Phenylalanine increases chrysanthemum flower immunity against Botrytis cinerea attack

Preharvest spraying of phenylalanine activates the sucrose and respiratory metabolism in muskmelon wounds during healing

Phenylalanine (Phe) accelerates fruit wound healing by activating phenylpropanoid metabolism. However, whether Phe affects sucrose and respiratory metabolism in fruit during wound healing remains unknown. In this research, we found that preharvest Phe spray promoted sucrose degradation and increased glucose and fructose levels by activating acid invertase (AI), neutral invertase (NI), sucrose synthase (SS) and sucrose phosphate synthase (SPS) on harvested muskmelons. The spray also activated hexokinase (HK), phosphofructokinase (PFK), pyruvate kinase (PK), malate dehydrogenase (MDH), succinate dehydrogenase (SDH) and glucose-6-phosphate dehydrogenase (G6PDH). In addition, the spray improved energy and reducing power levels in the fruit. Taken together, preharvest Phe spray can provide carbon skeleton, energy and reducing power for wound healing by activating the sucrose metabolism, Embden-Meyerhof-Parnas (EMP) pathway, tricarboxylic acid (TCA) cycle and pentose phosphate (PPP) pathway in muskmelon wounds during healing, which is expected to be developed as a new strategy to accelerate fruit wound healing.

Modelling metabolic fluxes of tomato stems reveals that nitrogen shapes central metabolism for defence against Botrytis cinerea

Among plant pathogens, the necrotrophic fungus Botrytis cinerea is one of the most prevalent, leading to severe crop damage. Studies related to its colonization of different plant species have reported variable host metabolic responses to infection. In tomato, high N availability leads to decreased susceptibility. Metabolic flux analysis can be used as an integrated method to better understand which metabolic adaptations lead to effective host defence and resistance. Here, we investigated the metabolic response of tomato infected by B. cinerea in symptomless stem tissues proximal to the lesions for 7 d post-inoculation, using a reconstructed metabolic model constrained by a large and consistent metabolic dataset acquired under four different N supplies. An overall comparison of 48 flux solution vectors of Botrytis- and mock-inoculated plants showed that fluxes were higher in Botrytis-inoculated plants, and the difference increased with a reduction in available N, accompanying an unexpected increase in radial growth. Despite higher fluxes, such as those involved in cell wall synthesis and other pathways, fluxes related to glycolysis, the tricarboxylic acid cycle, and amino acid and protein synthesis were limited under very low N, which might explain the enhanced susceptibility. Limiting starch synthesis and enhancing fluxes towards redox and specialized metabolism also contributed to defence independent of N supply.

Phenylalanine treatment induces tomato resistance to Tuta absoluta via increased accumulation of benzenoid/phenylpropanoid volatiles serving as defense signals

Tuta absoluta ("leafminer"), is a major pest of tomato crops worldwide. Controlling this insect is difficult due to its efficient infestation, rapid proliferation, and resilience to changing weather conditions. Furthermore, chemical pesticides have only a short-term effect due to rapid development of T. absoluta strains. Here, we show that a variety of tomato cultivars, treated with external phenylalanine solutions exhibit high resistance to T. absoluta, under both greenhouse and open field conditions, at different locations. A large-scale metabolomic study revealed that tomato leaves absorb and metabolize externally given Phe efficiently, resulting in a change in their volatile profile, and repellence of T. absoluta moths. The change in the volatile profile is due to an increase in three phenylalanine-derived benzenoid phenylpropanoid volatiles (BPVs), benzaldehyde, phenylacetaldehyde, and 2-phenylethanol. This treatment had no effect on terpenes and green leaf volatiles, known to contribute to the fight against insects. Phe-treated plants also increased the resistance of neighboring non-treated plants. RNAseq analysis of the neighboring non-treated plants revealed an exclusive upregulation of genes, with enrichment of genes related to the plant immune response system. Exposure of tomato plants to either benzaldehyde, phenylacetaldehyde, or 2-phenylethanol, resulted in induction of genes related to the plant immune system that were also induced due to neighboring Phe-treated plants. We suggest a novel role of phenylalanine-derived BPVs as mediators of plant-insect interactions, acting as inducers of the plant defense mechanisms.

Germinating rice seeds shape rhizospheric bacteria via releasing benzaldehyde

Plants are not passively exposed to microbes during their life cycles, but rather shape the microbiome in their own way. However, little information is available about when and how plants recruit their microbes in the life cycles. We scrutinized the recruitment of soil microbes by rice (Oryza sativa) at the seed germination stage. Bacteria of Enterobacteria and Weeksellaceae were the most preferentially recruited by the germinating seeds, despite of many other bacteria in the soil. The seedlings that recruited Enterobacteria and Weeksellaceae bacteria notably outperformed those without these microbes in leaf length (by 54.21%), root length (by 188.11%) and biomass (by 88.65%). Further, we detected benzaldehyde, a plant-specific volatile metabolite, in the exudates of germinating seeds. Addition of benzaldehyde to the soil resulted in enrichment of Enterobacteria bacteria, suggesting that seed-released benzaldehyde could be a cue to recruit beneficial bacteria. Taken together, our results demonstrated that plants could recruit beneficial bacteria from the soil at the very early life stage of seed germination via releasing specific metabolites.

Phenylalanine in motion: A tale of an essential molecule with many faces

Phenylalanine has a unique role in plants as a source of a wide range of specialized metabolites, named phenylpropanoids that contribute to the adjustment of plants to changing developmental and environmental conditions. The profile of these metabolites differs between plants and plant organs. Some of the prominent phenylpropanoids include anthocyanins, phenolic acids, flavonoids, tannins, stilbenes, lignins, glucosinolates and benzenoid phenylpropanoid volatiles. Phenylalanine biosynthesis, leading to increased phenylpropanoid levels, is induced under stress. However, high availability of phenylalanine in plants under non-stressed conditions can be achieved either by genetically engineering plants to overproduce phenylalanine, or by external treatment of whole plants or detached plant organs with phenylalanine solutions. The objective of this review is to portray the many effects that increased phenylalanine availability has in plants under non-stressed conditions, focusing mainly on external applications. These applications include spraying and drenching whole plants with phenylalanine solutions, postharvest treatments by dipping fruit and cut flower stems, and addition of phenylalanine to cell suspensions. The results of these treatments include increased fragrance in flowers, increased aroma and pigmentation in fruit, increased production of health promoting metabolites in plant cell cultures, and increased resistance of plants, pre- and post-harvest, to a wide variety of pathogens. These effects suggest that plants can very efficiently uptake phenylalanine from their roots, leaves, flowers and fruits, translocate it from one organ to the other and between cell compartments, and metabolize it into phenylpropanoids. The mechanisms by which Phe treatment increases plant resistance to pathogens reveal new roles of phenylpropanoids in induction of genes related to the plant immune system. The simplicity of treatments with phenylalanine open many possibilities for industrial use. Many of the phenylalanine-treatment effects on increased resistance to plant pathogens have also been successful in commercial field trials.

Jasmonate signaling drives defense responses against Alternaria alternata in chrysanthemum

BACKGROUND

Black spot disease caused by the necrotrophic fungus Alternaria spp. is one of the most devastating diseases affecting Chrysanthemum morifolium. There is currently no effective way to prevent chrysanthemum black spot.

RESULTS

We revealed that pre-treatment of chrysanthemum leaves with the methy jasmonate (MeJA) significantly reduces their susceptibility to Alternaria alternata. To understand how MeJA treatment induces resistance, we monitored the dynamics of metabolites and the transcriptome in leaves after MeJA treatment following A. alternata infection. JA signaling affected the resistance of plants to pathogens through cell wall modification, Ca2+ regulation, reactive oxygen species (ROS) regulation, mitogen-activated protein kinase cascade and hormonal signaling processes, and the accumulation of anti-fungal and anti-oxidant metabolites. Furthermore, the expression of genes associated with these functions was verified by reverse transcription quantitative PCR and transgenic assays.

CONCLUSION

Our findings indicate that MeJA pre-treatment could be a potential orchestrator of a broad-spectrum defense response that may help establish an ecologically friendly pest control strategy and offer a promising way of priming plants to induce defense responses against A. alternata.

Investigating the Resistance Mechanism of Wheat Varieties to Fusarium Head Blight Using Comparative Metabolomics

Fusarium head blight (FHB) is primarily caused by Fusarium graminearum and severely reduces wheat yield, causing mycotoxin contamination in grains and derived products. F. graminearum-secreted chemical toxins stably accumulate in plant cells, disturbing host metabolic homeostasis. We determined the potential mechanisms underlying FHB resistance and susceptibility in wheat. Three representative wheat varieties (Sumai 3, Yangmai 158, and Annong 8455) were inoculated with F. graminearum and their metabolite changes were assessed and compared. In total, 365 differentiated metabolites were successfully identified. Amino acids and derivatives, carbohydrates, flavonoids, hydroxycinnamate derivatives, lipids, and nucleotides constituted the major changes in response to fungal infection. Changes in defense-associated metabolites, such as flavonoids and hydroxycinnamate derivatives, were dynamic and differed among the varieties. Nucleotide and amino acid metabolism and the tricarboxylic acid cycle were more active in the highly and moderately resistant varieties than in the highly susceptible variety. We demonstrated that two plant-derived metabolites, phenylalanine and malate, significantly suppressed F. graminearum growth. The genes encoding the biosynthetic enzymes for these two metabolites were upregulated in wheat spike during F. graminearum infection. Thus, our findings uncovered the metabolic basis of resistance and susceptibility of wheat to F. graminearum and provided insights into engineering metabolic pathways to enhance FHB resistance in wheat.

Genome-wide identification and validation of tomato-encoded sRNA as the cross-species antifungal factors targeting the virulence genes of Botrytis cinerea

Recent evidence shows that small RNAs are transferred from a species to another through cross-species transmission and exhibit biological activities in the receptor. In this study, we focused on tomato-derived sRNAs play a role of defense against Botrytis cinerea. Bioinformatics method was firstly employed to identify tomato-encoded sRNAs as the cross-species antifungal factors targeting B. cinerea genes. Then the expression levels of some identifed sRNAs were checked in B. cinerea-infected plant using qRT-PCR method. Exogenic RNA-induced gene silences analysis were performed to investigate the antifungal roles of the sRNAs, and the target genes in B. cinerea of antifungal sRNAs would be confirmed by using co-expression analysis. Results showed that a total of 21 B.cinerea-induced sRNAs with high abundance were identified as the cross-kingdom regulator candidates. Among them, three sRNAs containing a miRNA (miR396a-5p) and two siRNA (siR3 and siR14) were selected for experimental validation and bioassay analysis. qRT-PCR confirmed that all of these 3 sRNAs were induced in tomato leaves by B. cinerea infection. Correspondingly, 4 virulence genes of B. cinerea respectively targeted by these 3 sRNAs were down-regulated. Bioassay revealed that all of these 3 cross-species sRNAs could inhibit the virulence and spore gemination of B. cinerea. Correspondingly, the coding genes of B. cinerea targeted by these sRNAs were also down-regulated. Moreover, the virulence inhibition by double strand sRNA was more effective than that by single strand sRNA. The inhibition efficiency of sRNA against B. cinerea increased with the increase of its concentration. Our findings provide new evidence into the coevolution of pathogens and host plants, as well as new directions for the use of plant-derived sRNAs to control pathogens.

Untargeted 1 H-NMR Metabolome of Celery During Fusarium Wilt: Implications for Vegetable Quality

Celery is a vegetable widely consumed as a condiment to prepare diverse dishes around the world. Nevertheless, this plant is susceptible to the attack of several phytopathogens including those of the Fusarium genus which is translated into devastating losses for the production chain. Herein we report on the metabolic changes produced during the celery wilt caused by Fusarium oxysporum which was determined through untargeted ¹ H-NMR metabolomics. The changes in the metabolite content of celery were measured at 16, 24, and 32 days post-inoculation using viable conidia obtained from the native F. oxysporum strain FO3. Our results demonstrated that the parasitic activity of the fungus reduced the endogenous levels of free sugars (fructose, galactose, glucose isomers, mannose, Myo-inositol, mannitol, and sucrose) amino acids (alanine, aspartate GABA, glutamate, glutamine, histidine, isoleucine, leucine, methionine, proline, threonine, tyrosine, and valine), nucleosides (adenosine, cytidine, guanosine, and uridine) and organic acids (citric acid, fumaric acid, malic acid, and succinic acid). Interestingly, the levels of tyrosine and tryptophan were triggered as a consequence of F. oxysporum infection. This tendency was correlated with an increase in the levels of chlorogenic acid, apiin, and apigenin derivatives, suggesting their involvement in the chemical defense of celery against fungal colonization. According to principal component analysis (PCA) and Orthogonal Projections to Latent Structures Discriminant Analysis (OPLS-DA) methanol was the main differential metabolite and it was considered as a new chemical marker associated with F. oxysporum infection. Our results demonstrate that infected celery plants dramatically reduced their nutritional and nutraceutical contents during Fusarium wilt after 32 days post-inoculation. However, these findings also suggest that the phenylpropanoid pathway is strongly related with the chemical defense of celery against F. oxysporum.

Fusarium oxysporum infection on root elicit aboveground terpene production and salicylic acid accumulation in Chrysanthemum morifolium

Underground infection of Fusarium oxysporum resulted in great yield losses in chrysanthemum (Chrysanthemum morifolium Ramat.) industry. However, the effect of F. oxysporum root disease on the terpenes production in above- and below-ground parts of plant is completely unexplored. The aim of this study was to investigate the systematic impact of Fusarium infection underground on the terpene production in aboveground parts of chrysanthemum. Terpene production in above- and below-ground parts was profiled in a time series of post-inoculation by GC-MS. Total terpenes were significantly induced from roots and leaves of Fusarium-infected versus healthy plants. These terpenes included monoterpenes, sesquiterpenes and diterpenes, in which sesquiterpenes were primarily induced in roots and leaves, while monoterpenes were produced only in leaves. Through transcriptome analysis, 8 differentially expressed terpene synthase genes (TPSs) were screened out. The relative expression levels of 8 TPS genes at different developmental stage and tissues indicated the spatial delay of the TPS genes in leaves. The induced terpenes from roots and leaves showed consistency with the expression pattern of TPS genes. The biochemical function of Cm-j-TPS1/2/7 were verified by enzymatic assay. Additionally, it's found that the content of salicylic acid (SA) in root and leaf significantly increased by F. oxysporum infection, suggesting a role of the SA signaling pathway in defense. Together, these results reveal the defense response of above- and below-ground parts of plants to root fungal attack and provide a theoretical basis for the effective prediction and control of F. oxysporum infection in chrysanthemum.

Preharvest Application of Phenylalanine Induces Red Color in Mango and Apple Fruit’s Skin

Anthocyanins are secondary metabolites responsible for the red coloration of mango and apple. The red color of the peel is essential for the fruit’s marketability. Anthocyanins and flavonols are synthesized via the flavonoid pathway initiated from phenylalanine (Phe). Anthocyanins and flavonols have antioxidant, antifungal, and health-promoting properties. To determine if the external treatment of apple and mango trees with Phe can induce the red color of the fruit peel, the orchards were sprayed 1 to 4 weeks before the harvest of mango (cv. Kent, Shelly, and Tommy Atkins) and apple fruit (cv. Cripps pink, Gala and Starking Delicious). Preharvest Phe treatment increased the red coloring intensity and red surface area of both mango and apple fruit that was exposed to sunlight at the orchard. The best application of Phe was 2–4 weeks preharvest at a concentration of 0.12%, while a higher concentration did not have an additive effect. A combination of Phe and the positive control of prohydrojasmon (PDJ) or several applications of Phe did not have a significant added value on the increase in red color. Phe treatment increased total flavonoid, anthocyanin contents, and antioxidant activity in treated fruit compared to control fruits. High Performance Liquid Chromatography analysis of the peel of Phe treated ‘Cripps pink’ apples showed an increase in total flavonols and anthocyanins with no effect on the compound composition. HPLC analysis of ‘Kent’ mango fruit peel showed that Phe treatment had almost no effect on total flavonols content while significantly increasing the level of anthocyanins was observed. Thus preharvest application of Phe combined with sunlight exposure offers an eco–friendly, alternative treatment to improve one of the most essential quality traits—fruit color.

Double-stranded RNA targeting fungal ergosterol biosynthesis pathway controls Botrytis cinerea and postharvest grey mould

Pathogenic fungi cause major postharvest losses. During storage and ripening, fruit becomes highly susceptible to fungi that cause postharvest disease. Fungicides are effective treatments to limit disease. However, due to increased public concern for their possible side effects, there is a need to develop new strategies to control postharvest fungal pathogens. Botrytis cinerea, a common postharvest pathogen, was shown to uptake small double-stranded RNA (dsRNA) molecules from the host plant. Such dsRNA can regulate gene expression through the RNA interference system. This work aimed to develop a synthetic dsRNA simultaneously targeting three essential transcripts active in the fungal ergosterol biosynthesis pathway (dsRNA-ERG). Our results show initial uptake of dsRNA in the emergence zone of the germination tube that spreads throughout the fungus and results in down-regulation of all three targeted transcripts. Application of dsRNA-ERG decreased B. cinerea germination and growth in in vitro conditions and various fruits, leading to reduce grey-mould decay. The inhibition of growth or decay was reversed by the addition of ergosterol. While dual treatment with dsRNA-ERG and ergosterol-inhibitor fungicide reduced by 100-fold the required amount of fungicide to achieve the same protection rate. The application of dsRNA-ERG induced systemic protection as shown by decreased decay development at inoculation points distant from the treatment point in tomato and pepper fruits. Overall, this study suggests that dsRNA-ERG can effectively control B. cinerea growth and grey-mould development suggesting its efficacy as a future method for postharvest control of fungal pathogens.

Protective Properties of the Extract of Chrysanthemum on Patients with Ischemic Stroke

Investigation of the protective effect of chrysanthemum extract in ischemic strokes patients is among the challenging issues with the traditional hospital system in general and smart technology-based hospitals in particular. In this study, we have evaluated the protective effect of chrysanthemum extract on patients with ischemic stroke by detecting the severity of stroke, neuronal indexes, and oxidative stress biomarkers. For this purpose, forty-six patients with ischemic stroke were randomly divided into the control group (n = 30) and chrysanthemum group (n = 30). The control group received standard stroke treatment, and the chrysanthemum group was treated with chrysanthemum extract 400 mg/day (200 mg/day, twice/day) on the basis of standard treatment. The groups were compared the effect of saffron capsules using the National Institute of Health Stoke Scale (NIHSS), serum neuron specific enolase (NSE), S100, brain-derived neurotrophic factor (BDNF), malondialdehyde (MDA), Su-peroxide dismutase (SOD), and total antioxidant capacity (TAC ) levels, at the time of first day and fourth day after treatment. On the first day after treatment, there was no significant difference in the NIHSS score, serum NSE, S100, BDNF, MDA, SOD, and TAC levels between the chrysanthemum group and the control group (P > 0.05). On the fourth day after treatment, the NIHSS, serum NSE, S100, and MDA levels were significantly reduced in the chrysanthemum group compared to the control group, while the BDNF, SOD, and TAC levels were higher (P < 0.05). In addition, compared to the levels on the first day, the NIHSS, serum NSE, S100, and MDA levels were significantly reduced, and the BDNF, SOD, and TAC levels were increased in the chrysanthemum group on the fourth day (P < 0.05). Chrysanthemum extract has the effects of scavenging oxygen free radicals and antioxidation and has a neuroprotective effect on ischemic stroke patients.

PAL1 gene of the phenylpropanoid pathway increases resistance to the Cassava brown streak virus in cassava

BACKGROUND

The phenylalanine ammonia lyase genes play crucial role in plant response to biotic and abiotic stresses. In this study, we characterized the role of PAL genes in increasing resistance to the Cassava brown streak virus that causes the economically important cassava brown streak disease (CBSD) on cassava in Africa.

METHODS

The whole transcriptomes of eight cassava varieties differing in resistance to CBSD were obtained at 1, 5 and 8 weeks after CBSV infection.

RESULTS

Analysis of RNA-Seq data identified the overexpression of PAL1, PAL2, cinnamic acid and two chalcone synthase genes in CBSD-resistant cassava varieties, which was subsequently confirmed by RT-qPCR. The exogenous application of Acibenzolar-S-Methyl induced PAL1 gene expression to enhance resistance in the susceptible var. Kalawe. In contrast, the silencing of PAL1 by RNA interference led to increased susceptibility of the resistant var. Kaleso to CBSD.

CONCLUSIONS

PAL1 gene of the phenylpropanoid pathway has a major role in inducing resistance to CBSD in cassava plants and its early induction is key for CBSD resistance.

Spermine and Spermidine Priming against Botrytis cinerea Modulates ROS Dynamics and Metabolism in Arabidopsis

Polyamines (PAs) are ubiquitous small aliphatic polycations important for growth, development, and environmental stress responses in plants. Here, we demonstrate that exogenous application of spermine (Spm) and spermidine (Spd) induced cell death at high concentrations, but primed resistance against the necrotrophic fungus Botrytis cinerea in Arabidopsis. At low concentrations, Spm was more effective than Spd. Treatments with higher exogenous Spd and Spm concentrations resulted in a biphasic endogenous PA accumulation. Exogenous Spm induced the accumulation of H2O2 after treatment but also after infection with B. cinerea. Both Spm and Spd induced the activities of catalase, ascorbate peroxidase, and guaiacol peroxidase after treatment but also after infection with B. cinerea. The soluble sugars glucose, fructose, and sucrose accumulated after treatment with high concentrations of PAs, whereas only Spm induced sugar accumulation after infection. Total and active nitrate reductase (NR) activities were inhibited by Spm treatment, whereas Spd inhibited active NR at low concentrations but promoted active NR at high concentrations. Finally, γaminobutyric acid accumulated after treatment and infection in plants treated with high concentrations of Spm. Phenylalanine and asparagine also accumulated after infection in plants treated with a high concentration of Spm. Our data illustrate that Spm and Spd are effective in priming resistance against B. cinerea, opening the door for the development of sustainable alternatives for chemical pesticides.

Metabolic and Transcriptomic Profiling of Lilium Leaves Infected With Botrytis elliptica Reveals Different Stages of Plant Defense Mechanisms

Botrytis elliptica, the causal agent of gray mold disease, poses a major threat to commercial Lilium production, limiting its ornamental value and yield. The molecular and metabolic regulation mechanisms of Lilium's defense response to B. elliptica infection have not been completely elucidated. Here, we performed transcriptomic and metabolomic analyses of B. elliptica resistant Lilium oriental hybrid "Sorbonne" to understand the molecular basis of gray mold disease resistance in gray mold disease. A total of 115 differentially accumulated metabolites (DAMs) were detected by comparing the different temporal stages of pathogen infection. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed the differentially expressed genes (DEGs) and DAMs were enriched in the phenylpropanoid and flavonoid pathways at all stages of infection, demonstrating the prominence of these pathways in the defense response of "Sorbonne" to B. elliptica. Network analysis revealed high interconnectivity of the induced defense response. Furthermore, time-course analysis of the transcriptome and a weighted gene coexpression network analysis (WGCNA) led to the identification of a number of hub genes at different stages, revealing that jasmonic acid (JA), salicylic acid (SA), brassinolide (BR), and calcium ions (Ca²⁺) play a crucial role in the response of "Sorbonne" to fungal infection. Our work provides a comprehensive perspective on the defense response of Lilium to B. elliptica infection, along with a potential transcriptional regulatory network underlying the defense response, thereby offering gene candidates for resistance breeding and metabolic engineering of Lilium.