The Biosynthetic Pathway of Indole-3-Carbaldehyde and Indole-3-Carboxylic Acid Derivatives in Arabidopsis

Deciphering the therapeutic potential of SheXiangXinTongNing: Interplay between gut microbiota and brain metabolomics in a CUMS mice model, with a focus on tryptophan metabolism

Depression, a prevalent and multifaceted mental disorder, has emerged as a significant public health concern due to its escalating prevalence and heightened risk of severe suicidality. Given its profound impact, the imperative for preventing and intervening in depression is paramount. Substantial evidence underscores intricate connections between depression and cardiovascular health. SheXiangXinTongNing (XTN), a recognized traditional Chinese medicine for treating Coronary Heart Disease (CHD), prompted our exploration into its antidepressant effects and underlying mechanisms. In this investigation, we assessed XTN's antidepressant potential using the chronic unpredictable mild stress (CUMS) mice model and behavioral tests. Employing network pharmacology, we delved into the intricate mechanisms at play. We characterized the microbial composition and function in CUMS mice, both with and without XTN treatment, utilizing 16S rRNA sequencing and metabolomics analysis. The joint analysis of these results via Cytoscape identified pivotal metabolic pathways. In the realm of network pharmacology, XTN administration exhibited antidepressant effects by modulating pathways such as IL-17, neuroactive ligand-receptor interaction, PI3K-Akt, cAMP, calcium, and dopamine synapse signaling pathways. Our findings revealed that XTN significantly mitigated depression-like symptoms and cognitive deficits in CUMS mice by inhibiting neuroinflammation and pyroptosis. Furthermore, 16S rRNA sequencing unveiled that XTN increased the alpha-diversity and beta-diversity of the gut microbiome in CUMS mice. Metabolomics analysis identified brain metabolites crucial for distinguishing between the CUMS and CUMS+XTN groups, with a focus on pathways like Tryptophan metabolism and Linoleic acid metabolism. Notably, specific bacterial families, including Alloprevotella, Helicobacter, Allobaculum, and Clostridia, exhibited robust co-occurring relationships with brain tryptophan metabolomics, hinting at the potential mediating role of gut microbiome alterations and metabolites in the efficacy of XTN treatment. In conclusion, our study unveils modifications in microbial compositions and metabolic functions may be pivotal in understanding the response to XTN treatment, offering novel insights into the mechanisms underpinning the efficacy of antidepressants.

Cardiac glycosides protect wormseed wallflower (Erysimum cheiranthoides) against some, but not all, glucosinolate-adapted herbivores

The chemical arms race between plants and insects is foundational to the generation and maintenance of biological diversity. We asked how the evolution of a novel defensive compound in an already well-defended plant lineage impacts interactions with diverse herbivores. Erysimum cheiranthoides (Brassicaceae), which produces both ancestral glucosinolates and novel cardiac glycosides, served as a model. We analyzed gene expression to identify cardiac glycoside biosynthetic enzymes in E. cheiranthoides and characterized these enzymes via heterologous expression and CRISPR/Cas9 knockout. Using E. cheiranthoides cardiac glycoside-deficient lines, we conducted insect experiments in both the laboratory and field. EcCYP87A126 initiates cardiac glycoside biosynthesis via sterol side-chain cleavage, and EcCYP716A418 has a role in cardiac glycoside hydroxylation. In EcCYP87A126 knockout lines, cardiac glycoside production was eliminated. Laboratory experiments with these lines revealed that cardiac glycosides were highly effective defenses against two species of glucosinolate-tolerant specialist herbivores, but did not protect against all crucifer-feeding specialist herbivores in the field. Cardiac glycosides had lesser to no effect on two broad generalist herbivores. These results begin elucidation of the E. cheiranthoides cardiac glycoside biosynthetic pathway and demonstrate in vivo that cardiac glycoside production allows Erysimum to escape from some, but not all, specialist herbivores.

Overexpressing CYP81D11 enhances 2,4,6-trinitrotoluene tolerance and removal efficiency in Arabidopsis

Phytoremediation is a promising technology for removing the high-toxic explosive 2,4,6-trinitrotoluene (TNT) pollutant from the environment. Mining dominant genes is the key research direction of this technology. Most previous studies have focused on the detoxification of TNT rather than plants' TNT tolerance. Here, we conducted a transcriptomic analysis of wild type Arabidopsis plants under TNT stress and found that the Arabidopsis cytochrome P450 gene CYP81D11 was significantly induced in TNT-treated plants. Under TNT stress, the root length was approximately 1.4 times longer in CYP81D11-overexpressing transgenic plants than in wild type plants. The half-removal time for TNT was much shorter in CYP81D11-overexpressing transgenic plants (1.1 days) than in wild type plants (t1/2 = 2.2 day). In addition, metabolic analysis showed no difference in metabolites in transgenic plants compared to wild type plants. These results suggest that the high TNT uptake rates of CYP81D11-overexpressing transgenic plants were most likely due to increased tolerance and biomass rather than TNT degradation. However, CYP81D11-overexpressing plants were not more tolerant to osmotic stresses, such as salt or drought. Taken together, our results indicate that CYP81D11 is a promising target for producing bioengineered plants with high TNT removing capability.

Investigation into the role of carboxylic acid and phenolic hydroxyl groups in the plant biostimulant activity of a humic acid purified from an oxidized sub-bituminous coal

Introduction

Humic substances (HS) are increasingly being applied as crop plant biostimulants because they have been shown to increase plant productivity, especially under environmentally stressful conditions. There has been intense interest in elucidating the HS molecular structures responsible for eliciting the plant biostimulant response (PBR). The polar and weakly acidic carboxylic (COOH) and phenolic hydroxyl (ArOH) functional groups play major roles in the acid nature, pH dependent solubilities, conformation, and metal- and salt-binding capabilities of HS. Reports on the role played by these groups in the PBR of HS found growth parameters being both positively and negatively correlated with COOH and ArOH functionalities.

Materials and methods

To investigate the role of COOH and ArOH in HS biostimulant activity we used a humic acid (HA), purified from an oxidized sub bituminous coal to prepare HAs with COOH groups methylated (AHA), ArOH groups acetylated (OHA), and with both COOH and ArOH groups methylated (FHA). The original HA was designated (NHA). The four HAs were subjected to elemental, 13C-NMR, FTIR, and EPR analyses and their antioxidant properties were assessed using the trolox equivalents antioxidant capacity assay (TEAC). 13C-NMR and FTIR analysis revealed significant alkylation/acetylation. To determine the effects of alkylating/acetylating these functional groups on the HA elicited PBR, the HAs were evaluated in a plant bioassay on corn (Zea mays L.) seedling under nutrient and non-nutrient stressed conditions. Treatments consisted of the four HAs applied to the soil surface at a concentration of 80 mg C L-1, in 50 ml DI H2O with the control plants receiving 50ml DI H2O.

Results

The HA-treated plants, at both fertilization rates, were almost always significantly larger than their respective control plants. However, the differences produced under nutrient stress were always much greater than those produced under nutrient sufficiency, supporting previous reports that HA can reduce the effects of stress on plant growth. In addition, for the most part, the HAs with the alkylated/acetylated groups produced plants equal to or larger than plants treated with NHA.

Conclusion

These results suggests that COOH and ArOH groups play a limited or no role in the HA elicited PBR. Alternatively, the HA pro-oxidant to antioxidant ratio may play a role in the magnitude of the biostimulant response.

Pseudomonas syringae infectivity correlates to altered transcript and metabolite levels of Arabidopsis mediator mutants

Rapid metabolic responses to pathogens are essential for plant survival and depend on numerous transcription factors. Mediator is the major transcriptional co-regulator for integration and transmission of signals from transcriptional regulators to RNA polymerase II. Using four Arabidopsis Mediator mutants, med16, med18, med25 and cdk8, we studied how differences in regulation of their transcript and metabolite levels correlate to their responses to Pseudomonas syringae infection. We found that med16 and cdk8 were susceptible, while med25 showed increased resistance. Glucosinolate, phytoalexin and carbohydrate levels were reduced already before infection in med16 and cdk8, but increased in med25, which also displayed increased benzenoids levels. Early after infection, wild type plants showed reduced glucosinolate and nucleoside levels, but increases in amino acids, benzenoids, oxylipins and the phytoalexin camalexin. The Mediator mutants showed altered levels of these metabolites and in regulation of genes encoding key enzymes for their metabolism. At later stage, mutants displayed defective levels of specific amino acids, carbohydrates, lipids and jasmonates which correlated to their infection response phenotypes. Our results reveal that MED16, MED25 and CDK8 are required for a proper, coordinated transcriptional response of genes which encode enzymes involved in important metabolic pathways for Arabidopsis responses to Pseudomonas syringae infections.

Exploring the Interaction of Indole-3-Acetonitrile with Neuroblastoma Cells: Understanding the Connection with the Serotonin and Dopamine Pathways

Indole-3-acetonitrile, a compound produced by bacteria and plants as a defense and survival signal in response to attacks, has been recently discovered as a metabolite produced by human cancer cells. This discovery suggests a potential association between IAN and cancer progression in patients. Consequently, the aim of this work was to study the effects of IAN on a specific cancer cell line, SH-SY5Y, and elucidate its connection to the serotonin and dopamine pathways by examining the precursors of these neurotransmitters. To achieve this, a cellular viability assay was conducted, along with a morphological evaluation of the cells under both normal and stress conditions. Our results demonstrated that for the highest concentrations in our study, IAN was able to reduce the cellular viability of the cells. Furthermore, when IAN was combined with the amino acids that originate the neurotransmitters, it was possible to observe that in both combinations there was a decrease in the viability of the cells. Thus, IAN may in fact have some influence on both the serotonin and dopamine pathways since changes in cell viability were observed when it was added together with the amino acids. This preliminary study indicates the presence of an interaction between IAN and neuroblastoma cells that justifies further exploration and study.

Hormonal and proteomic analyses of southern blight disease caused by Athelia rolfsii and root chitosan priming on Cannabis sativa in an in vitro hydroponic system

Southern blight disease, caused by the fungal pathogen Athelia rolfsii, suppresses plant growth and reduces product yield in Cannabis sativa agriculture. Mechanisms of pathology of this soil-borne disease remain poorly understood, with disease management strategies reliant upon broad-spectrum antifungal use. Exposure to chitosan, a natural elicitor, has been proposed as an alternative method to control diverse fungal diseases in an eco-friendly manner. In this study, C. sativa plants were grown in the Root-TRAPR system, a transparent hydroponic growth device, where plant roots were primed with .2% colloidal chitosan prior to A. rolfsii inoculation. Both chitosan-primed and unprimed inoculated plants displayed classical symptoms of wilting and yellowish leaves, indicating successful infection. Non-primed infected plants showed increased shoot defense responses with doubling of peroxidase and chitinase activities. The levels of growth and defense hormones including auxin, cytokinin, and jasmonic acid were increased 2-5-fold. In chitosan-primed infected plants, shoot peroxidase activity and phytohormone levels were decreased 1.5-4-fold relative to the unprimed infected plants. When compared with shoots, roots were less impacted by A. rolfsii infection, but the pathogen secreted cell wall-degrading enzymes into the root-growth solution. Chitosan priming inhibited root growth, with root lengths of chitosan-primed plants approximately 65% shorter than the control, but activated root defense responses, with root peroxidase activity increased 2.7-fold along with increased secretion of defense proteins. The results suggest that chitosan could be an alternative platform to manage southern blight disease in C. sativa cultivation; however, further optimization is required to maximize effectiveness of chitosan.

Priestia megaterium Metabolism: Isolation, Identification of Naringenin Analogues and Genes Elevated Associated with Nanoparticle Intervention

The impact of gold nanoparticles (AuNPs) on the biosynthetic manipulation of Priestia megaterium metabolism where an existing gene cluster is enhanced to produce and enrich bioactive secondary metabolites has been studied previously. In this research, we aimed to isolate and elucidate the structure of metabolites of compounds 1 and 2 which have been analyzed previously in P. megaterium crude extract. This was achieved through a PREP-ODS C18 column with an HPLC-UV/visible detector. Then, the compounds were subjected to nuclear magnetic resonance (NMR), electrospray ionization mass spectrometry (ESI-MS), and Fourier-transform infrared spectroscopy (FT-IR) techniques. Furthermore, bioinformatics and transcriptome analysis were used to examine the gene expression for which the secondary metabolites produced in the presence of AuNPs showed significant enhancement in transcriptomic responses. The metabolites of compounds 1 and 2 were identified as daidzein and genistein, respectively. The real-time polymerase chain reaction (RT-PCR) technique was used to assess the expression of three genes (csoR, CHS, and yjiB) from a panel of selected genes known to be involved in the biosynthesis of the identified secondary metabolites. The expression levels of two genes (csoR and yijB) increased in response to AuNP intervention, whereas CHS was unaffected.

Oxidative rearrangement of tryptophan to indole nitrile by a single diiron enzyme

Nitriles are uncommon in nature and are typically constructed from oximes via the oxidative decarboxylation of amino acid substrates or from the derivatization of carboxylic acids. Here we report a third strategy of nitrile biosynthesis featuring the cyanobacterial nitrile synthase AetD. During the biosynthesis of the 'eagle-killing' neurotoxin, aetokthonotoxin, AetD converts the alanyl side chain of 5,7-dibromo-L-tryptophan to a nitrile. Employing a combination of structural, biochemical, and biophysical techniques, we characterized AetD as a non-heme diiron enzyme that belongs to the emerging Heme Oxygenase-like Diiron Oxidase and Oxygenase (HDO) superfamily. High-resolution crystal structures of AetD together with the identification of catalytically relevant products provide mechanistic insights into how AetD affords this unique transformation that we propose proceeds via an aziridine intermediate. Our work presents a new paradigm for nitrile biogenesis and portrays a substrate binding and metallocofactor assembly mechanism that may be shared among other HDO enzymes.

Chemical compositions of Souliea vaginata (Maxim) Franch rhizome and their potential therapeutic effects on collagen-induced arthritis in rats

ETHNOPHARMACOLOGICAL REVEVANCE

Rheumatoid arthritis (RA) is a global prevalent chronic autoimmune inflammatory disease and acceptable safety drugs are lack for its treatment. The rhizomes of Souliea vaginata (Maxim) Franch (SV) possess anti-inflammatory functions and are used as substitution of Coptis chinensis Franch. SV is also traditional Chinese medicine and Tibetan medicine for the treatment of conjunctivitis, enteritis and rheumatic. For searching complementary and alternative anti-RA drugs, it is necessary to characterize the potential anti-arthritic activity of SV and underlying mechanism involved.

AIM OF THE STUDY

The aim of the study was to test the chemical compositions, evaluate the anti-arthritic effects and underlying mechanisms of SV.

MATERIALS AND METHODS

The chemical compositions of SV were analyzed using liquid chromatography-ion trap-time of flight tandem mass spectrometry (LCMS-IT-TOF). From day 11 to day 31, SV (0.5, 1.0 and 1.5 g/kg body weight) and Tripterygium glycosidorum (TG, 10 mg/kg body weight) were administered orally to the CIA model rats once a day. Thickness of paw and body weights were measured once every two days from day 1 to day 31. Histopathological changes were measured using hematoxylin-eosin (HE) staining. Effects of SV on the levels of IL-2, TNF-α, IFN-γ, IL-4 and IL-10 in serum of CIA rats were measured by enzyme-linked immunosorbent assay (ELISA) kits. CD3⁺, CD4⁺, CD8⁺ and CD4⁺CD25⁺ T cells populations were measured using flow cytometric analysis. To evaluate the possible hepatotoxicity and nephrotoxicity, the serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), blood urea (UREA) and creatinine (CREA) in CIA rats were also tested using blood auto analyzer.

RESULTS

34 compounds were identified from SV based on LCMS-IT-TOF, and triterpenoids are major anti-arthritic compositions. SV significantly relieved CIA rats' paw swelling without obvious influence on the body weight growth. SV decreased the serum levels of IL-2, TNF-α and IFN-γ in CIA rat, and increased the serum levels of IL-4 and IL-10. SV significantly increased and decreased the percentages of CD4⁺ and CD8⁺, with no significant effects on CD3⁺ in lymphocytes of CIA model rats. Moreover, SV simultaneously decreased thymus and spleen indexes and no hepatotoxicity and nephrotoxicity was observed after short-term treatment.

CONCLUSION

These findings suggest that SV possesses preventive and therapeutic effect on RA by modulating the inflammatory cytokines, T-lymphocyte, thymus and spleen indexes and shows no hepatotoxicity and nephrotoxicity.

Loss of Chloroplast GNAT Acetyltransferases Results in Distinct Metabolic Phenotypes in Arabidopsis

Acetylation is one of the most common chemical modifications found on a variety of molecules ranging from metabolites to proteins. Although numerous chloroplast proteins have been shown to be acetylated, the role of acetylation in the regulation of chloroplast functions has remained mainly enigmatic. The chloroplast acetylation machinery in Arabidopsis thaliana consists of eight General control non-repressible 5 (GCN5)-related N-acetyltransferase (GNAT)-family enzymes that catalyze both N-terminal and lysine acetylation of proteins. Additionally, two plastid GNATs have also been reported to be involved in the biosynthesis of melatonin. Here, we have characterized six plastid GNATs (GNAT1, GNAT2, GNAT4, GNAT6, GNAT7 and GNAT10) using a reverse genetics approach with an emphasis on the metabolomes and photosynthesis of the knock-out plants. Our results reveal the impact of GNAT enzymes on the accumulation of chloroplast-related compounds, such as oxylipins and ascorbate, and the GNAT enzymes also affect the accumulation of amino acids and their derivatives. Specifically, the amount of acetylated arginine and proline was significantly decreased in the gnat2 and gnat7 mutants, respectively, as compared to the wild-type Col-0 plants. Additionally, our results show that the loss of the GNAT enzymes results in increased accumulation of Rubisco and Rubisco activase (RCA) at the thylakoids. Nevertheless, the reallocation of Rubisco and RCA did not have consequent effects on carbon assimilation under the studied conditions. Taken together, our results show that chloroplast GNATs affect diverse aspects of plant metabolism and pave way for future research into the role of protein acetylation.

Untargeted Metabolomics of Alternaria solani-Challenged Wild Tomato Species Solanum cheesmaniae Revealed Key Metabolite Biomarkers and Insight into Altered Metabolic Pathways

Untargeted metabolomics of moderately resistant wild tomato species Solanum cheesmaniae revealed an altered metabolite profile in plant leaves in response to Alternaria solani pathogen. Leaf metabolites were significantly differentiated in non-stressed versus stressed plants. The samples were discriminated not only by the presence/absence of specific metabolites as distinguished markers of infection, but also on the basis of their relative abundance as important concluding factors. Annotation of metabolite features using the Arabidopsis thaliana (KEGG) database revealed 3371 compounds with KEGG identifiers belonging to biosynthetic pathways including secondary metabolites, cofactors, steroids, brassinosteroids, terpernoids, and fatty acids. Annotation using the Solanum lycopersicum database in PLANTCYC PMN revealed significantly upregulated (541) and downregulated (485) features distributed in metabolite classes that appeared to play a crucial role in defense, infection prevention, signaling, plant growth, and plant homeostasis to survive under stress conditions. The orthogonal partial least squares discriminant analysis (OPLS-DA), comprising a significant fold change (≥2.0) with VIP score (≥1.0), showed 34 upregulated biomarker metabolites including 5-phosphoribosylamine, kaur-16-en-18-oic acid, pantothenate, and O-acetyl-L-homoserine, along with 41 downregulated biomarkers. Downregulated metabolite biomarkers were mapped with pathways specifically known for plant defense, suggesting their prominent role in pathogen resistance. These results hold promise for identifying key biomarker metabolites that contribute to disease resistive metabolic traits/biosynthetic routes. This approach can assist in mQTL development for the stress breeding program in tomato against pathogen interactions.

Dopamine Inhibits Arabidopsis Growth through Increased Oxidative Stress and Auxin Activity

Like some bacterial species and all animals, plants synthesize dopamine and react to its exogenous applications. Despite dopamine’s widespread presence and activity in plants, its role in plant physiology is still poorly understood. Using targeted experimentation informed by the transcriptomic response to dopamine exposure, we identify three major effects of dopamine. First, we show that dopamine causes hypersensitivity to auxin indole-3-acetic acid by enhancing auxin activity. Second, we show that dopamine increases oxidative stress, which can be mitigated with glutathione. Third, we find that dopamine downregulates iron uptake mechanisms, leading to a decreased iron content—a response possibly aimed at reducing DA-induced oxidative stress. Finally, we show that dopamine-induced auxin sensitivity is downstream of glutathione biosynthesis, indicating that the auxin response is likely a consequence of DA-induced oxidative stress. Collectively, our results show that exogenous dopamine increases oxidative stress, which inhibits growth both directly and indirectly by promoting glutathione-biosynthesis-dependent auxin hypersensitivity.

Promiscuity, a Driver of Plant Cytochrome P450 Evolution?

Plant cytochrome P450 monooxygenases were long considered to be highly substrate-specific, regioselective and stereoselective enzymes, in this respect differing from their animal counterparts. The functional data that have recently accumulated clearly counter this initial dogma. Highly promiscuous P450 enzymes have now been reported, mainly in terpenoid pathways with functions in plant adaptation, but also some very versatile xenobiotic/herbicide metabolizers. An overlap and predictable interference between endogenous and herbicide metabolism are starting to emerge. Both substrate preference and permissiveness vary between plant P450 families, with high promiscuity seemingly favoring retention of gene duplicates and evolutionary blooms. Yet significant promiscuity can also be observed in the families under high negative selection and with essential functions, usually enhanced after gene duplication. The strategies so far implemented, to systematically explore P450 catalytic capacity, are described and discussed.

Optimization of the growth conditions through response surface methodology and metabolomics for maximizing the auxin production by Pantoea agglomerans C1

Introduction

The fermentative production of auxin/indole 3-acetate (IAA) using selected Pantoea agglomerans strains can be a promising approach to developing novel plant biostimulants for agriculture use.

Methods

By integrating metabolomics and fermentation technologies, this study aimed to define the optimal culture conditions to obtain auxin/IAA-enriched plant postbiotics using P. agglomerans strain C1. Metabolomics analysis allowed us to demonstrate that the production of a selected.

Results and discussion

Array of compounds with plant growth-promoting- (IAA and hypoxanthine) and biocontrol activity (NS-5, cyclohexanone, homo-L-arginine, methyl hexadecenoic acid, and indole-3-carbinol) can be stimulated by cultivating this strain on minimal saline medium amended with sucrose as a carbon source. We applied a three-level-two-factor central composite design (CCD) based response surface methodology (RSM) to explore the impact of the independent variables (rotation speed and medium liquid-to-flask volume ratio) on the production of IAA and IAA precursors. The ANOVA component of the CCD indicated that all the process-independent variables investigated significantly impacted the auxin/IAA production by P. agglomerans strain C1. The optimum values of variables were a rotation speed of 180 rpm and a medium liquid-to-flask volume ratio of 1:10. Using the CCD-RSM method, we obtained a maximum indole auxin production of 208.3 ± 0.4  mg IAA_equ/L, which was a 40% increase compared to the growth conditions used in previous studies. Targeted metabolomics allowed us to demonstrate that the IAA product selectivity and the accumulation of the IAA precursor indole-3-pyruvic acid were significantly affected by the increase in the rotation speed and the aeration efficiency.

Metabolite Profiling and Bioassay-Guided Fractionation of Zataria multiflora Boiss. Hydroethanolic Leaf Extracts for Identification of Broad-Spectrum Pre and Postharvest Antifungal Agents

Hydroethanolic leaf extracts of 14 Iranian Zataria multiflora Boiss. populations were screened for their antifungal activity against five plant pathogenic fungi and metabolically profiled using a non-targeted workflow based on UHPLC/ESI-QTOFMS. Detailed tandem mass-spectrometric analyses of one of the most active hydroethanolic leaf extracts led to the annotation of 68 non-volatile semi-polar secondary metabolites, including 33 flavonoids, 9 hydroxycinnamic acid derivatives, 14 terpenoids, and 12 other metabolites. Rank correlation analyses using the abundances of the annotated metabolites in crude leaf extracts and their antifungal activity revealed four O-methylated flavones, two flavanones, two dihydroflavonols, five thymohydroquinone glycoconjugates, and five putative phenolic diterpenoids as putative antifungal metabolites. After bioassay-guided fractionation, a number of mono-, di- and tri-O-methylated flavones, as well as three of unidentified phenolic diterpenoids, were found in the most active subfractions. These metabolites are promising candidates for the development of new natural fungicides for the protection of agro-food crops.

EuRBG10 involved in indole alkaloids biosynthesis in Eucommia ulmoides induced by drought and salt stresses

Alkaloids are natural products with many important medicinal activities. To explore the mechanism of abiotic stress promoting alkaloid biosynthesis in Eucommia ulmoides, transcriptomic analysis and metabonomic analysis were used, virus-induced gene silencing (VIGS) lines of target gene were constructed. The results showed that drought and salt stress caused wilting and blackening of leaves, decreased chlorophyll level, and significantly induced MDA and relative conductivity. To resist the damage of stress to cells, the level of secondary metabolites such as alkaloids increased significantly with the extension of stress time. Transcriptomic results showed that, were. Six alkaloid related genes (AWGs) were gathered in five modules positively correlated with either salt stress or alkaloid contents by WGCNA. Results of GO and KEGG enrichment revealed that biosynthesis of alkaloid, especially indole alkaloid was induced, and degradation of alkaloid was inhibited under salt stress. Combining the results of transcriptome and metabolomics, it was suggested that EuRBG10 promotes the production of indole alkaloids and EuAMO5 inhibits the degradation of alkaloids, which may be the core mechanism of the indole alkaloid biosynthesis pathway (map00901) induced by salt stress. The results of these hub proteins were also consistent with the chordal graph of KEGG enrichment. Hub roles of EuRGB10 was checked in E. ulmoides by VIGS. Our findings provide a preliminary understanding of abiotic stress regulating secondary metabolites such as alkaloids, and propose hub genes that can be used to improve the level of bioactive components in medicinal plant.

Alternative splicing of Arabidopsis G6PD5 recruits NADPH-producing OPPP reactions to the endoplasmic reticulum

Glucose-6-phosphate dehydrogenase is the rate-limiting enzyme of the oxidative pentose-phosphate pathway (OPPP). The OPPP mainly provides NADPH and sugar-phosphate building blocks for anabolic pathways and is present in all eukaryotes. In plant cells, the irreversible part of the OPPP is found in several compartments. Among the isoforms catalyzing the first OPPP step in Arabidopsis, G6PD1 to G6PD4 target plastids (with G6PD1 being also directed to peroxisomes), whereas G6PD5 and G6PD6 operate in the cytosol. We noticed that alternative splice forms G6PD5.4 and G6PD5.5 encode N-terminally extended proteoforms. Compared to G6PD5.1, RT-PCR signals differed and fluorescent reporter fusions expressed in Arabidopsis protoplasts accumulated in distinct intracellular sites. Co-expression with organelle-specific markers revealed that the G6PD5.4 and G6PD5.5 proteoforms label different subdomains of the endoplasmic reticulum (ER), and analysis of C-terminal roGFP fusions showed that their catalytic domains face the cytosol. In g6pd5-1 g6pd6-2 mutant protoplasts lacking cytosolic G6PDH activity, the ER-bound proteoforms were both active and thus able to form homomers. Among the Arabidopsis 6-phosphogluconolactonases (catalyzing the second OPPP step), we noticed that isoform PGL2 carries a C-terminal CaaX motif that may be prenylated for membrane attachment. Reporter-PGL2 fusions co-localized with G6PD5.4 in ER subdomains, which was abolished by Cys-to-Ser exchange in the ²⁵⁶CSIL motif. Among the Arabidopsis 6-phosphogluconate dehydrogenases (catalyzing the third OPPP step), S-acylated peptides were detected for all three isoforms in a recent palmitoylome, with dual cytosolic/peroxisomal PGD2 displaying three sites. Co-expression of GFP-PGD2 diminished crowding of OFP-G6PD5.4 at the ER, independent of PGL2's presence. Upon pull-down of GFP-G6PD5.4, not only unlabeled PGD2 and PGL2 were enriched, but also enzymes that depend on NADPH provision at the ER, indicative of physical interaction with the OPPP enzymes. When membrane-bound G6PD5.5 and 5.4 variants were co-expressed with KCR1 (ketoacyl-CoA reductase, involved in fatty acid elongation), ATR1 (NADPH:cytochrome-P450 oxidoreductase), or pulled C4H/CYP73A5 (cinnamate 4-hydroxylase) as indirectly (via ATR) NADPH-dependent cytochrome P450 enzyme, co-localization in ER subdomains was observed. Thus, alternative splicing of G6PD5 can direct the NADPH-producing OPPP reactions to the cytosolic face of the ER, where they may operate as membrane-bound metabolon to support several important biosynthetic pathways of plant cells.

Interactions of fungi with non-isothiocyanate products of the plant glucosinolate pathway: A review on product formation, antifungal activity, mode of action and biotransformation

The glucosinolate pathway, which is present in the order Brassicales, is one of the most researched defensive natural product biosynthesis pathways. Its core molecules, the glucosinolates are broken down upon pathogen challenge or tissue damage to yield an array of natural products that may help plants defend against the stressor. Though the most widely known glucosinolate decomposition products are the antimicrobial isothiocyanates, there is a wide range of other volatile and non-volatile natural products that arise from this biosynthetic pathway. This review summarizes our current knowledge on the interaction of these much less examined, non-isothiocyanate products with fungi. It deals with compounds including (1) glucosinolates and their biosynthesis precursors; (2) glucosinolate-derived nitriles (e.g. derivatives of 1H-indole-3-acetonitrile), thiocyanates, epithionitriles and oxazolidine-2-thiones; (3) putative isothiocyanate downstream products such as raphanusamic acid, 1H-indole-3-methanol (= indole-3-carbinol) and its oligomers, 1H-indol-3-ylmethanamine and ascorbigen; (4) 1H-indole-3-acetonitrile downstream products such as 1H-indole-3-carbaldehyde (indole-3-carboxaldehyde), 1H-indole-3-carboxylic acid and their derivatives; and (5) indole phytoalexins including brassinin, cyclobrassinin and brassilexin. Herein, a literature review on the following aspects is provided: their direct antifungal activity and the proposed mechanisms of antifungal action, increased biosynthesis after fungal challenge, as well as data on their biotransformation/detoxification by fungi, including but not limited to fungal myrosinase activity.

β-Cyanoalanine synthase protects mites against Arabidopsis defenses

Glucosinolates are antiherbivory chemical defense compounds in Arabidopsis (Arabidopsis thaliana). Specialist herbivores that feed on brassicaceous plants have evolved various mechanisms aimed at preventing the formation of toxic isothiocyanates. In contrast, generalist herbivores typically detoxify isothiocyanates through glutathione conjugation upon exposure. Here, we examined the response of an extreme generalist herbivore, the two-spotted spider mite Tetranychus urticae (Koch), to indole glucosinolates. Tetranychus urticae is a composite generalist whose individual populations have a restricted host range but have an ability to rapidly adapt to initially unfavorable plant hosts. Through comparative transcriptomic analysis of mite populations that have differential susceptibilities to Arabidopsis defenses, we identified β-cyanoalanine synthase of T. urticae (TuCAS), which encodes an enzyme with dual cysteine and β-cyanoalanine synthase activities. We combined Arabidopsis genetics, chemical complementation and mite reverse genetics to show that TuCAS is required for mite adaptation to Arabidopsis through its β-cyanoalanine synthase activity. Consistent with the β-cyanoalanine synthase role in detoxification of hydrogen cyanide (HCN), we discovered that upon mite herbivory, Arabidopsis plants release HCN. We further demonstrated that indole glucosinolates are sufficient for cyanide formation. Overall, our study uncovered Arabidopsis defenses that rely on indole glucosinolate-dependent cyanide for protection against mite herbivory. In response, Arabidopsis-adapted mites utilize the β-cyanoalanine synthase activity of TuCAS to counter cyanide toxicity, highlighting the mite's ability to activate resistant traits that enable this extreme polyphagous herbivore to exploit cyanogenic host plants.

Development of a quantification method for routine analysis of glucosinolates and camalexin in brassicaceous small-sized samples by simultaneous extraction prior to liquid chromatography determination

Glucosinolates and camalexin are secondary metabolites that, as phytoanticipins and phytoalexins, play a crucial role in plant defence. The present work proposes an improved analytical method for routine analysis and quantification of glucosinolates and camalexin in brassicaceous small-sized samples by using the very specific desulfation process of glucosinolates analysis and the specificity of fluorescence detection for camalexin analysis. The approach is based on a simultaneous ultrasound-assisted extraction followed by a purification on an anion-exchange column. Final analyses are conducted by HPLC-UV-MS for desulfo-glucosinolates and HPLC coupled to a fluorescence detector (HPLC-FLD) for camalexin. The method is linear for glucosinolates (50-3500 µM) and camalexin (0.025-5 µg.mL^-1) with an LOD/LOQ of 3.8/12.6 µM and 0.014/0.046 µg.mL^-1 respectively. The method demonstrated adequate precision, accuracy and trueness on certified reference rapeseed. A practical application of our approach was conducted on different Brassicaceae genera (Barbarea vulgaris, Brassica nigra, Capsella bursa-pastoris, Cardamine hirsuta, Coincya monensis, Sinapis arvensis, and Sisymbrium officinale) and Arabidopsis thaliana genotypes (Columbia and Wassilewskija). Futhermore, different plant organs (seeds and leaves) were analysed, previously inoculated or not with the pathogenic fungus Alternaria brassicicola.

Molecular mechanisms associated with microbial biostimulant-mediated growth enhancement, priming and drought stress tolerance in maize plants

Microbial-based biostimulants are emerging as effective strategies to improve agricultural productivity; however, the modes of action of such formulations are still largely unknown. Thus, herein we report elucidated metabolic reconfigurations in maize (Zea mays) leaves associated with growth promotion and drought stress tolerance induced by a microbial-based biostimulant, a Bacillus consortium. Morphophysiological measurements revealed that the biostimulant induced a significant increase in biomass and enzymatic regulators of oxidative stress. Furthermore, the targeted metabolomics approach revealed differential quantitative profiles in amino acid-, phytohormone-, flavonoid- and phenolic acid levels in plants treated with the biostimulant under well-watered, mild, and severe drought stress conditions. These metabolic alterations were complemented with gene expression and global DNA methylation profiles. Thus, the postulated framework, describing biostimulant-induced metabolic events in maize plants, provides actionable knowledge necessary for industries and farmers to confidently and innovatively explore, design and fully implement microbial-based formulations and strategies into agronomic practices for sustainable agriculture and food production.

Camalexin accumulation as a component of plant immunity during interactions with pathogens and beneficial microbes

This review provides an overview on the role of camalexin in plant immunity taking into account various plant-pathogen and beneficial microbe interactions, regulation mechanisms and the contribution in basal and induced plant resistance. In a hostile environment, plants evolve complex and sophisticated defense mechanisms to counteract invading pathogens and herbivores. Several lines of evidence support the assumption that secondary metabolites like phytoalexins which are synthesized de novo, play an important role in plant defenses and contribute to pathogens' resistance in a wide variety of plant species. Phytoalexins are synthesized and accumulated in plants upon pathogen challenge, root colonization by beneficial microbes, following treatment with chemical elicitors or in response to abiotic stresses. Their protective properties against pathogens have been reported in various plant species as well as their contribution to human health. Phytoalexins are synthesized through activation of particular sets of genes encoding specific pathways. Camalexin (3'-thiazol-2'-yl-indole) is the primary phytoalexin produced by Arabidopsis thaliana after microbial infection or abiotic elicitation and an iconic representative of the indole phytoalexin family. The synthesis of camalexin is an integral part of cruciferous plant defense mechanisms. Although the pathway leading to camalexin has been largely elucidated, the regulatory networks that control the induction of its biosynthetic steps by pathogens with different lifestyles or by beneficial microbes remain mostly unknown. This review thus presents current knowledge regarding camalexin biosynthesis induction during plant-pathogen and beneficial microbe interactions as well as in response to microbial compounds and provides an overview on its regulation and interplay with signaling pathways. The contribution of camalexin to basal and induced plant resistance and its detoxification by some pathogens to overcome host resistance are also discussed.

Streptozotocin-Induced Hyperglycemia Is Associated with Unique Microbiome Metabolomic Signatures in Response to Ciprofloxacin Treatment

It is well recognized that the microbiome plays key roles in human health, and that damage to this system by, for example, antibiotic administration has detrimental effects. With this, there is collective recognition that off-target antibiotic susceptibility within the microbiome is a particularly troublesome side effect that has serious impacts on host well-being. Thus, a pressing area of research is the characterization of antibiotic susceptibility determinants within the microbiome, as understanding these mechanisms may inform the development of microbiome-protective therapeutic strategies. In particular, metabolic environment is known to play a key role in the different responses of this microbial community to antibiotics. Here, we explore the role of host dysglycemia on ciprofloxacin susceptibility in the murine cecum. We used a combination of 16S rRNA sequencing and untargeted metabolomics to characterize changes in both microbiome taxonomy and environment. We found that dysglycemia minimally impacted ciprofloxacin-associated changes in microbiome structure. However, from a metabolic perspective, host hyperglycemia was associated with significant changes in respiration, central carbon metabolism, and nucleotide synthesis-related metabolites. Together, these data suggest that host glycemia may influence microbiome function during antibiotic challenge.

Research progress of aldehyde oxidases in plants

Plant aldehyde oxidases (AOs) are multi-functional enzymes, and they could oxidize abscisic aldehyde into ABA (abscisic acid) or indole acetaldehyde into IAA (indoleacetic acid) as the last step, respectively. AOs can be divided into four groups based on their biochemical and physiological functions. In this review, we summarized the recent studies about AOs in plants including the motif information, biochemical, and physiological functions. Besides their role in phytohormones biosynthesis and stress response, AOs could also involve in reactive oxygen species homeostasis, aldehyde detoxification and stress tolerance.

EDB Gene Cluster-Dependent Indole Production Is Responsible for the Ability of Pseudomonas fluorescens NZI7 to Repel Grazing by Caenorhabditis elegans

The "EDB" (from "edible") gene cluster, a variant of the ebo cluster of genes found in many bacteria and algae, allows Pseudomonas fluorescens NZI7 (referred to here as "NZI7") to repel grazing by the nematode Caenorhabditis elegans. The mechanism underlying this phenotype is unknown. Here we report that the EDB cluster is involved in the conversion of tryptophan to (1H-indol-3-yl)-oxoacetamide, indole 3-aldehyde, and other indole-derived compounds. Inactivation of the EDB genes in NZI7 resulted in mutants that lack the ability to excrete indole-derived compounds as well as the ability to repel C. elegans. Heterologous expression of the NZI7 EDB cluster in E. coli cultivated in minimal M9 medium containing 2 mM l-tryptophan also released indole derivatives including tryptophol, 3-(hydroxyacetyl)indole, colletotryptin E, and two new dimeric indoles. Expression of the NZI7 EDB cluster in E. coli, cultured in minimal M9 medium and lacking tryptophan, did not produce detectable levels of indole derivatives. Both (1H-indol-3-yl)-oxoacetamide and indole 3-aldehyde showed repellent activity against C. elegans, revealing the mechanism underlying the ability of P. fluorescens NZI7 to repel grazing by C. elegans.

MAG2 and MAL Regulate Vesicle Trafficking and Auxin Homeostasis With Functional Redundancy

Auxin is a central phytohormone and controls almost all aspects of plant development and stress response. Auxin homeostasis is coordinately regulated by biosynthesis, catabolism, transport, conjugation, and deposition. Endoplasmic reticulum (ER)-localized MAIGO2 (MAG2) complex mediates tethering of arriving vesicles to the ER membrane, and it is crucial for ER export trafficking. Despite important regulatory roles of MAG2 in vesicle trafficking, the mag2 mutant had mild developmental abnormalities. MAG2 has one homolog protein, MAG2-Like (MAL), and the mal-1 mutant also had slight developmental phenotypes. In order to investigate MAG2 and MAL regulatory function in plant development, we generated the mag2-1 mal-1 double mutant. As expected, the double mutant exhibited serious developmental defects and more alteration in stress response compared with single mutants and wild type. Proteomic analysis revealed that signaling, metabolism, and stress response in mag2-1 mal-1 were affected, especially membrane trafficking and auxin biosynthesis, signaling, and transport. Biochemical and cell biological analysis indicated that the mag2-1 mal-1 double mutant had more serious defects in vesicle transport than the mag2-1 and mal-1 single mutants. The auxin distribution and abundance of auxin transporters were altered significantly in the mag2-1 and mal-1 single mutants and mag2-1 mal-1 double mutant. Our findings suggest that MAG2 and MAL regulate plant development and auxin homeostasis by controlling membrane trafficking, with functional redundancy.

Metabolic Circuits in Sap Extracts Reflect the Effects of a Microbial Biostimulant on Maize Metabolism under Drought Conditions

The use of microbial biostimulants in the agricultural sector is increasingly gaining momentum and drawing scientific attention to decode the molecular interactions between the biostimulants and plants. Although these biostimulants have been shown to improve plant health and development, the underlying molecular phenomenology remains enigmatic. Thus, this study is a metabolomics work to unravel metabolic circuits in sap extracts from maize plants treated with a microbial biostimulant, under normal and drought conditions. The biostimulant, which was a consortium of different Bacilli strains, was applied at the planting stage, followed by drought stress application. The maize sap extracts were collected at 5 weeks after emergence, and the extracted metabolites were analyzed on liquid chromatography-mass spectrometry platforms. The acquired data were mined using chemometrics and bioinformatics tools. The results showed that under both well-watered and drought stress conditions, the application of the biostimulant led to differential changes in the profiles of amino acids, hormones, TCA intermediates, phenolics, steviol glycosides and oxylipins. These metabolic changes spanned several biological pathways and involved a high correlation of the biochemical as well as structural metabolic relationships that coordinate the maize metabolism. The hypothetical model, postulated from this study, describes metabolic events induced by the microbial biostimulant for growth promotion and enhanced defences. Such understanding of biostimulant-induced changes in maize sap pinpoints to the biochemistry and molecular mechanisms that govern the biostimulant-plant interactions, which contribute to ongoing efforts to generate actionable knowledge of the molecular and physiological mechanisms that define modes of action of biostimulants.

A Possible Mode of Action of Methyl Jasmonate to Induce the Secondary Abscission Zone in Stems of Bryophyllum calycinum: Relevance to Plant Hormone Dynamics

Plants can react to environmental stresses through the abscission of infected, damaged, or senescent organs. A possible mode of action of methyl jasmonate (JA-Me) to induce the formation of the secondary abscission zone (SAZ) in the stems of Bryophyllum calycinum was investigated concerning plant hormone dynamics. Internode segments were prepared mainly from the second or third internode from the top of plants with active elongation. JA-Me applied to the middle of internode segments induced the SAZ formation above and below the treatment after 5-7 days. At 6 to 7 days after JA-Me treatment, the above and below internode pieces adjacent to the SAZ were excised and subjected to comprehensive analyses of plant hormones. The endogenous levels of auxin-related compounds between both sides adjacent to the SAZ were quite different. No differences were observed in the level of jasmonic acid (JA), but the contents of 12-oxo-phytodienoic acid (OPDA), a precursor of JA, and N-jasmonyl-leucine (JA-Leu) substantially decreased on the JA-Me side. Almost no effects of JA-Me on the dynamics of other plant hormones (cytokinins, abscisic acid, and gibberellins) were observed. Similar JA-Me effects on plant hormones and morphology were observed in the last internode of the decapitated growing plants. These suggest that the application of JA-Me induces the SAZ in the internode of B. calycinum by affecting endogenous levels of auxin- and jasmonate-related compounds.

Streptozotocin-induced hyperglycemia alters the cecal metabolome and exacerbates antibiotic-induced dysbiosis

It is well established in the microbiome field that antibiotic (ATB) use and metabolic disease both impact the structure and function of the gut microbiome. But how host and microbial metabolism interacts with ATB susceptibility to affect the resulting dysbiosis remains poorly understood. In a streptozotocin-induced model of hyperglycemia (HG), we use a combined metagenomic, metatranscriptomic, and metabolomic approach to profile changes in microbiome taxonomic composition, transcriptional activity, and metabolite abundance both pre- and post-ATB challenge. We find that HG impacts both microbiome structure and metabolism, ultimately increasing susceptibility to amoxicillin. HG exacerbates drug-induced dysbiosis and increases both phosphotransferase system activity and energy catabolism compared to controls. Finally, HG and ATB co-treatment increases pathogen susceptibility and reduces survival in a Salmonella enterica infection model. Our data demonstrate that induced HG is sufficient to modify the cecal metabolite pool, worsen the severity of ATB dysbiosis, and decrease colonization resistance.

Arabidopsis aldehyde oxidase 3, known to oxidize abscisic aldehyde to abscisic acid, protects leaves from aldehyde toxicity

The Arabidopsis thaliana aldehyde oxidase 3 (AAO3) catalyzes the oxidation of abscisic aldehyde (ABal) to abscisic acid (ABA). Besides ABal, plants generate other aldehydes that can be toxic above a certain threshold. AAO3 knockout mutants (aao3) exhibited earlier senescence but equivalent relative water content compared with wild-type (WT) during normal growth or upon application of UV-C irradiation. Aldehyde profiling in leaves of 24-day-old plants revealed higher accumulation of acrolein, crotonaldehyde, 3Z-hexenal, hexanal and acetaldehyde in aao3 mutants compared with WT leaves. Similarly, higher levels of acrolein, benzaldehyde, crotonaldehyde, propionaldehyde, trans-2-hexenal and acetaldehyde were accumulated in aao3 mutants upon UV-C irradiation. Aldehydes application to plants hastened profuse senescence symptoms and higher accumulation of aldehydes, such as acrolein, benzaldehyde and 4-hydroxy-2-nonenal, in aao3 mutant leaves as compared with WT. The senescence symptoms included greater decrease in chlorophyll content and increase in transcript expression of the early senescence marker genes, Senescence-Related-Gene1, Stay-Green-Protein2 as well as NAC-LIKE, ACTIVATED-BY AP3/P1. Notably, although aao3 had lower ABA content than WT, members of the ABA-responding genes SnRKs were expressed at similar levels in aao3 and WT. Moreover, the other ABA-deficient mutants [aba2 and 9-cis-poxycarotenoid dioxygenase3-2 (nced3-2), that has functional AAO3] exhibited similar aldehydes accumulation and chlorophyll content like WT under normal growth conditions or UV-C irradiation. These results indicate that the absence of AAO3 oxidation activity and not the lower ABA and its associated function is responsible for the earlier senescence symptoms in aao3 mutant.

Insect eggs trigger systemic acquired resistance against a fungal and an oomycete pathogen

Plants are able to detect insect eggs deposited on leaves. In Arabidopsis, eggs of the butterfly species Pieris brassicae (common name large white) induce plant defenses and activate the salicylic acid (SA) pathway. We previously discovered that oviposition triggers a systemic acquired resistance (SAR) against the bacterial hemibiotroph pathogen Pseudomonas syringae. Here, we show that insect eggs or treatment with egg extract (EE) induce SAR against the fungal necrotroph Botrytis cinerea BMM and the oomycete pathogen Hyaloperonospora arabidopsidis Noco2. This response is abolished in ics1, ald1 and fmo1, indicating that the SA pathway and the N-hydroxypipecolic acid (NHP) pathway are involved. Establishment of EE-induced SAR in distal leaves potentially involves tryptophan-derived metabolites, including camalexin. Indeed, SAR is abolished in the biosynthesis mutants cyp79B2 cyp79B3, cyp71a12 cyp71a13 and pad3-1, and camalexin is toxic to B. cinerea in vitro. This study reveals an interesting mechanism by which lepidopteran eggs interfere with plant-pathogen interactions.

High-resolution imaging as a tool for identifying quantitative trait loci that regulate photomorphogenesis in Arabidopsis thaliana

A primary component of seedling establishment is the photomorphogenic response as seedlings emerge from the soil. This process is characterized by a reduced growth rate in the hypocotyl, increased root growth, opening of the apical hook and expansion of the cotyledons as photosynthetic organs. While fundamental to plant success, the photomorphogenic response can be highly variable. Additionally, studies of Arabidopsis thaliana are made difficult by subtle differences in growth rate between individuals. High-resolution imaging and computational processing have emerged as useful tools for quantification of such phenotypes. This study sought to: (i) develop an imaging methodology which could capture changes in growth rate as seedlings transition from darkness to blue light in real time, and (ii) apply this methodology to single-quantitative trait locus (QTL) analysis using the Cvi × Ler recombinant inbred line (RIL) mapping population. Significant differences in the photomorphogenic response were observed between the parent lines and analysis of 158 RILs revealed a wide range of growth rate phenotypes. Quantitative trait locus analysis detected significant loci associated with dark growth rate on chromosome 5 and significant loci associated with light growth rate on chromosome 2. Candidate genes associated with these loci, such as the previously characterized ER locus, highlight the application of this approach for QTL analysis. Genetic analysis of Landsberg lines without the erecta mutation also supports a role for ER in modulating the photomorphogenic response, consistent with previous QTL analyses of this population. Strengths and limitations of this methodology are presented, as well as means of improvement.

Multiple indole glucosinolates and myrosinases defend Arabidopsis against Tetranychus urticae herbivory

Arabidopsis (Arabidopsis thaliana) defenses against herbivores are regulated by the jasmonate (JA) hormonal signaling pathway, which leads to the production of a plethora of defense compounds. Arabidopsis defense compounds include tryptophan-derived metabolites, which limit Arabidopsis infestation by the generalist herbivore two-spotted spider mite, Tetranychus urticae. However, the phytochemicals responsible for Arabidopsis protection against T. urticae are unknown. Here, we used Arabidopsis mutants disrupted in the synthesis of tryptophan-derived secondary metabolites to identify phytochemicals involved in the defense against T. urticae. We show that of the three tryptophan-dependent pathways found in Arabidopsis, the indole glucosinolate (IG) pathway is necessary and sufficient to assure tryptophan-mediated defense against T. urticae. We demonstrate that all three IGs can limit T. urticae herbivory, but that they must be processed by myrosinases to hinder T. urticae oviposition. Putative IG breakdown products were detected in mite-infested leaves, suggesting in planta processing by myrosinases. Finally, we demonstrate that besides IGs, there are additional JA-regulated defenses that control T. urticae herbivory. Together, our results reveal the complexity of Arabidopsis defenses against T. urticae that rely on multiple IGs, specific myrosinases, and additional JA-dependent defenses.

3-Indoleacetonitrile Is Highly Effective in Treating Influenza A Virus Infection In Vitro and In Vivo

Influenza A viruses are serious zoonotic pathogens that continuously cause pandemics in several animal hosts, including birds, pigs, and humans. Indole derivatives containing an indole core framework have been extensively studied and developed to prevent and/or treat viral infection. This study evaluated the anti-influenza activity of several indole derivatives, including 3-indoleacetonitrile, indole-3-carboxaldehyde, 3-carboxyindole, and gramine, in A549 and MDCK cells. Among these compounds, 3-indoleacetonitrile exerts profound antiviral activity against a broad spectrum of influenza A viruses, as tested in A549 cells. Importantly, in a mouse model, 3-indoleacetonitrile with a non-toxic concentration of 20 mg/kg effectively reduced the mortality and weight loss, diminished lung virus titers, and alleviated lung lesions of mice lethally challenged with A/duck/Hubei/WH18/2015 H5N6 and A/Puerto Rico/8/1934 H1N1 influenza A viruses. The antiviral properties enable the potential use of 3-indoleacetonitrile for the treatment of IAV infection.

Ganoderma lucidum promotes sleep through a gut microbiota-dependent and serotonin-involved pathway in mice

Ganoderma lucidum is a medicinal mushroom used in traditional Chinese medicine with putative tranquilizing effects. However, the component of G. lucidum that promotes sleep has not been clearly identified. Here, the effect and mechanism of the acidic part of the alcohol extract of G. lucidum mycelia (GLAA) on sleep were studied in mice. Administration of 25, 50 and 100 mg/kg GLAA for 28 days promoted sleep in pentobarbital-treated mice by shortening sleep latency and prolonging sleeping time. GLAA administration increased the levels of the sleep-promoting neurotransmitter 5-hydroxytryptamine and the Tph2, Iptr3 and Gng13 transcripts in the sleep-regulating serotonergic synapse pathway in the hypothalamus during this process. Moreover, GLAA administration reduced lipopolysaccharide and raised peptidoglycan levels in serum. GLAA-enriched gut bacteria and metabolites, including Bifidobacterium, Bifidobacterium animalis, indole-3-carboxylic acid and acetylphosphate were negatively correlated with sleep latency and positively correlated with sleeping time and the hypothalamus 5-hydroxytryptamine concentration. Both the GLAA sleep promotion effect and the altered faecal metabolites correlated with sleep behaviours disappeared after gut microbiota depletion with antibiotics. Our results showed that GLAA promotes sleep through a gut microbiota-dependent and serotonin-associated pathway in mice.

Metabolite profiling reveals a role for intercellular dihydrocamalexic acid in the response of mature Arabidopsis thaliana to Pseudomonas syringae

The leaf intercellular space is a site of plant-microbe interactions where pathogenic bacteria such as Pseudomonas syringae grow. In Arabidopsis thaliana, the biosynthesis of tryptophan-derived indolic metabolites is induced by P. syringae infection. Using high-resolution mass spectrometry-based profiling and biosynthetic mutants, we investigated the role of indolic compounds and other small molecules in the response of mature Arabidopsis to P. syringae. We observed dihydrocamalexic acid (DHCA), the precursor to the defense-related compound camalexin, accumulating in intercellular washing fluids (IWFs) without further conversion to camalexin. The indolic biosynthesis mutant cyp71a12/cyp71a13 was more susceptible to P. syringae compared to mature wild-type plants displaying age-related resistance (ARR). DHCA and structural analogs inhibit P. syringae growth (MIC ~ 500 μg/mL), but not at concentrations found in IWFs, and DHCA did not inhibit biofilm formation in vitro. However, infiltration of exogenous DHCA enhanced resistance in mature cyp71a12/cyp71a13. These results provide evidence that DHCA derived from CYP71A12 and CYP71A13 activity accumulates in the intercellular space and contributes to the resistance of mature Arabidopsis to P. syringae without directly inhibiting bacterial growth.

The chemical compound 'Heatin' stimulates hypocotyl elongation and interferes with the Arabidopsis NIT1-subfamily of nitrilases

Temperature passively affects biological processes involved in plant growth. Therefore, it is challenging to study the dedicated temperature signalling pathways that orchestrate thermomorphogenesis, a suite of elongation growth-based adaptations that enhance leaf-cooling capacity. We screened a chemical library for compounds that restored hypocotyl elongation in the pif4-2-deficient mutant background at warm temperature conditions in Arabidopsis thaliana to identify modulators of thermomorphogenesis. The small aromatic compound 'Heatin', containing 1-iminomethyl-2-naphthol as a pharmacophore, was selected as an enhancer of elongation growth. We show that ARABIDOPSIS ALDEHYDE OXIDASES redundantly contribute to Heatin-mediated hypocotyl elongation. Following a chemical proteomics approach, the members of the NITRILASE1-subfamily of auxin biosynthesis enzymes were identified among the molecular targets of Heatin. Our data reveal that nitrilases are involved in promotion of hypocotyl elongation in response to high temperature and Heatin-mediated hypocotyl elongation requires the NITRILASE1-subfamily members, NIT1 and NIT2. Heatin inhibits NIT1-subfamily enzymatic activity in vitro and the application of Heatin accordingly results in the accumulation of NIT1-subfamily substrate indole-3-acetonitrile in vivo. However, levels of the NIT1-subfamily product, bioactive auxin (indole-3-acetic acid), were also significantly increased. It is likely that the stimulation of hypocotyl elongation by Heatin might be independent of its observed interaction with NITRILASE1-subfamily members. However, nitrilases may contribute to the Heatin response by stimulating indole-3-acetic acid biosynthesis in an indirect way. Heatin and its functional analogues present novel chemical entities for studying auxin biology.

A Network of Phosphate Starvation and Immune-Related Signaling and Metabolic Pathways Controls the Interaction between Arabidopsis thaliana and the Beneficial Fungus Colletotrichum tofieldiae

The beneficial root-colonizing fungus Colletotrichum tofieldiae mediates plant growth promotion (PGP) upon phosphate (Pi) starvation in Arabidopsis thaliana. This activity is dependent on the Trp metabolism of the host, including indole glucosinolate (IG) hydrolysis. Here, we show that C. tofieldiae resolves several Pi starvation-induced molecular processes in the host, one of which is the downregulation of auxin signaling in germ-free plants, which is restored in the presence of the fungus. Using CRISPR/Cas9 genome editing, we generated an Arabidopsis triple mutant lacking three homologous nitrilases (NIT1 to NIT3) that are thought to link IG-hydrolysis products with auxin biosynthesis. Retained C. tofieldiae-induced PGP in nit1/2/3 mutant plants demonstrated that this metabolic connection is dispensable for the beneficial activity of the fungus. This suggests that either there is an alternative metabolic link between IG-hydrolysis products and auxin biosynthesis, or C. tofieldiae restores auxin signaling independently of IG metabolism. We show that C. tofieldiae, similar to pathogenic microorganisms, triggers Arabidopsis immune pathways that rely on IG metabolism as well as salicylic acid and ethylene signaling. Analysis of IG-deficient myb mutants revealed that these metabolites are, indeed, important for control of in planta C. tofieldiae growth: however, enhanced C. tofieldiae biomass does not necessarily negatively correlate with PGP. We show that Pi deficiency enables more efficient colonization of Arabidopsis by C. tofieldiae, possibly due to the MYC2-mediated repression of ethylene signaling and changes in the constitutive IG composition in roots.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

A biosensor for the direct visualization of auxin

One of the most important regulatory small molecules in plants is indole-3-acetic acid, also known as auxin. Its dynamic redistribution has an essential role in almost every aspect of plant life, ranging from cell shape and division to organogenesis and responses to light and gravity1,2. So far, it has not been possible to directly determine the spatial and temporal distribution of auxin at a cellular resolution. Instead it is inferred from the visualization of irreversible processes that involve the endogenous auxin-response machinery3-7; however, such a system cannot detect transient changes. Here we report a genetically encoded biosensor for the quantitative in vivo visualization of auxin distribution. The sensor is based on the Escherichia coli tryptophan repressor8, the binding pocket of which is engineered to be specific to auxin. Coupling of the auxin-binding moiety with selected fluorescent proteins enables the use of a fluorescence resonance energy transfer signal as a readout. Unlike previous systems, this sensor enables direct monitoring of the rapid uptake and clearance of auxin by individual cells and within cell compartments in planta. By responding to the graded spatial distribution along the root axis and its perturbation by transport inhibitors-as well as the rapid and reversible redistribution of endogenous auxin in response to changes in gravity vectors-our sensor enables real-time monitoring of auxin concentrations at a (sub)cellular resolution and their spatial and temporal changes during the lifespan of a plant.

Enantioselective effects of imazethapyr on the secondary metabolites and nutritional value of wheat seedlings

The secondary metabolism of plants is key for mediating responses to environmental stress, but few studies have examined how the relationship between secondary metabolism and the stress response of plants is affected by exposure to chiral herbicides. Here, we studied the enantioselective disturbance of the chiral herbicide imazethapyr (IM) on the secondary metabolism and nutrient levels of wheat seedlings. The bioactive enantiomer R-IM significantly increased the contents of major secondary metabolites, including phenolic acids, flavonoids, and carotenoids but greatly inhibited the production of benzoxazine. The antioxidant system also responded strongly to R-IM; specifically, the activities of SOD, CAT, and GPX enzymes were all significantly induced, and the GSH content initially increased but then decreased. Furthermore, the nutrient levels of wheat seedlings were also affected; dietary fiber content decreased, while the contents of the microelements Fe, Mn, and Zn increased. In sum, this study provides new insight into the phytotoxic effects of IM and raises new questions on the role of secondary metabolites and nutrients in mediating enantioselective effects.

Regulation of glucosinolate biosynthesis

Glucosinolates are secondary defense metabolites produced by plants of the order Brassicales, which includes the model species Arabidopsis and many crop species. In the past 13 years, the regulation of glucosinolate synthesis in plants has been intensively studied, with recent research revealing complex molecular mechanisms that connect glucosinolate production with responses to other central pathways. In this review, we discuss how the regulation of glucosinolate biosynthesis is ecologically relevant for plants, how it is controlled by transcription factors, and how this transcriptional machinery interacts with hormonal, environmental, and epigenetic mechanisms. We present the central players in glucosinolate regulation, MYB and basic helix-loop-helix transcription factors, as well as the plant hormone jasmonate, which together with other hormones and environmental signals allow the coordinated and rapid regulation of glucosinolate genes. Furthermore, we highlight the regulatory connections between glucosinolates, auxin, and sulfur metabolism and discuss emerging insights and open questions on the regulation of glucosinolate biosynthesis.

Tryptophan-derived metabolites and BAK1 separately contribute to Arabidopsis postinvasive immunity against Alternaria brassicicola

Nonhost resistance of Arabidopsis thaliana against the hemibiotrophic fungus Colletotrichum tropicale requires PEN2-dependent preinvasive resistance and CYP71A12 and CYP71A13-dependent postinvasive resistance, which both rely on tryptophan (Trp) metabolism. We here revealed that CYP71A12, CYP71A13 and PAD3 are critical for Arabidopsis' postinvasive basal resistance toward the necrotrophic Alternaria brassicicola. Consistent with this, gene expression and metabolite analyses suggested that the invasion by A. brassicicola triggered the CYP71A12-dependent production of indole-3-carboxylic acid derivatives and the PAD3 and CYP71A13-dependent production of camalexin. We next addressed the activation of the CYP71A12 and PAD3-dependent postinvasive resistance. We found that bak1-5 mutation significantly reduced postinvasive resistance against A. brassicicola, indicating that pattern recognition contributes to activation of this second defense-layer. However, the bak1-5 mutation had no detectable effects on the Trp-metabolism triggered by the fungal penetration. Together with this, further comparative gene expression analyses suggested that pathogen invasion in Arabidopsis activates (1) CYP71A12 and PAD3-related antifungal metabolism that is not hampered by bak1-5, and (2) a bak1-5 sensitive immune pathway that activates the expression of antimicrobial proteins.

Silver nanoparticles affect phenolic and phytoalexin composition of Arabidopsis thaliana

Silver nanoparticles are widely used in industry, medicine, biotechnology and agriculture. As a consequence, these nanoparticles are reaching the environment as waste products, which might have a negative impact on the environment, especially on plants. This includes the elicitation of various biochemical processes in plants. In this article, we report on the changes in secondary metabolic profile of Arabidopsis thaliana seedlings subjected to silver nanoparticle treatment in vitro. Briefly, various sizes (10 nm, 40 nm and 100 nm in diameter) and concentrations (0.5-5.0 ppm) of silver nanoparticles were tested. Ultraperformance liquid chromatography coupled with ultraviolet and fluorescence detectors as well as hyphenated to a high-resolution mass spectrometer (UPLC-PDA-FLR, UPLC-HESI-HRMS) and HPLC - ion trap mass spectrometer (HPLC-ESI-MS/MS), were applied to identify and quantify secondary metabolites. To understand whether silver ions could induce changes in the secondary metabolite profile, seedlings treated with silver nitrate in concentrations equivalent to these of nanoparticles were also analysed. The results showed significant differences in the accumulation of phenolic and indole compounds between treatments. Silver nanoparticles and silver ions induced the biosynthesis of camalexin, hydroxycamalexin O-hexoside and hydroxycamalexin malonyl-hexoside. These compounds are important phytoalexins for Brassicaceae family (especially for Camelinae clad) and are also synthetized in response to biotic and abiotic stresses. Statistically significant changes have been also observed for five phenolic compounds and 5'Glucosyl-dihydroneoascorbigen in different treatment conditions.

Reactive oxygen species dosage in Arabidopsis chloroplasts can improve resistance towards Colletotrichum higginsianum by the induction of WRKY33

Arabidopsis plants overexpressing glycolate oxidase in chloroplasts (GO5) and loss-of-function mutants of the major peroxisomal catalase isoform, cat2-2, produce increased hydrogen peroxide (H₂ O₂ ) amounts from the respective organelles when subjected to photorespiratory conditions like increased light intensity. Here, we have investigated if and how the signaling processes triggered by H₂ O₂ production in response to shifts in environmental conditions and the concomitant induction of indole phytoalexin biosynthesis in GO5 affect susceptibility towards the hemibiotrophic fungus Colletotrichum higginsianum. Combining histological, biochemical, and molecular assays, we found that the accumulation of the phytoalexin camalexin was comparable between GO genotypes and cat2-2 in the absence of pathogen. Compared with wild-type, GO5 showed improved resistance after light-shift-mediated production of H₂ O₂ , whereas cat2-2 became more susceptible and allowed significantly more pathogen entry. Unlike GO5, cat2-2 suffered from severe oxidative stress after light shifts, as indicated by glutathione pool size and oxidation state. We discuss a connection between elevated oxidative stress and dampened induction of salicylic acid mediated defense in cat2-2. Genetic analyses demonstrated that induced resistance of GO5 is dependent on WRKY33, but not on camalexin production. We propose that indole carbonyl nitriles might play a role in defense against C. higginsianum.

High-throughput non-targeted metabolomics study of the effects of perfluorooctane sulfonate (PFOS) on the metabolic characteristics of A. thaliana leaves

The ecotoxicity of perfluorooctane sulfonate (PFOS) is complex and has been reported in animals (including fish and mice), but the effects of PFOS in plants, especially the toxic mechanisms, have rarely been studied. High-throughput nontargeted metabolomics methods for comprehensive assessment were selected to study changes in metabolic characteristics in Arabidopsis thaliana leaves by exposure to different concentrations of PFOS throughout the growth period (30 days). All the metabolites were analyzed by PCA and OPLS-DA methods, by the cutoff of VIP and p-value, 53 biomarkers were found and significantly regulated, all amino acids except glutamate were inhibited and probably associated with binding to protein, auxin and cytokinin of phytohormones were significantly down-regulated. In response mechanism to oxidative stress from PFOS, the phenylpropanoid pathway were fully activated to form several polyphenols and further enhanced into several flavonoids against the reactive oxygen species (ROS) as the primary defend pathway, in addition, ascorbate, trehalose and nicotinamide also were activated and help decrease the damage from oxidative stress. These results provide insights into the mechanism underlying the phytotoxicity of PFOS.

Targeted Isolation of Indole Alkaloids from Streptomyces sp. CT37

Four compounds (1-4) were isolated from the extracts of Streptomyces sp. CT37 using bioassay in conjunction with mass spectrometric molecular networking (MN) driven isolation. Their complete structures were established by high-resolution electrospray ionization mass spectrometry (HR-ESIMS), and 1D and 2D nuclear magnetic resonance (NMR) data. Legonimide 1 was identified as a new alkaloid containing a rare linear imide motif in its structure, while compounds 2-4 were already known and their structures were elucidated as 1H-indole-3-carbaldehyde, actinopolymorphol B, (2R,3R)-1-phenylbutane-2,3-diol, respectively. The biosynthetic pathways of 1-4 were proposed based on the reported biogenesis of indole alkaloids in literature. Bioactivity tests for 1 and 2 revealed moderate growth inhibition activity against Candida albicans ATCC 10231 with MIC95 values of 21.54 µg/mL and 11.47 µg/mL, respectively.

The dynamic response of the Arabidopsis root metabolome to auxin and ethylene is not predicted by changes in the transcriptome

While the effects of phytohormones on plant gene expression have been well characterized, comparatively little is known about how hormones influence metabolite profiles. This study examined the effects of elevated auxin and ethylene on the metabolome of Arabidopsis roots using a high-resolution 24 h time course, conducted in parallel to time-matched transcriptomic analyses. Mass spectrometry using orthogonal UPLC separation strategies (reversed phase and HILIC) in both positive and negative ionization modes was used to maximize identification of metabolites with altered levels. The findings show that the root metabolome responds rapidly to hormone stimulus and that compounds belonging to the same class of metabolites exhibit similar changes. The responses were dominated by changes in phenylpropanoid, glucosinolate, and fatty acid metabolism, although the nature and timing of the response was unique for each hormone. These alterations in the metabolome were not directly predicted by the corresponding transcriptome data, suggesting that post-transcriptional events such as changes in enzyme activity and/or transport processes drove the observed changes in the metabolome. These findings underscore the need to better understand the biochemical mechanisms underlying the temporal reconfiguration of plant metabolism, especially in relation to the hormone-metabolome interface and its subsequent physiological and morphological effects.

Trichoderma parareesei Favors the Tolerance of Rapeseed (Brassica napus L.) to Salinity and Drought Due to a Chorismate Mutase

Both drought and salinity represent the greatest plant abiotic stresses in crops. Increasing plant tolerance against these environmental conditions must be a key strategy in the development of future agriculture. The genus of Trichoderma filament fungi includes several species widely used as biocontrol agents for plant diseases but also some with the ability to increase plant tolerance against abiotic stresses. In this sense, using the species T. parareesei and T. harzianum, we have verified the differences between the two after their application in rapeseed (Brassica napus) root inoculation, with T. parareesei being a more efficient alternative to increase rapeseed productivity under drought or salinity conditions. In addition, we have determined the role that T. parareesei chorismate mutase plays in its ability to promote tolerance to salinity and drought in plants by increasing the expression of genes related to the hormonal pathways of abscisic acid (ABA) under drought stress, and ethylene (ET) under salt stress.

The role of CYP71A12 monooxygenase in pathogen-triggered tryptophan metabolism and Arabidopsis immunity

Effective defense of Arabidopsis against filamentous pathogens requires two mechanisms, both of which involve biosynthesis of tryptophan (Trp)-derived metabolites. Extracellular resistance involves products of PEN2-dependent metabolism of indole glucosinolates (IGs). Restriction of further fungal growth requires PAD3-dependent camalexin and other, as yet uncharacterized, indolics. This study focuses on the function of CYP71A12 monooxygenase in pathogen-triggered Trp metabolism, including the biosynthesis of indole-3-carboxylic acid (ICA). Moreover, to investigate the contribution of CYP71A12 and its products to Arabidopsis immunity, we analyzed infection phenotypes of multiple mutant lines combining pen2 with pad3, cyp71A12, cyp71A13 or cyp82C2. Metabolite profiling of cyp71A12 lines revealed a reduction in ICA accumulation. Additionally, analysis of mutant plants showed that low amounts of ICA can form during an immune response by CYP71B6/AAO1-dependent metabolism of indole acetonitrile, but not via IG hydrolysis. Infection assays with Plectosphaerella cucumerina and Colletotrichum tropicale, two pathogens with different lifestyles, revealed cyp71A12-, cyp71A13- and cyp82C2-associated defects associated with Arabidopsis immunity. Our results indicate that CYP71A12, but not CYP71A13, is the major enzyme responsible for the accumulation of ICA in Arabidopsis in response to pathogen ingression. We also show that both enzymes are key players in the resistance of Arabidopsis against selected filamentous pathogens after they invade.