leafroll disease. Full article

Sugar beet cultivation in Europe is threatened by two vector-borne diseases: syndrome “basses richesses”, caused by the phloem-limited pathogen ‘Candidatus Arsenophonus phytopathogenicus’, and phytoplasmoses associated with ‘Ca. Phytoplasma solani’ subgroup 16SrXII-A and the related subgroup 16SrXII-P. Infections lead to reduced sugar yield, biomass and growth abnormalities. In Germany, Pentastiridius leporinus represents the main vector. Despite their importance, genetic diversity remains poorly understood. During a two-year survey, barcoded amplicons were generated from infected sugar beet samples from Germany and neighbouring countries using the phytoplasma markers 16S rRNA-ITS-23S rRNA, tuf, and groEL-stamp-nadE, as well as rplO-secY-rpmJ and groEL for ‘Ca. A. phytopathogenicus’. Amplicon pools underwent single-molecule real-time sequencing and amplicon-sequence-variant inference. Additionally, planthopper samples from sugar beet in Germany were analysed and compared to sugar beet data for ‘Ca. A. phytopathogenicus’. No genetic diversity of ‘Ca. A. phytopathogenicus’ was detected, whereas 16SrXII-A and -P showed variation below the subgroup level. 16SrXII-A exhibited higher diversity than 16SrXII-P. In Germany, 16SrXII-A formed a single cluster, while 16SrXII-P comprised two clusters based on 16S rRNA-ITS-23S rRNA. In neighbouring countries, only 16SrXII-A showed diversity, resolving up to four clusters by groEL-stamp-nadE. These results provide a basis for the identification of dominant strains supporting comparative variety evaluation for tolerance. Full article

Dendroctonus valens LeConte represents a major invasive pest species in China. Both larvae and adults primarily feed on the phloem of the tree trunk base and roots, disrupting nutrient transport and leading to host tree mortality, which poses a severe threat to forest ecosystems and the forestry economy. Juvenile hormone acid methyltransferase (JHAMT) is a key enzyme in insect juvenile hormone (JH) biosynthesis. In this study, we identified a JHAMT-encoding gene, DvJHAMT, in D. valens via bioinformatic analysis. RT-qPCR analysis revealed that DvJHAMT is predominantly expressed during the egg and larval stages. In the fourth-instar larvae, the highest expression levels were observed in the head and epidermis, suggesting a central regulatory role during this critical developmental period. To investigate its function via RNA interference (RNAi), a nanomaterial, star polycation (SPc), was employed for the transdermal delivery of dsRNA into the fourth-instar larvae. The results demonstrated that DvJHAMT knockdown significantly downregulated mRNA levels, resulting in marked decreases in larval survival, pupation, and eclosion rates. Notably, treatment with 0.7 µg dsDvJHAMT-SPc resulted in a 96.67% mortality rate and a reduced pupation rate of 41.67% at 34 days post-treatment. Furthermore, RNAi led to developmental deformities and significant weight loss in larvae. ELISA assays confirmed that DvJHAMT silencing led to reduced JHAMT enzyme activity and JH III titers in a dose-dependent manner. In conclusion, our findings demonstrate that DvJHAMT plays a vital role in JH biosynthesis and that its suppression exhibits potent lethal effects, suggesting that DvJHAMT is a promising candidate for RNAi-based management of D. valens. Full article

Huanglongbing (HLB), primarily caused by ‘Candidatus Liberibacter asiaticus’ (CLas), threatens global citrus production. Deciphering the molecular interplay between citrus and CLas is crucial for successful control. This review synthesizes current understanding of the molecular mechanisms underlying citrus-CLas interactions, providing a comprehensive overview that spans immune signaling, hormonal and metabolic reprogramming, non-coding RNA-mediated regulation, pathogen effector biology, and emerging biotechnological interventions. We detail the hierarchical host response: initial immune recognition via pattern recognition receptors, triggering reactive oxygen species bursts and calcium signaling. Moreover, hormonal network reprogramming and their complex interplay in defense/susceptibility are examined. Transcriptomic studies have revealed key features of metabolic reprogramming, including suppression of photosynthesis and impairment of phloem function. Additionally, long-term strategies like cell wall reinforcement, accumulation of defensive compounds such as flavonoids and terpenoids, and roles of post-transcriptional regulation of microRNAs are discussed. Conversely, CLas counter-defense, notably effector-mediated immunity suppression and host metabolism manipulation, is also considered. Comparative transcriptomics between tolerant and susceptible varieties identifies tolerance or resistance genes/pathways for breeding and engineering. Despite this progress, critical knowledge gaps remain, particularly regarding the precise molecular mechanisms of CLas immune evasion and effector-mediated suppression, the genetic basis of natural tolerance, and the field-level efficacy of defense priming strategies. Future research directions should integrate single-cell omics, CRISPR/Cas9 editing, nano-enabled delivery, and microbiome engineering to bridge these gaps and accelerate HLB-tolerant/resistant citrus development. This review synthesizes how molecular profiling advances understanding of citrus defense mechanisms against HLB, and underscores the imperative for interdisciplinary research and global collaboration. Full article

The grain aphid, Sitobion miscanthi, poses a serious threat to cereal crops worldwide, leading to considerable yield losses and demanding annual insecticide applications during the grain-filling stage. As a sustainable alternative, we explored host-induced gene silencing (HIGS) targeting an aphid-specific gene. In this study, we identified SmDSR32, a novel gene encoding a salivary peptide in S. miscanthi, and validated its suitability for RNAi. Transgenic wheat lines expressing SmDSR32-dsRNA were generated. Aphids feeding on these lines showed a 20-fold reduction in SmDSR32 transcript levels compared with controls. This silencing disrupted normal feeding behavior in electropenetrography (EPG) analyses, characterized by a 1.94-fold prolongation of intercellular probing and a 61% shortening of phloem ingestion. Consequently, aphid performance was severely compromised, with at least a 56.7% decrease in survival, a shortening of 5 days in lifespan, and a reduction of 9–10 individuals in aphid progeny production. Impressively, upon being transferred to wild-type plants, both the surviving aphids and their progeny sustained fitness deficits, with a 30% reduction in survival still observed in the first generation. These findings validate SmDSR32 as a potent RNAi target and establish HIGS targeting essential salivary genes as a promising strategy for sustainable aphid management in wheat. Full article

Inflammatory bowel disease (IBD) involves intestinal barrier dysfunction and chronic inflammation. Manna, derived from the solidified phloem sap of Fraxinus species, is rich in mannitol and polyphenols and valued for its laxative, antioxidant, and anti-inflammatory properties. In this study, manna was digested in vitro to obtain its bioaccessible fraction (BFM), whose anti-inflammatory activity was tested in a Caco-2/RAW264.7 co-culture model. Caco-2 cells were pretreated with BFM (1/20 v/v, 6 mg/mL) 90 min before LPS stimulation (1 µg/mL, 24 h) of macrophages, using budesonide (1 μM) as reference. BFM pretreatment significantly reduced IL-8 secretion (70.8%) in Caco-2 cells, and IL-6 (43.1%) and TNF-α (83.1%) in RAW264.7 macrophages. It also improved redox balance in Caco-2 cells by decreasing iNOS (48.2%), NOx (33.2%), and ROS (26.4%), while stabilizing tight junctions through occludin upregulation (18.3%). Mechanistically, BFM downregulated NF-κB-COX-2-PGE₂ signaling in macrophages, reducing NF-κB p65 nuclear translocation (65.6%), COX-2 levels (79.3%), and PGE₂ production (50.8%). Co-treatment with budesonide showed antagonism for most markers (Combination Index (CI), 0.41–0.76), but additive/synergistic effects on ROS (CI, 1.06 ± 0.06) and NOx (CI, 1.10 ± 0.04). These findings highlight manna’s strong anti-inflammatory activity at a low, non-laxative dose (3.8 g/day), supporting its nutraceutical potential in IBD management. Full article

Knot-free timber production in Cunninghamia lanceolata depends critically on internodal characteristics, yet the mechanisms governing internode elongation remain poorly understood, hindering breeding efforts for longer-internode varieties. In this study, we selected two clones with distinct internodal traits (the C1 clone exhibited a 25.03% longer internodal length than the C11 clone) as materials. Enzyme-linked immunosorbent assay (ELISA) and RNA sequencing were used to investigate dynamics in endogenous hormones and transcriptional regulation in internodal growth. Results showed that the difference in indole-3-acetic acid (IAA) rhythms in apical buds is a key factor of C1’s longer internodal growth; higher levels of IAA and cytokinins in the apical buds of C1 may support sustained internodal growth; upregulated IAA-related genes in upper phloem (PIN1 and SAURs), which are involved in polar transport and signal response, indicates a stronger capacity to establish apical dominance. Hormone transport may be regulated by very long-chain fatty acids (VLCFAs). Consistent with reduced brassinosteroid activity, genes involved in VLCFA biosynthesis and transport were generally lower in C1, implying excessive VLCFA accumulation in C11 may be negative to IAA transporting and internode growth. This study offers a preliminary insight into internodal growth mechanisms influenced by hormone biosynthesis and transport in C. lanceolata., providing a basis for genetic improvement, germplasm selection, and exogenous hormone applications in knot-free timber cultivation. Full article

Papaya (Carica papaya L.) is a widely cultivated tropical and subtropical fruit crop valued for its rich nutritional content, diverse food industry applications, and the medicinal use of papain. However, bitterness in papaya fruit, particularly in fibrous strands, negatively affects fruit quality and consumer acceptance; therefore, the development of papaya cultivars with stable and desirable quality is of great importance. To identify the bitter compounds in papaya fruit fibrous strands and elucidate the molecular mechanisms underlying their biosynthesis, we performed transcriptomic and metabolomic analyses of fibrous strands from two papaya cultivars at three developmental stages. We identified carpaine, dehydrocarpaine II, and their derivative alkaloids. Furthermore, we identified two key regulatory genes, CpNAC82 and CpHD-Zip ANT2, associated with alkaloid biosynthesis. Finally, using single-nucleus RNA sequencing technology, we constructed a comprehensive gene expression atlas of papaya fibrous strands and stems, successfully identifying multiple cell types, including epidermal cells, guard cells, parenchyma cells, and phloem cells. Epidermal and phloem cells serve as the primary sites of alkaloid metabolism in papaya. These findings provide new insights into the molecular mechanisms of bitterness in papaya’s fibrous strands and yield genomic resources for improving fruit quality in papaya. Full article

Temperature is a major determinant of plant metabolic plasticity, yet its role in directing volatile and semi-volatile specialized metabolism in Ginkgo biloba remains poorly understood. In this study, we investigated how contrasting low- and high-temperature treatments reshape secondary metabolite contents in G. biloba microclones cultivated in vitro. Plants were exposed to cold (+3 °C) and heat (+30 °C) conditions, and their responses were analyzed using GC–MS profiling, anatomical measurements, chlorophyll fluorescence, and multivariate statistics. Cold treatment selectively increased the abundances of monoterpenes (13.22%) and sesquiterpenes (13.83%), with the strongest accumulation of caryophyllene, eucalyptol, and (1S)-camphor. In contrast, heat treatment reduced ester content to 3.73% and strongly enriched oxy-sesquiterpenes (46.50%) and lactone/ketone/spiroketone (29.54%) contents. The enhanced accumulation of isocalamendiol, isoshyobunone, cyclohexanone derivative, dehydroxy-isocalamendiol, and (+)-2-bornanone was observed under heat. According to the multivariate analysis, control plants were associated with traits reflecting optimal physiological performance, including greater parenchyma, phloem, and xylem thickness, larger vascular bundles, longer stomata, and higher NPQ, qN, Y(NPQ), and F_v/F_m. Cold-treated plants showed thicker epidermis and sclerenchyma, higher stomatal density and width, elevated Y(NO), and an enrichment of esters and terpenoids, whereas heat-treated plants were characterized by thicker adaxial and abaxial epidermis, increased mesophyll thickness, and higher levels of oxygenated metabolites. These findings expand current knowledge beyond terpene trilactones and flavonoids and identify Ginkgo microclones as a useful in vitro model for temperature-guided metabolic reprogramming and targeted metabolite enrichment. Full article

Manganese (Mn) is an essential micronutrient required for plant growth, photosynthesis and metabolic regulation. Its importance is related to the involvement in several metabolic processes that ensure proper cellular function and balanced plant development throughout the production cycle. In plants, Mn is absorbed predominantly as Mn²⁺, and its availability is strongly influenced by soil pH, aeration, and other mineral nutrients in the soil solution. After uptake by roots, Mn is translocated to the shoot, accumulating primarily in metabolically active organs such as stems, young leaves and flowers. Although Mn exhibits limited mobility in the phloem, adequate concentrations are necessary to sustain both vegetative development and reproductive growth. Adequate Mn concentration is directly reflected in fruit development, as well-nourished plants show improved flowering, greater assimilate translocation capacity, and better fruit filling, thereby positively influencing yield and quality. However, Mn deficiency is common in alkaline soils or soils with high organic matter, causing interveinal chlorosis in young leaves, reduced growth, and lower biomass production. Under prolonged conditions, deficiency leads to less vigorous plants with reduced metabolic efficiency. Conversely, Mn toxicity, typically associated with acidic and poorly drained soils, restricts root development and induces nutritional imbalances with other elements, such as calcium, magnesium, and iron. Therefore, proper Mn management is essential to ensure nutritional balance and optimal performance of agricultural crops. Overall, this review synthesizes advances in Mn transport, cellular compartmentalization, and metabolic regulation, emphasizing how Mn interacts with other mineral nutrients to influence plant physiology. Attention is given to the integration of Mn with redox networks, photosynthetic regulation, and reproductive development. By linking transport mechanisms with physiological outcomes, this review identifies key patterns governing Mn homeostasis and highlights implications for crop nutrition and sustainable nutrient management. Full article

Low-temperature stress during the jointing stage severely disrupts the coordination of the source–flow–sink system in winter wheat. To elucidate the underlying mechanism, three wheat cultivars with different winter habits (Zhenmai 12, Jimai 22, and Shannong 38) were selected and subjected to six temperature levels (−6 °C to 8 °C) and three stress durations (2–6 days). The effects of vascular bundle traits on the transport of photosynthetic products, dry matter distribution, and yield formation were analyzed. The results showed that Zhenmai 12 and Jimai 22 completely ceased photosynthesis under 0 °C and −3 °C, respectively. The leaf vascular bundle area continuously decreased with increasing low-temperature stress, while the proportion of xylem and phloem initially increased by approximately 15% and 10%, respectively, before rapidly decreasing to 65% of the control value. In the stem, the three vascular bundle parameters initially increased by 20%, 25%, and 20%, respectively, before quickly decreasing to 50%. Changes in the vascular bundle structure weakened the transport capacity of assimilates, with dry matter in leaves and stems decreasing by 15–20% and 10%, respectively, while the root dry matter increased by 20–30%. Correlation analysis revealed highly significant relationships (p < 0.001) between vascular bundle parameters and yield components. Principal component and cluster analyses indicate that the area of leaf and stem vascular bundles, maximum net photosynthetic rate, and water use efficiency may be key indicators in explaining the variation in yield. Radar plots further validated this finding, showing that Zhenmai 12 and Jimai 22 are more sensitive to changes in the maximum net photosynthetic rate, while Shannong 38 exhibits a greater sensitivity to changes in water use efficiency. Based on existing research on photosynthetic pathways and dry matter distribution, this study innovatively investigates the potential relationship between material transport and yield formation under low-temperature stress during the jointing stage from the perspective of anatomical structure and functional coupling. The findings provide new insights into understanding the structural impact of low-temperature stress on crop yield formation and offer theoretical support for identifying the structural basis of limited material transport under stress and for developing disaster diagnostic models driven by structural parameters. Full article