Pathogenesis-related Protein Genes Research Articles

Enhancement of broad-spectrum disease resistance in wheat through key genes involved in systemic acquired resistance.

Systemic acquired resistance (SAR) is an inducible disease resistance phenomenon in plant species, providing plants with broad-spectrum resistance to secondary pathogen infections beyond the initial infection site. In Arabidopsis, SAR can be triggered by direct pathogen infection or treatment with the phytohormone salicylic acid (SA), as well as its analogues 2,6-dichloroisonicotinic acid (INA) and benzothiadiazole (BTH). The SA receptor non-expressor of pathogenesis-related protein gene 1 (NPR1) protein serves as a key regulator in controlling SAR signaling transduction. Similarly, in common wheat (Triticum aestivum), pathogen infection or treatment with the SA analogue BTH can induce broad-spectrum resistance to powdery mildew, leaf rust, Fusarium head blight, and other diseases. However, unlike SAR in the model plant Arabidopsis or rice, SAR-like responses in wheat exhibit unique features and regulatory pathways. The acquired resistance (AR) induced by the model pathogen Pseudomonas syringae pv. tomato strain DC3000 is regulated by NPR1, but its effects are limited to the adjacent region of the same leaf and not systemic. On the other hand, the systemic immunity (SI) triggered by Xanthomonas translucens pv. cerealis (Xtc) or Pseudomonas syringae pv. japonica (Psj) is not controlled by NPR1 or SA, but rather closely associated with jasmonate (JA), abscisic acid (ABA), and several transcription factors. Furthermore, the BTH-induced resistance (BIR) partially depends on NPR1 activation, leading to a broader and stronger plant defense response. This paper provides a systematic review of the research progress on SAR in wheat, emphasizes the key regulatory role of NPR1 in wheat SAR, and summarizes the potential of pathogenesis-related protein (PR) genes in genetically modifying wheat to enhance broad-spectrum disease resistance. This review lays an important foundation for further analyzing the molecular mechanism of SAR and genetically improving broad-spectrum disease resistance in wheat.

Transcriptome analysis of resistant and susceptible grapes reveals molecular mechanisms underlying resistance of white rot disease

Grape production in China is significantly impacted by white rot disease, which is caused by Coniella diplodiella (Speg.) Sacc. This study analyzes the differences in leaf transcriptomes and phenotypes of two grape species, ‘Manicure Finger (Vitis vinifera L.)’ and ‘0940 (Vitis davidii Foex)’, following inoculation with C. diplodiella. Leaf anatomy and H2O2 content confirm the greater resistance of '0940' to C. diplodiella compared to 'Manicure Finger.' Comparative transcriptome analysis reveals that the defense mechanism of '0940' against C. diplodiella involves sesquiterpenoid and triterpenoid biosynthesis, plant-pathogen interactions, sulfur relay systems, suberin and wax biosynthesis, monoterpenoid biosynthesis, as well as flavonoid and flavonol biosynthesis pathways. Using Weighted Gene Co-expression Network Analysis (WGCNA), we identified three modules highly correlated with C. diplodiella resistance and 125 candidate genes, including resistant genes (R genes), pattern-recognition receptors (PRRs), and pathogenesis-related proteins genes (PR genes), which may play important roles in grape resistance to this disease.

Turmeric (Curcuma longa L.) rhizome extract mediated silver nanoformulation exhibits enhanced antifungal property against Rhizoctonia solani and boosts innate immunity of rice

Aqueous extract of turmeric rhizomes exhibits antifungal properties against Rhizoctonia solani at higher concentrations. Nanotechnology offers innovative strategies to improve the antifungal potency of the extract. An eco-friendly green synthesis technique was used to formulate silver nanoparticles from turmeric rhizome extract (SNPTs) and characterized by UV–VIS spectrophotometer, dynamic light scattering (DLS), field emission scanning electron microscope (FESEM) and fourier transform infrared spectrometer (FTIR). 100 ppm SNPTs can inhibit the growth of Rhizoctonia solani up to 82% in vitro and 77% in vivo. SNPT-treated fungal mycelia had a 1.5-fold higher reactive oxygen species (ROS) accumulation and a 2-fold decrease in mitochondrial membrane potential (MMP) with elevated cytochrome oxidase 3 (COX 3) and NADH dehydrogenase 5 (NAD 5) (2 and 5.25-fold up-regulation) expression. SNPT nano-primed rice seedlings exhibited enhanced phenylalanine ammonia lyase (PAL), peroxidase (POX), and superoxide dismutase (SOD) activity with up-regulation of phenylalanine ammonia lyase (PAL) and pathogenesis-related protein (PR-protein) gene expression. Nano-primed rice seedlings have a sturdy root system with 2.5-fold more callose accumulation. Taken together, the results suggest SNPT inhibits Rhizoctonia and boosts plant innate immunity simultaneously to acquire resistance against the fungal pathogen.

Transcriptome Analysis of Early Pathogenetic Responsive Genes in Cavendish Bananas During Fusarium oxysporum f. sp. Cubense Race 1 and Race 4 Infection

Banana Fusarium wilt is a devastating banana disease caused by Fusarium oxysporum f. sp. cubense (Foc), seriously threatening the global banana industry. However, knowledge of the molecular mechanisms of pathogenicity and the interaction between the host and Foc is limited. In this study, we confi rmed the changes in gene expression and pathways in the Cavendish banana variety “Brazilian” during early infection with Foc1 and Foc4 by comparative transcriptomic analysis, including pathogenesisrelated protein genes, leucine-rich repeat type genes, and plant hormone genes. In the early stages of Foc inoculation, more differentially expressed genes were identifi ed in roots infected with Foc1 than in those infected with Foc4. According to Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses, bananas with Foc1 infection caused differential accumulation and expression of various defence-related compounds and genes at the early stage of infection. In contrast, changes in the expression of defence-related genes in the early stages of Foc4 infection were small or weak and were not apparent until 24 h post-infection. Therefore, plant immune responses may occur at this stage of infection. This study could help clarify the interaction between banana plants and Foc and develop control measures for banana Fusarium wilt.

Potential of resistance inducers for citrus huanglongbing management via soil application and assessment of induction of pathogenesis-related protein genes

Huanglongbing (HLB) or citrus greening currently is the most devastating citrus disease worldwide. Unfortunately, no practical cure has been available up to now. This makes the control of HLB as early as possible very important to be conducted. The objective of this study was to investigate the efficacy of the application of salicylic acid (SA) and Phenylacetic acid (PAA) on one-year-old seedlings of different citrus species (Citrus reticulata, C. sinensis, C. aurantifolii) growing on C. volkameriana and C. aurantium by soil drench methods. Factorial analysis of variance showed the percent change in “Candidatus Liberibacter asiaticus” titer and disease severity on a different combination of citrus species growing on the two rootstocks treated with inducers and Oxytetracycline (OTC) were significantly different compared to the untreated plants. SA alone or in combination with OTC provided excellent (P-value < 0.05) control of HLB based on all parameters. The interaction between both factors (Rootstocks x Citrus species) significantly influenced the Ct value (P-value = 0.0001). “Candidatus Liberibacter asiaticus” titer in plants treated with OTC was reduced significantly with a range of −18.75 up to −78.42. Overall, the highest reduction was observed in the application of OTC on sweet orange growing on C. volkameriana (−78.42), while the lowest reduction was observed in the same cultivar which was treated with a combination of SA and OTC (−3.36). Induction of pathogenesis-related (PR) genes, i.e., PR1, PR2, and PR15, biosynthesis of Jasmonic acid and ethylene which are also important pathways to defense activity were also significantly increased in treated plants compared to untreated plants. This study suggests that the application of inducer alone is acceptable for HLB management. We proposed the application of SA and PAA as a soil drench on the citrus seedlings as promising, easy, and environmentally safe for HLB disease control on citrus seedlings.

Tissues and mechanisms associated with Verticillium wilt resistance in tomato using bi-grafted near-isogenic lines.

Host resistance is the primary means to control Verticillium dahliae, a soil-borne pathogen causing major losses on a broad range of plants, including tomato. The tissues and mechanisms responsible for resistance remain obscure. In the field, resistant tomato used as rootstocks does not confer resistance. Here, we created bi-grafted plants with near-isogenic lines (NILs) exhibiting (Ve1) or lacking (ve1) resistance to V. dahliae race 1. Ten days after inoculation, scion and rootstock tissues were subjected to differential gene expression and co-expression network analyses. Symptoms only developed in susceptible scions regardless of the rootstock. Infection caused more dramatic alteration of tomato gene expression in susceptible compared to resistant tissues, including pathogen receptor, signaling pathway, PR protein, and cell wall modification genes. Differences were observed between scions and rootstocks, primarily related to physiological processes in these tissues. Gene expression in scions was influenced by the rootstock genotype. A few genes were associated with the Ve1 genotype, which was independent of infection or tissue type. Several were physically clustered, some near the Ve1 locus on chromosome 9. Transcripts mapped to V. dahliae were dominated by secreted candidate effector proteins. These findings advance knowledge of molecular mechanisms underlying the tomato-V. dahliae interaction.

Integrative transcriptome and proteome analysis reveals maize responses to Fusarium verticillioides infection inside the stalks.

Fusarium stalk rot caused by Fusarium verticillioides is one of the most devastating diseases of maize that causes significant yield losses and poses potential security concerns for foods worldwide. The underlying mechanisms of maize plants regulating defence against the disease remain poorly understood. Here, integrative proteomic and transcriptomic analyses were employed to identify pathogenesis-related protein genes by comparing differentially expressed proteins (DEPs) and differentially expressed genes (DEGs) in maize stalks after inoculation with F.verticillioides. Functional enrichment analysis showed that DEGs and DEPs were mainly enriched in glutathione metabolism, starch and sucrose metabolism, amino sugar and nucleotide sugar metabolism, linoleic acid metabolism, and phenylpropanoid biosynthesis. Fourteen DEGs and DEGs that were highly elevated after inoculation with F.verticillioides were confirmed with parallel reaction monitoring and reverse transcription-quantitative PCR, demonstrating the accountability and reliability of proteomic and transcriptomic data. We also assessed the potential roles of defence-related genes ZmCTA1, ZmWIP1, and ZmLOX2, identified from the multi-omics analysis, during the process of F.verticillioides infection through virus-induced gene silencing. The elevation of stalk rot symptomatic characteristics in the silenced plants revealed their contribution to resistance. We further functionally characterized the roles of ZmLOX2 expression in the defence response of maize plants conditioning fungal invasion via the salicylic acid-dependent pathway. Collectively, this study provides a comprehensive analysis of transcriptome and proteome of maize stalks following F.verticillioides inoculation, and defence-related genes that could inform selection of new genes as targets in breeding strategies.

SlWRKY30 and SlWRKY81 synergistically modulate tomato immunity to Ralstonia solanacearum by directly regulating SlPR-STH2.

Bacterial wilt is a devastating disease of tomato (Solanum lycopersicum) caused by Ralstonia solanacearum that severely threatens tomato production. Group III WRKY transcription factors (TFs) are implicated in the plant response to pathogen infection; however, their roles in the response of tomato to R. solanacearum infection (RSI) remain largely unexplored. Here, we report the crucial role of SlWRKY30, a group III SlWRKY TF, in the regulation of tomato response to RSI. SlWRKY30 was strongly induced by RSI. SlWRKY30 overexpression reduced tomato susceptibility to RSI, and also increased H2O2 accumulation and cell necrosis, suggesting that SlWRKY30 positively regulates tomato resistance to RSI. RNA sequencing and reverse transcription-quantitative PCR revealed that SlWRKY30 overexpression significantly upregulated pathogenesis-related protein (SlPR-STH2) genes SlPR-STH2a, SlPR-STH2b, SlPR-STH2c, and SlPR-STH2d (hereafter SlPR-STH2a/b/c/d) in tomato, and these SlPR-STH2 genes were directly targeted by SlWRKY30. Moreover, four group III WRKY proteins (SlWRKY52, SlWRKY59, SlWRKY80, and SlWRKY81) interacted with SlWRKY30, and SlWRKY81 silencing increased tomato susceptibility to RSI. Both SlWRKY30 and SlWRKY81 activated SlPR-STH2a/b/c/d expression by directly binding to their promoters. Taking these results together, SlWRKY30 and SlWRKY81 synergistically regulate resistance to RSI by activating SlPR-STH2a/b/c/d expression in tomato. Our results also highlight the potential of SlWRKY30 to improve tomato resistance to RSI via genetic manipulations.

Towards Marker-Assisted Breeding for Black Rot Bunch Resistance: Identification of a Major QTL in the Grapevine Cultivar 'Merzling'.

Black rot (BR), caused by Guignardia bidwellii, is an emergent fungal disease threatening viticulture and affecting several mildew-tolerant varieties. However, its genetic bases are not fully dissected yet. For this purpose, a segregating population derived from the cross 'Merzling' (hybrid, resistant) × 'Teroldego' (V. vinifera, susceptible) was evaluated for BR resistance at the shoot and bunch level. The progeny was genotyped with the GrapeReSeq Illumina 20K SNPchip, and 7175 SNPs were combined with 194 SSRs to generate a high-density linkage map of 1677 cM. The QTL analysis based on shoot trials confirmed the previously identified Resistance to Guignardia bidwellii (Rgb)1 locus on chromosome 14, which explained up to 29.2% of the phenotypic variance, reducing the genomic interval from 2.4 to 0.7 Mb. Upstream of Rgb1, this study revealed a new QTL explaining up to 79.9% of the variance for bunch resistance, designated Rgb3. The physical region encompassing the two QTLs does not underlie annotated resistance (R)-genes. The Rgb1 locus resulted enriched in genes belonging to phloem dynamics and mitochondrial proton transfer, while Rgb3 presented a cluster of pathogenesis-related Germin-like protein genes, promoters of the programmed cell death. These outcomes suggest a strong involvement of mitochondrial oxidative burst and phloem occlusion in BR resistance mechanisms and provide new molecular tools for grapevine marker-assisted breeding.

Verticillium dahliae Vta3 promotes ELV1 virulence factor gene expression in xylem sap, but tames Mtf1-mediated late stages of fungus-plant interactions and microsclerotia formation.

Verticillium transcription activator of adhesion 3 (Vta3) is required for plant root colonization and pathogenicity of the soil-borne vascular fungus Verticillium dahliae. RNA sequencing identified Vta3-dependent genetic networks required for growth in tomato xylem sap. Vta3 affects the expression of more than 1,000 transcripts, including candidates with predicted functions in virulence and morphogenesis such as Egh16-like virulence factor 1 (Elv1) and Master transcription factor 1 (Mtf1). The genes encoding Elv1 and Mtf1 were deleted and their functions in V. dahliae growth and virulence on tomato (Solanum lycopersicum) plants were investigated using genetics, plant infection experiments, gene expression studies and phytohormone analyses. Vta3 contributes to virulence by promoting ELV1 expression, which is dispensable for vegetative growth and conidiation. Vta3 decreases disease symptoms mediated by Mtf1 in advanced stages of tomato plant colonization, while Mtf1 induces the expression of fungal effector genes and tomato pathogenesis-related protein genes. The levels of pipecolic and salicylic acids functioning in tomato defense signaling against (hemi-) biotrophic pathogens depend on the presence of MTF1, which promotes the formation of resting structures at the end of the infection cycle. In summary, the presence of VTA3 alters gene expression of virulence factors and tames the Mtf1 genetic subnetwork for late stages of plant disease progression and subsequent survival of the fungus in the soil.

Molecular Genetic Mechanisms of Heterosis in Sugarcane Cultivars Using a Comparative Transcriptome Analysis of Hybrids and Ancestral Parents

Modern sugarcane cultivars (Saccharum spp. hybrids) are the major contributors to sucrose and bioenergy in the world. The global changes in gene expression and the molecular mechanism of heterosis between modern sugarcane hybrids and their parents remain to be elucidated. In this study, we performed a comparative transcriptome analysis between hybrids and their parents using the Illumina RNA-Seq method to understand the differences in transcript expression after hybridization. The results show that (1) introduction of the S. spontaneum lineage resulted in significant upregulation of biotic and abiotic stress resistance genes in S. hybrids, including hexokinase (HXK) genes, pathogenesis-related protein (PR1) genes, coronatine-insensitive protein (COI-1), jasmonate ZIM domain-containing protein (JAZ) genes, and serine/threonine protein kinase 2 (SnRK2) genes. (2) Transgressive genes in hybrids were mainly concentrated in the synthesis pathways of biotin and vitamin B6, helping establish advantages in terms of stress resistance, antioxidant activity, and growth. (3) Glutathione-S-transferase (GST) was likely to enhance stress resistance in hybrids, and corresponding genes were key positive selection genes in processes, including round-robin selection and other adaptations. In this study, we propose explanations for heterosis in sugarcane hybrids from a transcriptomic perspective, in addition to identifying candidate genes to aid in the improvement of sugarcane cultivars.

Full-Length Transcriptome Characterization and Functional Analysis of Pathogenesis-Related Proteins in Lilium Oriental Hybrid 'Sorbonne' Infected with Botrytis elliptica.

Gray mold (Botrytis elliptica) causes a deleterious fungal disease that decreases the ornamental value and yield of lilies. Lilium oriental hybrid 'Sorbonne' is a variety that is resistant to gray mold. Understanding the mechanism of resistance against B. elliptica infection in 'Sorbonne' can provide a basis for the genetic improvement in lily plants. In this study, a PacBio Sequel II system was used to sequence the full-length transcriptome of Lilium 'Sorbonne' after inoculation with B. elliptica. A total of 46.64 Gb subreads and 19,102 isoforms with an average length of 1598 bp were obtained. A prediction analysis revealed 263 lncRNAs, and 805 transcription factors, 4478 simple sequence repeats, and 17,752 coding sequences were identified. Pathogenesis-related proteins (PR), which may play important roles in resistance against B. elliptica infection, were identified based on the full-length transcriptome data and previously obtained second-generation transcriptome data. Nine non-redundant potential LhSorPR proteins were identified and assigned to two groups that were composed of two LhSorPR4 and seven LhSorPR10 proteins based on their genetic relatedness. The real-time quantitative reverse transcription PCR (qRT-PCR) results showed that the patterns of expression of nine differentially expressed PR genes under B. elliptica stress were basically consistent with the results of transcriptome sequencing. The pattern of expression of LhSorPR4s and LhSorPR10s genes in different tissues was analyzed, and the expression of each gene varied. Furthermore, we verified the function of LhSorPR4-2 gene in Lilium. The expression of LhSorPR4-2 was induced by phytohormones such as methyl jasmonate, salicylic acid, and ethephon. Moreover, the promoter region of LhSorPR4-2 was characterized by several functional domains associated with phytohormones and stress response. The overexpression of LhSorPR4-2 gene in 'Sorbonne' increased the resistance of the lily plant to B. elliptica and correlated with high chitinase activity. This study provides a full-length transcript database and functionally analyzed the resistance of PR gene to B. elliptica in Lilium, thereby introducing the candidate gene LhSorPR4-2 to breed resistance in Lilium.

Isolation and characterization of a pathogenesis-related protein 1 (SlPR1) gene with induced expression in tomato (Solanum lycopersicum) during Ralstonia solanacearum infection

In order to explore the function of pathogenesis-related (PR) proteins in regulating tomato (Solanum lycopersicum) biological stress response, a PR protein gene (SlPR1) (Gen ID: Solyc01g106620.2) was isolated from tomato by RT-PCR. The full-length cDNA was 760 bp, which encoded a total of 179 amino acids. The cDNA contained a 42 bp 5′ non-coding region, a 178 bp 3′ non-coding region, and an open reading frame (ORF) of 540 bp. Homologous sequence alignment and phylogenetic analysis indicated that SlPR1 was highly homologous with a S. tuberosum PR1 protein, followed by S. pennellii. The predicted molecular weight of SlPR1 was 20,123.47 Da, the isoelectric point was 8.48, and the protein was found to be a secreted protein with a transmembrane structure. Quantitative real-time PCR (qRT-PCR) revealed that SlPR1 gene expression was highest in tomato stems, and could be induced by infection with Ralstonia solanacearum, and treatment with salicylic acid (SA) and methyl jasmonate acid (MeJA).Virus-induced gene silencing (VIGS) of SlPR1 decreased plant resistance to bacterial wilt, suggesting that SlPR1 positively regulates tomato resistance to this disease.This study provides a reference for the further exploration of the role of SlPR1 in the response of tomato to bacterial wilt and other stressors.

Penicillium simplicissimum and Trichoderma asperellum counteract the challenge of Puccinia striiformis f. sp. tritici in wheat plants

BackgroundYellow (stripe) rust, caused by Puccinia striiformis f. sp. tritici (Pst), is an economic disease of wheat. Growth-promoting fungi (GPF) such as Trichoderma asperellum and Penicillium simplicissimum have been investigated for their potential to control yellow rust and their involvement in gene expression of four PR proteins for all-stage resistance.ResultsWheat plants (cv. Sids-12) treated individually with each of the biocontrol agents, P. simplicissimum and T. asperellum, at 24 and 48 hpi showed a resistance response (infection type = 2) to yellow rust, compared to the non-treated plants, which showed highly susceptible response (infection type = 9). Both biocontrol agents induced resistance against yellow rust on wheat plants, exhibiting a moderate resistance (10 MR) and reduced the colony size of Pst (0.6 mm2). Moreover, P. simplicissimum and T. asperellum increased (P ≤ 0.05) the grain yields of wheat plants infected with Pst. Scanning electron microscope (SEM) of yellow rust infected wheat leaves treated with P. simplicissimum and T. asperellum at 24 and 48 hpi showed hyperparasitism on Pst urediniospores and inhibition of the spore germination. Expressions of pathogenesis-related (PR) protein genes, PR1, PR2, PR3 and PR4 were higher in wheat plants treated with both biocontrol agents than the non-treated checks.ConclusionP. simplicissimum and T. asperellum exhibited biocontrol potential against yellow rust disease caused by P. striiformis f. sp. tritici (Pst) on wheat plants. It was found that wheat defence mechanism against Pst was activated by a high expression of PR protein genes induced by both biocontrol agents.

Efficiency of plant growth regulators as inducers for improve systemic acquired resistance against stripe rust disease caused by Puccinia striiformis f. sp. tritici in wheat through up-regulation of PR-1 and PR-4 genes expression

Systemic acquired resistance (SAR) induced by five different phytohormones (plant growth regulators); salicylic acid (SA), abscisic acid (ABA), indole 3-butyric acid (IBA), indoleacetic acid (IAA) and naphthaleneacetic acid (NAA) was investigated against Puccinia striiformis f. sp. tritici (pst) in the Egyptian susceptible wheat genotype Sids-12. Seedlings were sprayed with three different concentrations of each phytohormones and inoculated by uredospore of pst then evaluated against the germination. Results indicated that, all the five chemical inducers were able to inhibit spore germination and showed highly significant differences among treatments, while, ABA and NAA recorded the lowest germination and the highest inhibition percentages at the low concentration (50 μg/ml). Also, all treatments reduced infection type values and numbers of pustules/leaf compared with control (untreated treatment). ABA treatment at concentration of 50 μg/ml was capable to induce complete protection for the susceptible wheat cultivar, Sids-12 by significant reduction of infection type (0) compared with control. On the other side, relative gene expression of two pathogenesis-related (PR) protein genes; the antifungal protein (PR-1) and the endochitinase (PR-4) were evaluated for the treated seedlings in all treatments at three different time points comparing with untreated plants and the resistant wheat genotype Misr-3. Results showed up-regulation of gene expressions in all treatments for the two tested genes at the three time points (1, 2 and 7 days after inoculation) comparing with control and most of treatments comparing with the resistant genotype Misr-3. This over expression of PR protein genes might be definitive in activation of the host defense mechanism against Pst and playing the important role of resistance induced by chemical inducers as phytohormones in wheat. Also, it was found that ABA treatment was more efficient in inducing the resistance to wheat stripe rust disease than other chemical inducers. The obtained results indicated that phytohormones as inducers can be used to management stripe rust disease in wheat.

Influence of peanut hairy root cultivars on prenylated stilbenoid production and the response mechanism for combining the elicitors of chitosan, methyl jasmonate, and cyclodextrin

Peanut cultivars are known to produce stilbene compounds. Transcriptional control plays a key role in the early stages of the stress response mechanism, involving both PR-proteins and stilbene compounds. In this study, the production of stilbenoid compounds, especially prenylated, was investigated in two cultivars of peanut hairy root lines, designated as K2-K599 and T9-K599 elicited with a combination of chitosan (CHT), methyl jasmonate (MeJA), and cyclodextrin (CD): CHT + MeJA + CD. The antioxidant activities and stilbenoid content of both K2-K599 and T9-K599 hairy root lines increased significantly during the elicitation period. The T9-K599 hairy root line expressed higher ABTS and FRAP antioxidant activities than the K2-K599 line while the latter exhibited greater total phenolic content than the former at all-time points. Additionally, the K2-K599 line exhibited more stilbene compounds, including trans-resveratrol, trans-arachidin-1, and trans-arachidin-3 than the T9-K599 line, which showed statistically significant differences at all-time points. Gene expression of the enzyme involved in the stilbene biosynthesis pathway (PAL, RS, RS3) was observed, responding early to elicitor treatment and the metabolic production of a high level of stilbenoid compounds at a later stage. The antioxidant enzyme (CuZn-SOD, APX, GPX) and pathogenesis-related protein (PR; PR4A, PR5, PR10, chitinase) genes were strongly expressed after elicitor treatment at 24h and decreased with an increasing elicitation time. Investigation of the response mechanism illustrates that the elicitor treatment can affect various plant responses, including plant cell wall structure and integrity, antioxidant system, PR-proteins, and secondary plant metabolites at different time points after facing external environmental stimuli.

Synergistic Effect of Melatonin and Selenium Improves Resistance to Postharvest Gray Mold Disease of Tomato Fruit.

Melatonin (MT) is a ubiquitous hormone molecule that is commonly distributed in nature. MT not only plays an important role in animals and humans but also has extensive functions in plants. Selenium (Se) is an essential micronutrient for animals and humans, and is a beneficial element in higher plants at low concentrations. Postharvest diseases caused by fungal pathogens lead to huge economic losses worldwide. In this study, tomato fruits were treated with an optimal sodium selenite (20 mg/L) and melatonin (10 μmol/L) 2 h and were stored for 7 days at room temperature simulating shelf life, and the synergistic effects of Se and MT collectively called Se-Mel on gray mold decay in tomato fruits by Botrytis cinerea was investigated. MT did not have antifungal activity against B. cinerea in vitro, while Se significantly inhibited gray mold development caused by B. cinerea in tomatoes. However, the interaction of MT and Se showed significant inhibition of the spread and growth of the disease, showing the highest control effect of 74.05%. The combination of MT with Se treatment enhanced the disease resistance of fruits by improving the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), as well as increasing the gene expression level of pathogenesis-related (PR) proteins. Altogether, our results indicate that the combination of MT and Se would induce the activation of antioxidant enzymes and increase the expression of PR proteins genes that might directly enhance the resistance in tomato fruit against postharvest pathogenic fungus B. cinerea.

Transcriptome analysis revealed that jasmonic acid biosynthesis/signaling is involved in plant response to Strontium stress

Strontium (Sr) has become an increasing global threat for both environment and human health due to its radioactive isotope, Sr-90 which can be found in the nuclear-contaminated soils and water. Although excessive Sr has been known to be toxic to plant growth and development, the molecular mechanisms underlying plant response to Sr stress, especially on the transcription level, remains largely unknown. To date, there is no published genome-wide transcriptome data available for the plant responses to Sr toxicity. Therefore, we aimed to gain insight on the molecular events occurring in plants in Sr toxicity condition by comparing the genome-wide gene expression profiles between control and Sr-treated plants using RNA-seq analysis. A total of 842 differentially expressed genes (DEGs) were identified in response to Sr stress compared to the control. Based on the analysis of DEGs using Gene Ontology (GO), DEGs were significantly enriched in the GO terms of response to salicylic acid (SA), response to jasmonic acid (JA), and defense response to bacterium. In addition, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis indicated that DEGs were mainly involved in metabolic processes including phenylpropanoid biosynthesis and alpha-linolenic acid metabolism, which is known as a precursor of JA biosynthesis. Furthermore, MapMan analysis revealed that a number of genes related to the biotic stress such as pathogenesis-related protein (PR) genes were highly up-regulated under Sr stress. Taken together, this study revealed that JA biosynthesis and/or signaling might be associated with plant response to Sr stress, and play important roles to maintain proper growth and development under Sr stress.

Trichoderma asperelloides PSU-P1 Induced Expression of Pathogenesis-Related Protein Genes against Gummy Stem Blight of Muskmelon (Cucumis melo) in Field Evaluation

Gummy stem blight caused by Stagonosporopsis cucurbitacearum is the most destructive disease of muskmelon cultivation. This study aimed to induce disease resistance against gummy stem blight in muskmelon by Trichoderma asperelloides PSU-P1. This study was arranged into two crops. Spore suspension at a concentration of 1 × 106 spores/mL of T. asperelloides PSU-P1 was applied to muskmelon to investigate gene expression. The expression of PR genes including chitinase (chi) and β-1,3-glucanase (glu) were determined by reverse transcription quantitative polymerase chain reaction (RT-qPCR), and enzyme activity was assayed by the DNS method. The effects of T. asperelloides PSU-P1 on growth, yield, and postharvest quality of muskmelon fruit were measured. A spore suspension at a concentration of 1 × 106 spore/mL of T. asperelloides PSU-P1 and S. cucurbitacearum was applied to muskmelons to determine the reduction in disease severity. The results showed that the expression of chi and glu genes in T. asperelloides PSU-P1-treated muskmelon plants was 7–10-fold higher than that of the control. The enzyme activities of chitinase and β-1,3-glucanase were 0.15–0.284 and 0.343–0.681 U/mL, respectively, which were higher than those of the control (pathogen alone). Scanning electron microscopy revealed crude metabolites extracted from T. asperelloides PSU-P1-treated muskmelon plants caused wilting and lysis of S. cucurbitacearum hyphae, confirming the activity of cell-wall-degrading enzymes (CWDEs). Application of T. asperelloides PSU-P1 increased fruit weight and fruit width; sweetness and fruit texture were not significantly different among treated muskmelons. Application of T. asperelloides PSU-P1 reduced the disease severity scale of gummy stem blight to 1.10 in both crops, which was significantly lower than that of the control (2.90 and 3.40, respectively). These results revealed that application of T. asperelloides PSU-P1 reduced disease severity against gummy stem blight by overexpressed PR genes and elevated enzyme activity in muskmelon plants.

First Report of Protective Activity of Paronychia argentea Extract against Tobacco Mosaic Virus Infection

The widespread use of chemical control agents and pesticides for plant-pathogen control has caused many human health and environmental issues. Plant extracts and biocontrol agents have robust antimicrobial activity against different plant pathogens. However, their antiviral activities are still being investigated. In the present study, the methanol extract of Paronychia argentea was characterized and evaluated for its protective activity against the tobacco mosaic virus (TMV) infection in tomato plants under greenhouse conditions at 21 days post-inoculation. The results showed that the foliar application of P. argentea extract (10 µg/mL) enhanced tomato plant growth, resulting in significant increases in shoot and root parameters and total chlorophyll contents. Moreover, a significant reduction in TMV accumulation level in P. argentea-treated plants of 77.88% compared to non-treated plants was reported. Furthermore, induction of systemic resistance with significant elevation in production of antioxidant enzymes (PPO, CAT, and SOD) and transcriptional levels of the pathogenesis-related proteins (PR-1 and PR-7) and polyphenolic genes (CHS and HQT) were also observed. Out of 16 detected compounds, HPLC analysis revealed that the most abundant polyphenolic compounds found in P. argentea extract were gallic acid (5.36 µg/mL), kaempferol (7.39 µg/mL), quercetin (7.44 µg/mL), ellagic acid (7.89 µg/mL), myricetin (8.36 µg/mL), and ferulic acid (8.69 µg/mL). The findings suggest that the use of P. argentea extract as an effective and safe source for the production of bioactive compounds may offer a solution for a promising approach for the management of plant viral infections. To the best of our knowledge, this is the first report of the protective activity of P. argentea extract against plant viral diseases.