Tomato leaf mold, caused by Cladosporium fulvum, is a destructive foliar disease in protected cultivation. Biological control using Trichoderma and plant defense elicitors such as melatonin offers a sustainable alternative to chemical fungicides. However, the synergistic effect of combining Trichoderma with melatonin and the role of endogenous melatonin in Trichoderma-induced resistance to tomato leaf mold remain unclear. In this study, we screened ten Trichoderma strains and identified T. asperellum T141 strain as the most effective antagonist against C. fulvum in dual culture assays. Moreover, exogenous melatonin (100 μmol/L) resulted in the lowest disease index and significantly reduced malondialdehyde content. The combined application of T. asperellum and melatonin prior to pathogen inoculation reduced the disease index by 77.57% and promoted plant growth compared with pathogen-only controls. The combination also decreased H2O2 and O2·-, elevated antioxidant enzyme (SOD, POD, CAT, and APX) activities, and restored photosynthetic parameters, pigment contents, Rubisco activity, FBPase activity, and expression of photosynthesis-related genes (FBPase, SBPase, FBPA, and TPI). Virus-induced gene silencing of the COMT1 gene, a key melatonin biosynthesis gene, drastically reduced endogenous melatonin, and largely compromised T. asperellum-induced resistance, along with attenuated antioxidant defense and photosynthetic recovery. Collectively, our results demonstrate that T. asperellum and melatonin synergistically protect tomato against C. fulvum by mitigating oxidative stress and preserving photosynthetic function, and that COMT1-dependent endogenous melatonin synthesis is essential for T. asperellum-induced resistance. This study provides a theoretical basis for developing Trichoderma-melatonin biopreparations as an eco-friendly strategy for the management of tomato leaf mold.

Salinity stress has been proved to have detrimental effects to plant growth and development. This experiment investigated the effects of alanine (AL, 2 mM) and sorbitol (SB, 1.5%) on soybean growth in salt-affected soil. Four treatments were set: control, AL, SB, AL+SB. Results demonstrated that both AL and SB had positive effects, especially the combined application of AL+SB exhibited largest mitigation effects to salt stress. Under this treatment, the plant height (54.79%), stem dry weight (22.62%), leaf dry weight (30.54%) and root dry weight (20.08%) increased significantly compared to the control. In addition, the contents of chlorophyll a, chlorophyll b, and total chlorophyll were enhanced by 17.00%, 100.00%, and 45.60%, respectively, while the electrolyte leakage reduced by 23.06%, suggesting improved membrane stability. Furthermore, the treatment promoted the accumulation of K+ and Ca2+ in leaves and stems. SOD, POD, CAT and APX activities were significantly reduced in this treatment, suggesting a lower oxidative burden. The findings underline that application of 2 mM alanine and 1.5% sorbitol as well as their combination is a potential integrated strategy for enhancing soybean growth, photosynthesis, and stress resilience in saline soils.

To explore the heat tolerance capabilities of 10 ground cover plant species, treatments using maximum temperatures of 25 degrees C (control), 30 degrees C, 35 degrees C, and 40 degrees C were performed in growth chambers. Compared with the control group (25 degrees C), under heat stress (30 degrees C, 35 degrees C, and 40 degrees C), the largest reductions in root activity and transpiration rates occurred in M. cordifolium (86.04%) and D. chinensis (61.77%), respectively. Except for P. lanceolata, V. hybrida, and D. chinensis, the reduction in water content for the other seven species (including C. roseus) was less than 5%. Under 40 degrees C stress, photosynthesis-related indicators such as relative chlorophyll content, net photosynthetic rate, and stomatal conductance decreased by 1.39%-67.29%, 7.75%-52.46%, and 1.09%-57.28% respectively, while intercellular CO2 concentration increased by 12.08%-40.40% when compared to the control in the ten plant species. Under different temperature treatment conditions, superoxide dismutase (SOD) and peroxidase (POD) activities were highest in C. roseus, reaching 250.39 U/(gmin) and 3017.59 U/(gmin), respectively, while catalase (CAT) activity was highest in P. lanceolata at 152.73 U/(gmin). Malondialdehyde (MDA) content rose after increasing temperatures from 25 degrees C to 35 degrees C. However, the change trends of soluble protein, soluble sugar, and proline contents varied, ranging from -57.17% to 48.56%, -53.22% to 501.02%, and -47.66% to 227.34%, respectively. Principal component analysis showed that the first five principal components had a cumulative contribution rate of 83.162%. The membership function method combined with cluster analysis results allowed for the classification of these plants into three categories: strong heat tolerance (C. roseus, P. lanceolata, and T. fournieri, three species in total), moderate heat tolerance (V. hybrida, A. hispida, M. cordifolium, P. 'Cerveza'n Lime', and C. scutellarioides, five species in total), and weak heat tolerance (D. chinensis and T. cerinthoides 'Nanouk', two species in total). In summary, this study provides a physiological basis for selecting ground cover plant resources that could be used in areas with different temperatures

Toxic heavy metal chromium (Cr) poses significant risks to crop yields and human health through contamination of the food chain. Dopamine, a naturally occurring bioactive amine, can enhance plant tolerance to various abiotic stresses; however, its specific role in Cr stress tolerance and the associated molecular mechanisms remain largely unexplored. In this study, we demonstrate that root application of dopamine effectively mitigates Cr stress in tomato plants. Cr stress was found to decrease chlorophyll content, maximum photochemical efficiency, shoot growth, and biomass accumulation, while simultaneously increasing reactive oxygen species (ROS) accumulation, lipid peroxidation, and electrolyte leakage. Exogenous dopamine application significantly reduced excessive ROS accumulation and malondialdehyde levels, thereby alleviating oxidative stress. This was achieved through the enhancement of antioxidant enzyme activity, increased glutathione and phytochelatin contents, and the upregulation of the expression of respective encoding genes, including Cu-Zn SOD, POD, CAT1, APX, GR1, GSH2, and PCS. Additionally, dopamine treatment induced the expression of RBOH1 and reduced Cr content. Notably, exogenous H2O2 application also improved Cr tolerance, but the application of diphenyleneiodonium, an NADPH oxidase inhibitor, exacerbated Cr phytotoxicity and diminished the beneficial effects of dopamine on plant tolerance to Cr stress. These findings suggest that dopamine-induced H2O2 signaling plays a crucial role in enhancing Cr tolerance. This study elucidates a fundamental mechanism underlying dopamine-mediated Cr tolerance and expands our understanding of the stress resistance properties of dopamine in plants.

Root-knot nematode (RKN) infestation is a major threat to global agriculture, causing substantial damage to economically important crops such as tomatoes. Trichoderma species are promising biocontrol agents that can enhance plant growth, improve nutrient uptake, and induce systemic resistance against various pathogens, including RKNs. The R2R3-MYB transcription factor family plays a key role in plant secondary metabolism and defense mechanisms against biotic stressors. However, the specific role of tomato MYB108 in mediating resistance against RKNs remains underexplored. In this study, we found that RKN infestation decreases MYB108 expression, whereas Trichoderma harzianum inoculation significantly enhances MYB108 expression. Silencing MYB108 expression in tomato plants using the virus-induced gene silencing (VIGS) technique enhances susceptibility to RKNs as evidenced by a marked increase in gall number and root galling index (increased by 16.53 % and 16.10 %, respectively), alongside a reduction in the biocontrol efficacy of Trichoderma (decreased by 29 %). Furthermore, MYB108 silencing exacerbates RKN-induced oxidative stress, as evinced by elevated levels of hydrogen peroxide, superoxide anion, malondialdehyde, and electrolyte leakage. MYB108 silencing also attenuates the accumulation of key secondary metabolites such as flavonoids, phenols, and lignins, and reduces the activities of enzymes and the expression of genes associated with secondary metabolite synthesis. Although Trichoderma inoculation mitigates RKN-induced oxidative stress and enhances secondary metabolite synthesis, the silencing of MYB108 refutes the beneficial effects of Trichoderma on both secondary metabolite production and antioxidant capacity. Analysis of the transcriptional start site located 2000 base pairs upstream of the promoter regions of PAL, C4H, 4CL, and DFR reveals multiple MYB binding sites, indicating that MYB108 potentially plays a significant role in the transcriptional regulation of secondary metabolism. En masse, these findings highlight the critical role of MYB108 in mediating Trichoderma-induced resistance to RKNs and emphasize its potential as a target for enhancing plant resilience to RKNs.

As low temperature is a key factor affecting the growth and development of plants and the utilization of agricultural waste has significant research value, this study explores the effects of 16 agricultural wastes on the growth of P. fraseri under natural low-temperature conditions and evaluates its cold resistance capacity. Soil chemical properties were analyzed and all the wastes were found to exhibit alkalinity. The highest total nitrogen content was found in group A (garden soil/coir/municipal sludge = 7:1:2). In this group, the branch number, branch length, and branch diameter were the largest. Interestingly, the plants in group E (garden soil/coir/pig manure = 7:1:2) had the highest average number of new shoots, with 5.72. Analysis of the physiological indexes of leaves revealed that the proline content, superoxide dismutase activity, fresh weight, and dry weight of plants in group L (garden soil/coir/pear residue = 7:1:2) were the highest. The stomatal conductance and transpiration rate of the leaves of plants in group L were the largest, at 86.23 mmol∙m−2∙s−1 and 1.67 mmol∙m−2∙s−1, respectively. Furthermore, combined with morphological and physiological indicators for membership function analysis, the results show that plants in group A exhibited optimal growth under natural low temperature. Correlation analysis indicated varying degrees of correlation between 38 pairs of indicators, including branch number and branch length, intercellular CO2 concentration and stomatal conductance, and leaf fresh weight and dry weight. Heatmap analysis showed that branch number, branch length, and branch diameter were highest in group A plants, while the highest levels of proline occurred in group L plants. In this study, groups A and L are recommended for growth under naturally low-temperature conditions.

Potassium-enriched biochar (KBC) serves as a novel soil amendment that improves soil fertility and enhances crop stress resistance. This study preliminarily investigated the regulatory effects of different KBC concentrations on soybean (Glycine max) seedling growth and the antioxidant system under salt stress through pot experiments. Under normal cultivation conditions, 1% KBC application significantly promoted seedling growth, increasing plant height and root length by 42.19% and 35.89%, respectively. Metabolic optimization was evidenced by reduced soluble sugar (35.33%) and proline (37.46%) levels at 1% and 2% KBC, respectively, indicating improved carbon-nitrogen metabolism. However, under Salt Stress (200 mmol/L NaCl), total phenolic and flavonoid contents were significantly decreased. The 2% KBC treatment comprehensively enhanced key antioxidant enzyme activities: Superoxide dismutase (SOD) showed the most pronounced increase (27.45%), while catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) showed coordinated upregulation. This synergistic enhancement effectively mitigated reactive oxygen species (ROS) accumulation. In conclusion, optimal KBC application (1-2%) simultaneously promotes soybean seedling growth, photosynthetic efficiency, and salt-stress tolerance through reinforced antioxidant capacity. These findings provide a theoretical foundation for saline soil remediation and stress-resistant soybean cultivation.

Biocontrol fungi may exert antagonistic effects by emitting volatile organic compounds (VOCs), thus identifying fungal VOCs is crucial for understanding biocontrol mechanisms and developing novel biofungicides. In this study, we examined the antagonistic effect of Irpex lacteus LL210 against three major fungal pathogens: Botrytis cinerea (tomato gray mold), Fusarium oxysporum (cucumber wilt), and Alternaria alternata (pepper leaf spots) using in vitro assays. The results of both the dual-culture and dual-petri-dish methods showed that I. lacteus LL210 strongly inhibited the growth of B. cinerea, likely through the release of volatile compounds. SPME-GC-MS analysis of I. lacteus LL210 identified 770 volatile compounds, of which 26 key volatiles were screened on the basis of their relative odor activity values, peak areas and concentrations. Further evaluation using the dual-petri-dish method showed that compounds such as 2-Octen-1-ol, (E)-; Benzeneacetaldehyde; (E)-2-Octenal; Hexanal; (E)-2-Butenal; 5-Heptenal, 2,6-dimethyl-; 1-Octanol; 2,3-dihydro-Benzofuran; Diallyl Sulfur compounds exhibited significant inhibition of B. cinerea, suggesting their potential utility in the development of novel fungicides. We also tested their effects on plant growth and physiology and found that 1-octanol had minimal deleterious effects on tomato plants, as evidenced by growth and oxidative stress markers. This study systematically deciphered the VOCs profile of I. lacteus LL210, revealing critical mechanisms of pathogen inhibition through both direct inhibitory effects of VOCs and plant-mediated enhanced defense. These findings have driven the development of potential biocontrol agents based on VOCs, thereby providing sustainable solutions for crop disease management.

Reactive oxygen species (ROS) are crucial signaling molecules in plants that play multifarious roles in prompt response to environmental stimuli. Despite the classical thoughts that ROS are toxic when accumulate in excess, recent advances in plant ROS signaling biology reveal that ROS participate in biotic and abiotic stress perception, signal integration, and stress-response network activation, hence contributing to plant defense and stress tolerance. ROS production, scavenging and transport are fine-tuned by plant hormones and stress-response signaling pathways. Crucially, the emerging plant hormone melatonin attenuates excessive ROS accumulation under stress, whereas ROS signaling mediates melatonin-induced plant developmental response and stress tolerance. In particular, RESPIRATORY BURST OXIDASE HOMOLOG (RBOH) proteins responsible for apoplastic ROS generation act downstream of melatonin to mediate stress response. In this review, we discuss promising developments in plant ROS signaling and how ROS might mediate melatonin-induced plant resilience to environmental stress.

Trichoderma spp. can enhance plant resistance against a wide range of biotic stressors. However, the fundamental mechanisms by which Trichoderma enhances plant resistance against Meloidogyne incognita, known as root-knot nematodes (RKNs), are still unclear. Here, we identified a strain of Trichoderma asperellum (T141) that could effectively suppress RKN infestation in tomato (Solanum lycopersicum L.). Nematode infestation led to an increase in the concentrations of reactive oxygen species (ROS) and malondialdehyde (MDA) in roots but pre-inoculation with T141 significantly decreased oxidative stress. The reduction in ROS and MDA was accompanied by an increase in the activity of antioxidant enzymes and the accumulation of flavonoids and phenols. Moreover, split root test-based analysis showed that T141 inoculation in local roots before RKN inoculation increased the concentration of phytohormone jasmonate (JA) and the transcripts of JA synthesis and signaling-related genes in distant roots. UPLC-MS/MS-based metabolomics analysis identified 1051 differentially accumulated metabolites (DAMs) across 4 pairwise comparisons in root division test, including 81 flavonoids. Notably, 180 DAMs were found in comparison between RKN and T141-RKN, whereas KEGG annotation and enrichment analysis showed that the secondary metabolic pathways, especially the flavonoid biosynthesis, played a key role in the T141-induced systemic resistance to RKNs. The role of up-regulated flavonoids in RKN mortality was further verified by in vitro experiments with the exogenous treatment of kaempferol, hesperidin and rutin on J2-stage RKNs. Our results revealed a critical mechanism by which T141 induced resistance of tomato plants against the RKNs by systemically promoting secondary metabolism in distant roots.

Anthocyanins, recognized as stress indicators, particularly under high-light conditions, play a pivotal role in plant stress responses. The advent of transcriptomics has opened avenues to elucidate the mechanisms underlying high light-induced anthocyanin biosynthesis. This study delved into transcriptomic changes in Begonia semperflorens leaves under varying light intensities: 950–9600 lx (TL_100), 6800–7000 lx (HS_75), and 4300–4500 lx (LS_25). To confirm the expression profiles of the key genes, we chose 12 critical genes associated with anthocyanin production for quantitative reverse transcription PCR (qRT-qPCR) analysis. Following this, we measured the levels of anthocyanins to substantiate the findings from the gene expression analysis. The transcriptome assembly in this study was extensive, yielding 43,038 unigenes that collectively spanned about 49.83 million base pairs, with an average unigene length of 1157 bp and an N50 value of 1685 bp. This assembly facilitated a thorough functional annotation across seven distinct protein databases, leading to the classification of 16,363 unigenes into 58 different families of transcription factors. Our comparative analysis of the transcriptomes highlighted a substantial number of differentially expressed genes (DEGs): 5411 DEGs between HS_75 and TL_100 conditions, with 3078 showing increased expression and 2333 showing decreased expression; 4701 DEGs between LS_25 and TL_100, consisting of 2648 up-regulated and 2053 down-regulated genes; and 6558 DEGs between LS_25 and HS_75, with 3032 genes up-regulated and 3526 down-regulated. These DEGs were significantly involved in critical pathways, such as anthocyanin synthesis, plant hormone signaling, and other regulatory mechanisms. This study suggests that genes, including F3′H, MYB102, and SWEET1, could play vital roles in regulating anthocyanin synthesis in response to various light conditions, potentially impacting the expression levels of other genes, like WRKYs, ATHB12, and those similar to HSP.

Trichoderma can enhance the metabolism of organophosphate pesticides in plants, but the mechanism is unclear. Here, we performed high-throughput transcriptome sequencing of roots upon Trichoderma asperellum (TM) inoculation and phoxim (P) application in tomato (Solanum lycopersicum L.). A total of 4059 differentially expressed genes (DEGs) were obtained, including 2110 up-regulated and 1949 down-regulated DEGs in P vs TM+P. COG and KOG analysis indicated that DEGs were mainly enriched in signal transduction mechanisms. We then focused on the pesticide detoxification pathway and screened out cytochrome P450 CYP736A12 as a putative gene for functional analysis. We suppressed the expression of CYP736A12 in tomato plants by virusinduced gene silencing and analyzed tissue-specific phoxim residues, oxidative stress markers, glutathione pool, GST activity and related gene expression. Silencing CYP736A12 significantly increased phoxim residue and induced oxidative stress in tomato plants, by attenuating the TM-induced increased activity of antioxidant and detoxification enzymes, redox homeostasis and transcripts of detoxification genes including CYP724B2, GSH1, GSH2, GR, GPX, GST1, GST2, GST3, and ABC. The study revealed a critical mechanism by which TM promotes the metabolism of phoxim in tomato roots, which can be useful for further understanding the Trichodermainduced xenobiotic detoxification and improving food safety.

Water is one of the most important elements affecting the growth of ornamental plants. To investigate the effects of drought stress on the growth, ornamental values, and physiological properties of Begonia semperflorens, watering treatments with 250 mL (control check, CK), 200 mL (extremely light drought, ELD), 150 mL (light drought, LD), 100 mL (moderate drought, MD), 50 mL (severe drought, SD), and 25 mL (extremely severe drought, ESD) on the B. semperflorens variety “Chao Ao” were performed in this study. As a result, compared to the control (CK), the number of flowers, leaves, and branches, leaf size, plant height, crown diameter, as well as water content, transpiration rate, net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, and chlorophyll content in leaves decreased, followed by an increased amount of drought stress. The contents of the osmotic adjustment substances, such as soluble sugar, soluble protein, proline, and betaine, were increased under drought stress. Indicators related to antioxidant activities, such as SOD activity, increased and then decreased. The POD activity, CAT activity, MDA content, and plasma membrane permeability of B. semperflorens were higher under increased drought stress than in the control condition. The APX activity decreased and then increased under drought stress. In conclusion, B. semperflorens responds to drought stress by increasing osmotic adjustment substances and antioxidant activities and reducing the water loss, growth potential, and photosynthetic rate. The correlation analysis showed that, except for APX, the drought resistance coefficients of 23 other indexes were correlated in different degrees. Therefore, this study suggests that B. semperflorens has a strong drought resistance ability, retaining high ornamental values in conditions of moderate drought stress, and can still survive under extremely high drought stress.

Pesticide overuse has led to serious global concerns regarding food safety and environmental pollution. Although the reduction of pesticide residue is critical, our knowledge about induced pesticide metabolism in plants remains fragmentary. Melatonin (N-acetyl-5-methoxytryptamine) is an effective stress-relieving agent in both animals and plants, but little is known about the melatonin signaling mechanism and its effect on pesticide metabolism in plants. Here, we found that exogenous melatonin treatment significantly reduced chlorothalonil residue by 41 % but suppression of endogenous melatonin accumulation increased chlorothalonil residue in tomato leaves. Moreover, melatonin increased photosynthesis, Fv/Fm, Calvin cycle enzyme activity, antioxidant enzyme activity, glutathione pool, and RESPIRATORY BURST HOMOLOG1 (RBOH1) expression in tomato leaves. However, the upregulation of RBOH1, CYP724B2, GST1, GST2, GSH and ABC, the increased glutathione concentrations and the activity of detoxification enzymes due to melatonin treatment were all significantly attenuated by the treatment with an NADPH oxidase inhibitor and a ROS scavenger, indicating a clear relationship between the reduction of pesticide residue and induction in detoxifying enzymes and genes upon melatonin treatment in an apoplastic H2O2-dependent manner. These results reveal that melatonin-induced reduction in chlorothalonil residue is mediated by H2O2 signaling in tomato leaves.

Chromium (Cr) is one of the toxic elements that harms all forms of life, including plants. Industrial discharges and mining largely contribute to Cr release into the soil environment. Excessive Cr pollution in arable land significantly reduces the yield and quality of important agricultural crops. Therefore, remediation of polluted soil is imperative not only for agricultural sustainability but also for food safety. Arbuscular mycorrhizal fungi (AMF) are widespread soil-borne endophytic fungi that form mutualistic relationships with the vast majority of land plants. In mycorrhizal symbiosis, AMF are largely dependent on the host plant-supplied carbohydrates and lipids, in return, AMF aid the host plants in acquiring water and mineral nutrients, especially phosphorus, nitrogen and sulfur from distant soils, and this distinguishing feature of the two-way exchange of resources is a functional requirement for such mutualism and ecosystem services. In addition to supplying nutrients and water to plants, the AMF symbiosis enhances plant resilience to biotic and abiotic stresses including Cr stress. Studies have revealed vital physiological and molecular mechanisms by which AMF alleviate Cr phytotoxicity and aid plants in nutrient acquisition under Cr stress. Notably, plant Cr tolerance is enhanced by both the direct effects of AMF on Cr stabilization and transformation, and the indirect effects of AMF symbiosis on plant nutrient uptake and physiological regulation. In this article, we summarized the research progress on AMF and associated mechanisms of Cr tolerance in plants. In addition, we reviewed the present understanding of AMF-assisted Cr remediation. Since AMF symbiosis can enhance plant resilience to Cr pollution, AMF may have promising prospects in agricultural production, bioremediation, and ecological restoration in Cr-polluted soils.

基于全长转录组测序(isoform sequencing,Iso-Seq)技术对野生马齿苋叶片(对照、干旱和低温胁迫3种处理的叶片)转录组进行测序及其转录组信息分析的结果显示,总共得到641732条原始片段,质控后得到合格的插入片段26758071条,总碱基量为44 Gb,利用CCS软件获得442760条一致性序列,根据smrtlink软件得到全长的插入片段和全长的去除嵌合体的插入片段分别为391258条和301412条,去除冗余得到103298条转录本,最终得到39717条unigene,预测出40952条LncRNA和38419条CDS序列;并将unigene与Uniprot、Pfam、GO、KEGG、eggNOG、Pathway和Nr等数据库进行同源比对,其中36381条unigene被注释,从这些unigene里查找到25898个简单重复序列标记(simple sequence repeats,SSR)位点.利用差异表达分析软件DESeq2筛选不同处理组间的差异表达基因,对照和干旱处理、对照和低温胁迫处理及干旱和低温胁迫处理间分别鉴定出16194(上调和下调差异基因分别为2874和13320)、16093(上调和下调差异基因分别为6365和9728)和25498(上调和下调差异基因分别为15163和10335)个差异表达基因.研究结果可为马齿苋属植物基因研究和SSR开发研究提供参考.

Chromium (Cr) is a toxic heavy metal for both animals and plants. The multifunctional signaling molecule melatonin can confer plant tolerance to heavy metal stress, but the mechanisms remain largely unknown. Here, we unveiled the critical role of the secondary metabolite anthocyanin in melatonin-induced Cr stress tolerance. Excess Cr caused severe phytotoxicity, which was manifested by leaf yellowing, stunted growth, reduced Fv/Fm, and increased accumulation of reactive oxygen species and malondialdehyde in a dose-dependent manner. Interestingly, leaf anthocyanin content increased under Cr stress and was the highest under 100 µM Cr (7.67-fold), while exogenous melatonin further increased anthocyanin accumulation with the highest being with 100 µM melatonin (by 90.72 %). In addition, exogenous melatonin increased endogenous melatonin content and alleviated Cr stress; however, suppression of melatonin accumulation aggravated Cr phytotoxicity and inhibited anthocyanin accumulation by downregulating the transcript levels of key structural genes. Melatonin also reduced the Cr content in roots and leaves. Crucially, suppression of anthocyanin biosynthesis by silencing an anthocyanin biosynthetic gene ANTHOCYANIDIN SYNTHASE (ANS) significantly compromised melatonin-induced anthocyanin accumulation and alleviation of Cr phytotoxicity, suggesting that anthocyanin potentially acts downstream of melatonin and its accumulation is essential for melatonin-induced Cr stress tolerance in tomato plants.

Fusarium wilt, caused by Fusarium oxysporum f. sp. cucumerinum (Fo), is a severe soil-borne disease affecting cucumber production worldwide, particularly under monocropping in greenhouses. Silicon (Si) plays an important role in improving the resistance of crops to Fusarium wilt, but the underlying mechanism is largely unclear. Here, an in vitro study showed that 3 mmol·l-1 Si had the best inhibitory effect on the mycelial growth of F. oxysporum in potato dextrose agar (PDA) culture for 7 days. Subsequently, the occurrence of cucumber wilt disease and its mechanisms were investigated upon treatments with exogenous silicon under soil culture. The plant height, stem diameter, root length, and root activity under Si+Fo treatment increased significantly by 39.53%, 94.87%, 74.32%, and 95.11% compared with Fo only. Importantly, the control efficiency of Si+Fo was 69.31% compared with that of Fo treatment. Compared with Fo, the activities of peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) significantly increased by 148.92%, 26.47%, and 58.54%, while the contents of H2O2, O2·−, and malondialdehyde (MDA) notably decreased by 21.67%, 59.67%, and 38.701%, respectively, in roots of cucumber plants treated with Si + Fo. Compared with Fo treatment, the net photosynthesis rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), maximum RuBisCO carboxylation rates (Vcmax), maximum RuBP regeneration rates (Jmax), and activities of ribulose-1,5-bisphosphate carboxylase (RuBisCO), fructose-1,6-bisphosphatase (FBPase), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and the expression of FBPA, TPI, SBPase, and FBPase in Si+Fo treatment increased significantly. Furthermore, Si alleviated stomatal closure and enhanced endogenous silicon content compared with only Fo inoculation. The study results suggest that exogenous silicon application improves cucumber resistance to Fusarium wilt by stimulating the antioxidant system, photosynthetic capacity, and stomatal movement in cucumber leaves. This study brings new insights into the potential of Si application in boosting cucumber resistance against Fusarium wilt with a bright prospect for Si use in cucumber production under greenhouse conditions.

Trichoderma harzianum (TM) is a soil-borne beneficial fungus that positively affects plant growth and defense. TM shows antagonism against multiple plant pathogens; however, the TM as a biocontrol agent against Botrytis cinerea (BC) and underlying mechanisms remain unclear. Herein we studied the effects of TM on BC by dual-culture assay and greenhouse bioassay in tomato plants. In vitro experiments showed that TM rapidly occupied most of the nutrient space and eventually covered BC on potato dextrose agar (PDA) medium. The TM inhibition rate against BC was 62.05% on the sixth day of culture. The inhibitory effect of TM spore suspension on gray mold inoculated with spore suspension and solid inoculants was 33.66% and 69.44%, respectively in tomato plants. Notably, TM decreased the leaf concentrations of BC-induced hydrogen peroxide and malondialdehyde but improved the redox state. TM inoculation caused biphasic peaks in the expression of secondary metabolism and defense-related genes and increased the concentrations of flavonoids, phenols and lignin in tomato leaves. Moreover, TM alleviated stomatal closure and enhanced the net photosynthesis rate and the activity of RuBisCO and FBPase compared with only BC inoculation. Our results suggest that TM spore suspension improves tomato resistance to gray mold disease by stimulating cellular redox, secondary metabolites and stomatal movement.

Heavy metal pollution not only decreases crop yield and quality, but also affects human health via the food chain. Ubiquitination-dependent protein degradation is involved in plant growth, development, and environmental interaction, but the functions of ubiquitin-ligase (E3) genes are largely unknown in tomato (Solanum lycopersicum L.). Here, we functionally characterized a RING E3 ligase gene, SlRING1, which positively regulates cadmium (Cd) tolerance in tomato plants. An in vitro ubiquitination experiment shows that SlRING1 has E3 ubiquitin ligase activity. The determination of the subcellular localization reveals that SlRING1 is localized at both the plasma membrane and the nucleus. Overexpression of SlRING1 in tomato increased the chlorophyll content, the net photosynthetic rate, and the maximal photochemical efficiency of photosystem II (Fv/Fm), but reduced the levels of reactive oxygen species and relative electrolyte leakage under Cd stress. Moreover, SlRING1 overexpression increased the transcript levels of CATALASE (CAT), DEHYDROASCORBATE REDUCTASE (DHAR), MONODEHYDROASCORBATE REDUCTASE (MDHAR), GLUTATHIONE (GSH1), and PHYTOCHELATIN SYNTHASE (PCS), which contribute to the antioxidant and detoxification system. Crucially, SlRING1 overexpression also reduced the concentrations of Cd in both shoots and roots. Thus, SlRING1-overexpression-induced enhanced tolerance to Cd is ascribed to reduced Cd accumulation and alleviated oxidative stress. Our findings suggest that SlRING1 is a positive regulator of Cd tolerance, which can be a potential breeding target for improving heavy metal tolerance in horticultural crops.