Cyanogenic glucosides and plant-insect interactions

Strawberry plant growth enhancement: Effects of artificial light and methyl jasmonate-salicylic acid treatments on physiology and metabolism

Strawberries, known for their antioxidant properties, exhibit changes in physiology and metabolite profiles based on cultivation techniques. In Indonesia, strawberries are typically grown in highland regions, but climate change has necessitated adjustments in cultivation practices to enhance production and quality. This study investigates the adaptation of strawberry plants in lowland environments using light-emitting diodes (LEDs) and the exogenous application of methyl jasmonate (MeJA) and methyl salicylic acid (MeSA). A randomized block design was used with two factors: LED light types and MeJA-MeSA treatments. While the treatments did not significantly affect shoot growth (initially 1.5-2 cm, increasing 3-5 times by day 3), chlorophyll content, or fruit sugar levels, notable effects were observed in leaf glucose accumulation. The control group showed a fivefold increase (0.55 μg ml-1), while LED-hormone treatments resulted in a 27-64 % lower increase (0.20-0.40 μg ml-1). Fructose levels followed a similar pattern, and malic acid content was highest in the MeJA treatment (5.76 mg ml-1), with MeSA treatments also enhancing malic acid (5.91 mg ml-1). The secondary metabolite analysis, conducted using GC-MS and LC-MS, identified key defense-related compounds, including terpenoids, saturated fats, alkaloids, and amino acid derivatives, which play a role in the plant's defense mechanisms. These findings highlight the potential of LED lighting and hormone applications to modulate strawberry physiology and suggest further research into their role in plant stress responses.

Evaluation of exposure to cyanogenic glycosides and potential hydrogen cyanide release in commercially available foods among the Korean population

The release of hydrogen cyanide (HCN) after food ingestion can pose a serious health risk to consumers. This study aimed to simultaneously quantify four cyanogenic glycosides (lotaustralin, prunasin, taxiphyllin, and dhurrin) using liquid chromatography-tandem mass spectrometry. The analysis scope extended beyond agricultural products to various consumer foods to estimate dietary exposure to cyanogenic glycosides and assess its risk levels. The major exposure sources are cassava chips (lotaustralin), apples (seeds) (prunasin and dhurrin), and Prunus mume axis (taxiphyllin). In addition to quantifying specific cyanogenic glycosides, this study proposed the development of a preliminary risk assessment framework based on the dietary exposure assessment and the calculation of theoretical levels of HCN derived from cyanogenic glycoside concentrations. In the absence of established guidelines for the permissible intake of foods containing cyanogenic glycosides, this study provides initial guidance for assessing the risks associated with a range of commonly consumed foods.

Functional characterization of Arabidopsis hydroxynitrile lyase in response to abiotic stress and the regulation of flowering time

BACKGROUND

Hydroxynitrile lyases (HNLs) are a class of hydrolytic enzymes from a wide range of sources, which play crucial roles in the catalysis of the reversible conversion of carbonyl compounds derived from cyanide and free cyanide in cyanogenic plant species. HNLs were also discovered in non-cyanogenic plants, such as Arabidopsis thaliana, and their roles remain unclear even during plant growth and reproduction.

METHODS AND RESULTS

The pattern of expression of the HNL in A. thaliana (AtHNL) in different tissues, as well as under abiotic stresses and hormone treatments, was examined by real-time quantitative reverse transcription PCR (qRT-PCR) and an AtHNL promoter-driven histochemical β-glucuronidase (GUS) assay. AtHNL is highly expressed in flowers and siliques, and the expression of AtHNL was dramatically affected by abiotic stresses and hormone treatments. The overexpression of AtHNL resulted in transgenic A. thaliana seedlings that were more tolerance to mannitol and salinity. Moreover, transgenic lines of A. thaliana that overexpressed this gene were less sensitive to abscisic acid (ABA). Altered expression of ABA/stress responsive genes was also observed in hnl mutant and AtHNL-overexpressing plants, suggesting AtHNL may play functional roles on regulating Arabidopsis resistance to ABA and abiotic stresses by affecting ABA/stress responsive gene expression. In addition, the overexpression of AtHNL resulted in earlier flowering, whereas the AtHNL mutant flowered later than the wild type (WT) plants. The expression of the floral stimulators CONSTANS (CO), SUPPRESSOR OF OVER EXPRESSION OF CO 1 (SOC1) and FLOWERING LOCUS T (FT) was upregulated in plants that overexpressed AtHNL when compared with the WT plants. In contrast, expression of the floral repressor FLOWERING LOCUS C (FLC) was upregulated in AtHNL mutants and downregulated in plants that overexpressed AtHNL compared to the WT plants.

CONCLUSION

This study revealed that AtHNL can be induced under abiotic stresses and ABA treatment, and genetic analysis showed that AtHNL could also act as a positive regulator of abiotic stress and ABA tolerance, as well as flowering time.

The Effect of One-Year Fermentation of Maesil Fruit (Prunus mume) Sugar Syrup on Amygdalin Level: A Natural Toxic Compound

Prunus mume (maesil) is an economically important fruit in Korea. Recently, public interest in maesil sugar syrup is increasing. However, the presence of toxic amygdalin in the fruit syrup is a concern. Thus, the current investigation aimed to observe effects of maesil maturity, ripening methods, processing, and fermentation period on the amygdalin level in maesil sugar syrup. Six different types of maesil sugar syrup were prepared and amygdalin content was monitored at 3-month intervals. Higher levels (>63 mg/L) of amygdalin were found in syrups prepared from unripe fruit compared to those in syrups made from ripe fruit after 3 months of fermentation. A rapid reduction in amygdalin content was observed until 9 months in all syrups, gradually reducing to <5 mg/L at 12 months. More than 9 months of maturation is crucial for reducing the amygdalin content maesil sugar syrup, regardless of fruit maturity, source of fruit, and processing method.

The Putative GATA Transcription Factor SbGATA22 as a Novel Regulator of Dhurrin Biosynthesis

Cyanogenic glucosides are specialized metabolites produced by over 3000 species of higher plants from more than 130 families. The deployment of cyanogenic glucosides is influenced by biotic and abiotic factors in addition to being developmentally regulated, consistent with their roles in plant defense and stress mitigation. Despite their ubiquity, very little is known regarding the molecular mechanisms that regulate their biosynthesis. The biosynthetic pathway of dhurrin, the cyanogenic glucoside found in the important cereal crop sorghum (Sorghum bicolor (L.) Moench), was described over 20 years ago, and yet no direct regulator of the biosynthetic genes has been identified. To isolate regulatory proteins that bind to the promoter region of the key dhurrin biosynthetic gene of sorghum, SbCYP79A1, yeast one-hybrid screens were performed. A bait fragment containing 1204 base pairs of the SbCYP79A1 5' regulatory region was cloned upstream of a reporter gene and introduced into Saccharomyces cerevisiae. Subsequently, the yeast was transformed with library cDNA representing RNA from two different sorghum developmental stages. From these screens, we identified SbGATA22, an LLM domain B-GATA transcription factor that binds to the putative GATA transcription factor binding motifs in the SbCYP79A1 promoter region. Transient assays in Nicotiana benthamiana show that SbGATA22 localizes to the nucleus. The expression of SbGATA22, in comparison with SbCYP79A1 expression and dhurrin concentration, was analyzed over 14 days of sorghum development and in response to nitrogen application, as these conditions are known to affect dhurrin levels. Collectively, these findings suggest that SbGATA22 may act as a negative regulator of SbCYP79A1 expression and provide a preliminary insight into the molecular regulation of dhurrin biosynthesis in sorghum.

Response of cassava (Manihot esculenta Crantz) genotypes to natural infestation by scale insect pest Stictococcus vayssierei Richard (Hemiptera: Stictococcidae)

Cassava is mostly grown for its starchy roots, which ensure food security. However, it is heavily attacked by the African root and tuber scale (ARTS) Stictococcus vayssierei in Central Africa. This pest is a severe constraint to the production of cassava, food and income security for smallholder farmers. Crop resistance development through the selection of varieties with resistant traits against targeted pests is a promising approach to pest control. This study investigated cassava genotypes' response to natural infestation and determined their resistance levels against S. vayssierei. Six cassava genotypes (two local and four improved) were planted in a completely randomized block design with four replicates. Agronomic parameters and ARTS density were evaluated at 3, 6, 9 and 12 months after planting (MAP). Biochemical content was determined on the pith and cortex of 12 MAP aged tuberous roots. As a result, the improved Excel variety recorded the highest scale density per plant with 102.83 ± 4.14 ARTS/P at 9 MAP. At 12 MAP, high activity of total cyanide (69.18 ± 0.88 and 69.16 ± 1.44 mg/kg) and phenylalanine ammonia-lyase (0.142 ± 0.020 and 0.145 ± 0.010 ΔA/min/mg) were observed in the cortex of the tuberous roots of the improved varieties TMS 96/0023 and TMS 92/0057 which were colonized by the lowest ARTS density. The local variety (Douma) had a high content of total phenols (44.87 ± 1.15 µg/g) in the pith. It also produced the highest yield (23.8 ± 2.9 t ha-1). Varieties TMS 96/0023, TMS 92/0057 and Douma may be the most suitable varieties for the control of ARTS stress.

Release of glycosidically-bound volatiles in orange juice under natural conditions

Glycosidically-bound volatiles (GBV) can be released by exogenous acid and enzymatic hydrolysis. However, the liberation of GBV in natural juice is not reported. It was found that part of the GBV in orange juice (OJ) under natural conditions can be released and the types of volatiles were considerably fewer than the ones under exogenous acid, or enzymatic hydrolysis. Seven types of aroma substances were released under endogenous enzyme, among which ethyl 3-hydroxyhexanoate and eugenol are characteristic aroma substances of OJ. Six kinds of aroma substances can be released under natural acidic conditions, none are characteristic aroma substances of OJ. Ten kinds of substances were released under endogenous enzymes in combination with the acidic condition, among which benzyl alcohol, ethyl 3-hydroxyhexanoate, citral, and eugenol are characteristic aroma substances of OJ. The results indicated that GBV may play an important role in resisting the decrease of free aroma in OJ during storage.

Old poisons, new signaling molecules: the case of hydrogen cyanide

The high phenotypic plasticity developed by plants includes rapid responses and adaptations to aggressive or changing environments. To achieve this, they evolved extremely efficient mechanisms of signaling mediated by a wide range of molecules, including small signal molecules. Among them, hydrogen cyanide (HCN) has been largely ignored due to its toxic characteristics. However, not only is it present in living organisms, but it has been shown that it serves several functions in all kingdoms of life. Research using model plants has changed the traditional point of view, and it has been demonstrated that HCN plays a positive role in the plant response to pathogens independently of its toxicity. Indeed, HCN induces a response aimed at protecting the plant from pathogen attack, and the HCN is provided either exogenously (in vitro or by some cyanogenic bacteria species present in the rhizosphere) or endogenously (in reactions involving ethylene, camalexin, or other cyanide-containing compounds). The contribution of different mechanisms to HCN function, including a new post-translational modification of cysteines in proteins, namely S-cyanylation, is discussed here. This work opens up an expanding 'HCN field' of research related to plants and other organisms.

Resequencing of global Lotus corniculatus accessions reveals population distribution and genetic loci, associated with cyanogenic glycosides accumulation and growth traits

BACKGROUND

Lotus corniculatus is a widely distributed perennial legume whose great adaptability to different environments and resistance to barrenness make it an excellent forage and ecological restoration plant. However, its molecular genetics and genomic relationships among populations are yet to be uncovered.

RESULT

Here we report on a genomic variation map from worldwide 272 L. corniculatus accessions by genome resequencing. Our analysis suggests that L. corniculatus accessions have high genetic diversity and could be further divided into three subgroups, with the genetic diversity centers were located in Transcaucasia. Several candidate genes and SNP site associated with CNglcs content and growth traits were identified by genome-wide associated study (GWAS). A non-synonymous in LjMTR was responsible for the decreased expression of CNglcs synthesis genes and LjZCD was verified to positively regulate CNglcs synthesis gene CYP79D3. The LjZCB and an SNP in LjZCA promoter were confirmed to be involved in plant growth.

CONCLUSION

This study provided a large number of genomic resources and described genetic relationship and population structure among different accessions. Moreover, we attempt to provide insights into the molecular studies and breeding of CNglcs and growth traits in L. corniculatus.

Transcriptomic Responses of Salvia hispanica to the Infestation of Red Spider Mites (Tetranychus neocaledonicus)

Salvia hispanica (chia) is a highly nutritious food source and has gained popularity due to its high omega-3 fatty acid content. Red spider mites are a serious problem in the production of S. hispanica. However, no study has been conducted to analyze the defensive response to the infestation of red spider mites in S. hispanica. To elucidate the molecular mechanisms of the defensive response of S. hispanica to red spider mites, we performed a transcriptomic analysis of S. hispanica when infested by red spider mites. In the comparative assessment of leaf transcriptomes, a total of 1743 differentially expressed genes (DEGs) were identified between control and mite-infested S. hispanica. From these, 1208 (69%) transcripts were upregulated and 535 (31%) were downregulated. The DEGs included transcription factors, defense hormones, and secondary metabolites that were either suppressed or activated in response to spider mite herbivory. Gene Ontology (GO) enrichment analysis revealed that plant secondary metabolites, such as glucosinolates, and signaling pathways, including the jasmonic acid signaling pathway, may play an important role in the defense against red spider mites. This study provides novel insights into the defense response of S. hispanica to insect herbivory and could be a resource for the improvement of pest resistance in the chia.

Dietary Challenges for Parasitoid Wasps (Hymenoptera: Ichneumonoidea); Coping with Toxic Hosts, or Not?

Many insects defend themselves against predation by being distasteful or toxic. The chemicals involved may be sequestered from their diet or synthesized de novo in the insects' body tissues. Parasitoid wasps are a diverse group of insects that play a critical role in regulating their host insect populations such as lepidopteran caterpillars. The successful parasitization of caterpillars by parasitoid wasps is contingent upon their aptitude for locating and selecting suitable hosts, thereby determining their efficacy in parasitism. However, some hosts can be toxic to parasitoid wasps, which can pose challenges to their survival and reproduction. Caterpillars employ a varied array of defensive mechanisms to safeguard themselves against natural predators, particularly parasitoid wasps. These defenses are deployed pre-emptively, concurrently, or subsequently during encounters with such natural enemies. Caterpillars utilize a range of strategies to evade detection or deter and evade attackers. These tactics encompass both measures to prevent being noticed and mechanisms aimed at repelling or eluding potential threats. Post-attack strategies aim to eliminate or incapacitate the eggs or larvae of parasitoids. In this review, we investigate the dietary challenges faced by parasitoid wasps when encountering toxic hosts. We first summarize the known mechanisms through which insect hosts can be toxic to parasitoids and which protect caterpillars from parasitization. We then discuss the dietary adaptations and physiological mechanisms that parasitoid wasps have evolved to overcome these challenges, such as changes in feeding behavior, detoxification enzymes, and immune responses. We present new analyses of all published parasitoid-host records for the Ichneumonoidea that attack Lepidoptera caterpillars and show that classically toxic host groups are indeed hosts to significantly fewer species of parasitoid than most other lepidopteran groups.

Adaptive Changes in Detoxification Metabolism and Transmembrane Transport of Bombyx mori Malpighian Tubules to Artificial Diet

The high adaptability of insects to food sources has contributed to their ranking among the most abundant and diverse species on Earth. However, the molecular mechanisms underlying the rapid adaptation of insects to different foods remain unclear. We explored the changes in gene expression and metabolic composition of the Malpighian tubules as an important metabolic excretion and detoxification organ in silkworms (Bombyx mori) fed mulberry leaf and artificial diets. A total of 2436 differentially expressed genes (DEGs) and 245 differential metabolites were identified between groups, with the majority of DEGs associated with metabolic detoxification, transmembrane transport, and mitochondrial function. Detoxification enzymes, such as cytochrome P450 (CYP), glutathione-S-transferase (GST), and UDP-glycosyltransferase, and ABC and SLC transporters of endogenous and exogenous solutes were more abundant in the artificial diet group. Enzyme activity assays confirmed increased CYP and GST activity in the Malpighian tubules of the artificial diet-fed group. Metabolome analysis showed increased contents of secondary metabolites, terpenoids, flavonoids, alkaloids, organic acids, lipids, and food additives in the artificial diet group. Our findings highlight the important role of the Malpighian tubules in adaptation to different foods and provide guidance for further optimization of artificial diets to improve silkworm breeding.

Metabolic consequences of various fruit-based diets in a generalist insect species

Most phytophagous insect species exhibit a limited diet breadth and specialize on a few or a single host plant. In contrast, some species display a remarkably large diet breadth, with host plants spanning several families and many species. It is unclear, however, whether this phylogenetic generalism is supported by a generic metabolic use of common host chemical compounds ('metabolic generalism') or alternatively by distinct uses of diet-specific compounds ('multi-host metabolic specialism')? Here, we simultaneously investigated the metabolomes of fruit diets and of individuals of a generalist phytophagous species, Drosophila suzukii, that developed on them. The direct comparison of metabolomes of diets and consumers enabled us to disentangle the metabolic fate of common and rarer dietary compounds. We showed that the consumption of biochemically dissimilar diets resulted in a canalized, generic response from generalist individuals, consistent with the metabolic generalism hypothesis. We also showed that many diet-specific metabolites, such as those related to the particular color, odor, or taste of diets, were not metabolized, and rather accumulated in consumer individuals, even when probably detrimental to fitness. As a result, while individuals were mostly similar across diets, the detection of their particular diet was straightforward. Our study thus supports the view that dietary generalism may emerge from a passive, opportunistic use of various resources, contrary to more widespread views of an active role of adaptation in this process. Such a passive stance towards dietary chemicals, probably costly in the short term, might favor the later evolution of new diet specializations.

Genome-wide identification of UDP-glycosyltransferases in the tea plant (Camellia sinensis) and their biochemical and physiological functions

Tea (Camellia sinensis) has been an immensely important commercially grown crop for decades. This is due to the presence of essential nutrients and plant secondary metabolites that exhibit beneficial health effects. UDP-glycosyltransferases (UGTs) play an important role in the diversity of such secondary metabolites by catalysing the transfer of an activated sugar donor to acceptor molecules, and thereby creating a huge variety of glycoconjugates. Only in recent years, thanks to the sequencing of the tea plant genome, have there been increased efforts to characterise the UGTs in C. sinensis to gain an understanding of their physiological role and biotechnological potential. Based on the conserved plant secondary product glycosyltransferase (PSPG) motif and the catalytically active histidine in the active site, UGTs of family 1 in C. sinensis are identified here, and shown to cluster into 21 groups in a phylogenetic tree. Building on this, our current understanding of recently characterised C. sinensis UGTs (CsUGTs) is highlighted and a discussion on future perspectives made.

Cyanogenesis, a Plant Defence Strategy against Herbivores

Plants and phytophagous arthropods have coevolved in a long battle for survival. Plants respond to phytophagous feeders by producing a battery of antiherbivore chemical defences, while herbivores try to adapt to their hosts by attenuating the toxic effect of the defence compounds. Cyanogenic glucosides are a widespread group of defence chemicals that come from cyanogenic plants. Among the non-cyanogenic ones, the Brassicaceae family has evolved an alternative cyanogenic pathway to produce cyanohydrin as a way to expand defences. When a plant tissue is disrupted by an herbivore attack, cyanogenic substrates are brought into contact with degrading enzymes that cause the release of toxic hydrogen cyanide and derived carbonyl compounds. In this review, we focus our attention on the plant metabolic pathways linked to cyanogenesis to generate cyanide. It also highlights the role of cyanogenesis as a key defence mechanism of plants to fight against herbivore arthropods, and we discuss the potential of cyanogenesis-derived molecules as alternative strategies for pest control.

The role of cyanoalanine synthase and alternative oxidase in promoting salt stress tolerance in Arabidopsis thaliana

BACKGROUND

Cyanide is a toxic chemical that inhibits cellular respiration. In plants, cyanide can be produced by themselves, especially under stressful conditions. Cyanoalanine synthase (CAS) is a key enzyme involved in plant cyanide detoxification. There are three genes encoding CAS in Arabidopsis thaliana, but the roles of these genes in the plant's response to stress are less studied. In addition, it is known that alternative oxidase (AOX) mediates cyanide-resistant respiration, but the relationship between CAS and AOX in regulating the plant stress response remains largely unknown.

RESULTS

Here, the effects of the overexpression or mutation of these three CAS genes on salt stress tolerance were investigated. The results showed that under normal conditions, the overexpression or mutation of the CAS genes had no significant effect on the seed germination and growth of Arabidopsis thaliana compared with wild type (WT). However, under 50, 100, and 200 mM NaCl conditions, the seeds overexpressing CAS genes showed stronger salt stress resistance, i.e., higher germination speed than WT seeds, especially those that overexpressed the CYS-C1 and CYS-D1 genes. In contrast, the seeds with CAS gene mutations exhibited salt sensitivity, and their germination ability and growth were significantly damaged by 100 and 200 mM NaCl. Importantly, this difference in salt stress resistance became more pronounced in CAS-OE, WT, and mutant seeds with increasing salt concentration. The CAS-OE seeds maintained higher respiration rates than the WT and CAS mutant seeds under salt stress conditions. The cyanide contents in CAS mutant seeds were approximately 3 times higher than those in WT seeds and more than 5 times higher than those in CAS-OE seeds. In comparison, plants overexpressing CYS-C1 had the fastest detoxification of cyanide and the best salt tolerance, followed by those overexpressing CYS-D1 and CYS-D2. Furthermore, less hydrogen sulfide (H₂S) was observed in CAS-OE seedlings than in WT seedlings under long-term salt stress conditions. Nonetheless, the lack of AOX impaired CAS-OE-mediated plant salt stress resistance, suggesting that CAS and AOX interact to improve salt tolerance is essential. The results also showed that CAS and AOX contributed to the reduction in oxidative damage by helping maintain relatively high levels of antioxidant enzyme activity.

CONCLUSION

In summary, the findings of the present study suggest that overexpression of Arabidopsis CAS family genes plays a positive role in salt stress tolerance and highlights the contribution of AOX to CAS-mediated plant salt resistance, mainly by reducing cyanide and H₂S toxicity.

Onco-immunity and therapeutic application of amygdalin: A review

Background

Amygdalin is known as a chemical compound derived from various fruits. The glycosides existing in this plant have been historically utilized as an anticancer agent. This review presented an overview of amygdalin and its onco-immunity and other therapeutic medical applications.

Method

A literature search for studies relating to amygdalin and cancer treatment was carried out using PubMed and Google Scholar. Combinations of the following terms were used in the search strategies: "amygdalin," "rhodanese," "cyanide," "cyanogenic," "hypothiocyanite," "mandelonitrile," "glucosides," "cancer," "apoptosis," and "cytotoxicity," combined with a cancer term such as "seed," "almond," or "apricot," "cancer + cell line, antiproliferation or inhibition," "BAX From the March 3, 1981 until the April 15, 2021, all of the English-language papers were evaluated based on the inclusion criteria. Publications included reviews, chapters from books, and original research papers.

Results

The FDA prohibits Amygdalin from medical usage as an anticancer treatment due to a lack of proof of cure in cancer cases. When this natural-based compound is used with conditional chemotherapeutic medicines causes synergistic effects. Besides, amygdalin is used to manage asthma, improve the immune system, induce apoptosis in human renal fibroblasts, and inhibit hyperglycemia.

Conclusion

Various medical uses of amygdalin have been found such as managing asthma, improving the immune system, inducing apoptosis in human renal fibroblasts, and inhibiting hyperglycemia. More effective in vitro and review studies are required to elucidate the exact role of this herb in medical applications.

Dhurrin: A naturally occurring phytochemical as a weapon against insect herbivores

Dhurrin, a cyanogenic glucoside, is a plant defensive chemical synthesized from aliphatic amino acids and consists of β-d-glucopyranose linked to α-hydroxy nitrile. It is catabolized by the consecutive action of hydroxynitrilase and β-glucosidase to release hydrogen cyanide on tissue disruption during herbivory. These phytoanticipins are widely distributed across various monocot and dicot plants such as Sorghum, Macadamia, Ostrya sp., and many other plant species with ornamental, pharmaceutical, medicinal, and food value. Although repellent properties of dhurrin against herbivores are often reported, less is known about its distribution, metabolism, mode of action against insects, and application for pest control. Herein, we highlight recent updates on dhurrin distribution, biosynthesis, and catabolism along with the cyanide detoxification pathway. Additionally, this article focuses on biological activities of dhurrin against various herbivores and opportunities to explore the utilization of dhurrin as a natural pest control agent and a substitute for chemically synthesized pesticides.

Antibody-Based Methods Reveal the Protein Expression Properties of Glucosinolate Sulfatase 1 and 2 in Plutella xylostella

The glucosinolates (GLs) and myrosinase defensive systems in cruciferous plants were circumvented by Plutella xylostella using glucosinolate sulfatases (PxGSSs) during pest-plant interaction. Despite identifying three duplicated GSS-encoding genes in P. xylostella, limited information regarding their spatiotemporal and induced expression is available. Here, we investigated the tissue- and stage-specific expression and induction in response to GLs of PxGSS1 and PxGSS2 (PxGSS1/2) at the protein level, which shares a high degree of similarity in protein sequences. Western blotting (WB) analysis showed that PxGSS1/2 exhibited a higher protein level in mature larvae, their guts, and gut content. A significantly high protein and transcript levels of PxGSS1/2 were also detected in the salivary glands using WB and qRT-PCR. The immunofluorescence (IF) and immunohistochemistry (IHC) results confirmed that PxGSS1/2 is widely expressed in the larval body. The IHC was more appropriate than IF when autofluorescence interference was present in collected samples. Furthermore, the content of PxGSS1/2 did not change significantly under treatments of GL mixture from Arabidopsis thaliana ecotype Col-0, or commercial ally (sinigrin), 4-(methylsulfinyl)butyl, 3-(methylsulfinyl)propyl, and indol-3-ylmethyl GLs indicating that the major GLs from leaves of A. thaliana Col-0 failed to induce the expression of proteins for both PxGSS1 and PxGSS2. Our study systemically characterized the expression properties of PxGSS1/2 at the protein level, which improves our understanding of PxGSS1/2-center adaptation in P. xylostella during long-term insect-plant interaction.

An inducible gene from glycoside hydrolase one family of Plutella xylostella decreases larval survival when feeding on host plant

Glycoside hydrolase family 1 (GH1) members exhibit a broad substrate spectrum and play important roles in insect-plant interactions, such as the defensive β-glucosidase and β-thioglucosidase (so-called myrosinase). However, knowledge about the expression profiling and function of glycoside hydrolase family 1 members in a specialist pest of crucifers Plutella xylostella is still limited. In this study, 13 putative glycoside hydrolase family 1 members of P. xylostella were identified based on the sequence characteristics, while no myrosinase activity was detectable in P. xylostella using gas chromatography-mass spectrometry (GC-MS). Expression profiling of these glycoside hydrolase family 1 members identified the midgut-specific gene Px008848 that is induced by host plant. Further experiments revealed that the in vitro expressed Px008848 protein had β-glucosidase activity and the survival rate of the larvae feeding on wounded Arabidopsis thaliana leaves declined when leaves were treated with purified Px008848 protein. When CRISPR/Cas9-based homozygous mutant larvae of Px008848 and wild-type larvae were respectively transferred onto the A. thaliana, the larval survival rate of the mutant larvae was significantly higher than that of the wild-type individuals. Our work showed that certain insect glycoside hydrolase family 1 gene may have negative effect on the development of larvae feeding on the host plant, which broadened our understandings on the evolutionary function of this gene family in the insect-plant interaction.

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.

Effect of a short-cycle apple tree cultivar on oriental fruit moth (Lepidoptera: Tortricidae) development and larval behavior

The oriental fruit moth, Grapholita molesta (Busch, 1916) has historically been a major problem in traditional apple-growing regions in Rio Grande do Sul and Santa Catarina; however, a lower occurrence of G. molesta has been observed in early variety ('Eva') than long cycles cultivar 'Gala' in Paraná State. The objective of this study was to evaluate the performance of immature and adult G. molesta in apple cultivars with short and long cycles, in addition to elucidating whether there is adaptive potential for development and fertility from the first generation to the fourth. The experimental treatments consisted of larvae fed 'Eva' and 'Gala' fruit and a commercial diet. Immature development time, head capsule width, longevity and reproductive parameters were compared across the treatments. The larvae of the fourth generation exhibited better performance than those of the first on 'Eva' and 'Gala'. Immature oriental fruit moth development occurred via four or five instars. A greater number of larvae with four instars occurred on 'Eva' than on 'Gala'. The head capsule width was narrower on 'Gala' than on 'Eva' for larvae with four instars. Females reared on 'Eva' also laid more eggs than those reared on 'Gala'. The larvae that were more adapted to the feeding conditions showed reduced cycles/instars, and the females exhibited better performance when new generations originated from the same substrate. The high fluctuation of G. molesta in 'Gala' orchards is not due to the nutritional condition of the fruits.

A Comparative Analysis of Bombyx mori (Lepidoptera: Bombycidae) β-fructofuranosidase Homologs Reveals Different Post-Translational Regulations in Glyphodes pyloalis Walker (Lepidoptera: Pyralidae)

Simple Summary

The β-fructofuranosidase (β-FFase) encoding gene BmSuc1 regulates the glycometabolism of silkworm larvae, and it participates in the resistance of mulberry alkaloids. However, there is no molecular or biochemical information available about the mulberry pest Glyphodespyloalis Walker β-FFase homologs. In this paper, we have obtained five β-FFase homologous genes in G. pyloalis and characterized the expression and the localization of GpSUC1a in the midgut. The β-FFase activity in the midgut of G. pyloalis larvae and GpSUC1a were both confirmed, while recombinant GpSUC1a displayed little activity as compared with the higher activity of BmSUC1. Some putative N-glycosylation sites were found in GpSUC1a but none in BmSUC1, while there was more methylation in BmSUC1 than in GpSUC1a. The results indicate that such post-translational modifications (PTMs) are differentially supporting that β-FFase are active in these two mulberry feeding caterpillars, and the activation of GpSUC1a may be controlled by a more complex post-translational regulatory system in G. pyloalis larvae. This is the first report on the characterization of β-FFase genes from G. pyloalis and the first comparison of expression regulation between two mulberry feeding insects B. mori and G. pyloalis. Moreover, this research may provide new ideas for the management of mulberry borers.

Abstract

The silk-spinning and Lepidopteran model insect Bombyx mori (Bombycidae) is a mulberry specialist. The BmSuc1 gene is the first β-fructofuranosidase (β-FFase) encoding gene identified in animals, and β-FFase acts as an essential sucrase for glycometabolism modulation in the silkworm larvae, involved in resistance to mulberry alkaloids. Glyphodes pyloalis Walker (Lepidoptera: Pyralidae) is an important mulberry pest leading to heavy economic loss of sericulture. However, no molecular or biochemical information is available about G. pyloalis β-FFase homologs. In this study, five β-FFase homologous genes in G. pyloalis were obtained. The genes GpSuc1a and GpSuc2c were expressed in the midgut; GpSuc2c encodes a truncated polypeptide. The expression and the localization of GpSUC1a in the midgut was characterized. Whereas recombinant GpSUC1a expressed in both Escherichia coli and BmN cells displayed little activity as compared with higher activity of BmSUC1, β-FFase activity in the larval midgut of G. pyloalis and GpSUC1a purified from the midgut were both confirmed. The data suggested that the activation of GpSUC1a is probably controlled by a more complicated post-translational regulation system in G. pyloalis larvae than that of BmSUC1 in B. mori. To study post-translational modifications (PTMs), GpSUC1a and BmSUC1 were purified from larval midguts using immunoprecipitation and subjected to LC-MS to perform PTMs analysis. Some putative N-glycosylated sites were found in GpSUC1a but none in BmSUC1, while there was more methylation in BmSUC1 than in GpSUC1a, indicating that such PTMs were supporting the differential β-FFases activities in these two mulberry feeding caterpillars.

Insights Into the Properties of Amygdalin Solvatomorphs: X-ray Structures, Intermolecular Interactions, and Transformations

Amygdalin is an effective component of the traditional Chinese medicine bitter almond, peach kernel, and plum kernel. It has pharmacological effects, such as relieving cough and asthma. In a study of the crystallization process, we found a series of solvatomorphs of amygdalin (including hydrate). Interestingly, in the structures of these solvatomorphs, the same characteristic structural fragment is present, that is, amygdalin dihydrate. Multiple analytical techniques were used to characterize the solvatomorphs, such as X-ray diffraction and thermogravimetry-mass spectrometry. Void calculations of water and solvent were used to analyze the occupied volume in the unit cell of the corresponding solvatomorphs to explain the formation mechanism of the solvatomorphs from the perspective of space. To elucidate the formation mechanism of the solvatomorphs with this kind of characteristic structure from the perspective of energy, theoretical calculations based on density functional theory were applied, such as energy decomposition and molecular electrostatic potential surfaces. In addition, the transformation phenomenon between these solvatomorphs and amygdalin was identified, and the transformation pathways are described in detail.

Seedling growth and fall armyworm feeding preference influenced by dhurrin production in sorghum

Cyanogenic glucosides (CGs) play a key role in host-plant defense to insect feeding; however, the metabolic tradeoffs between synthesis of CGs and plant growth are not well understood. In this study, genetic mutants coupled with nondestructive phenotyping techniques were used to study the impact of the CG dhurrin on fall armyworm [Spodoptera frugiperda (J.E. Smith)] (FAW) feeding and plant growth in sorghum [Sorghum bicolor (L.) Moench]. A genetic mutation in CYP79A1 gene that disrupts dhurrin biosynthesis was used to develop sets of near-isogenic lines (NILs) with contrasting dhurrin contents in the Tx623 bmr6 genetic background. The NILs were evaluated for differences in plant growth and FAW feeding damage in replicated greenhouse and field trials. Greenhouse studies showed that dhurrin-free Tx623 bmr6 cyp79a1 plants grew more quickly than wild-type plants but were more susceptible to insect feeding based on changes in green plant area (GPA), total leaf area, and total dry weight over time. The NILs exhibited similar patterns of growth in field trials with significant differences in leaf area and dry weight of dhurrin-free plants between the infested and non-infested treatments. Taken together, these studies reveal a significant metabolic tradeoff between CG biosynthesis and plant growth in sorghum seedlings. Disruption of dhurrin biosynthesis produces plants with higher growth rates than wild-type plants but these plants have greater susceptibility to FAW feeding.

Seedling growth and fall armyworm feeding preference influenced by dhurrin production in sorghum

Cyanogenic glucosides (CGs) play a key role in host-plant defense to insect feeding; however, the metabolic tradeoffs between synthesis of CGs and plant growth are not well understood. In this study, genetic mutants coupled with nondestructive phenotyping techniques were used to study the impact of the CG dhurrin on fall armyworm [Spodoptera frugiperda (J.E. Smith)] (FAW) feeding and plant growth in sorghum [Sorghum bicolor (L.) Moench]. A genetic mutation in CYP79A1 gene that disrupts dhurrin biosynthesis was used to develop sets of near-isogenic lines (NILs) with contrasting dhurrin contents in the Tx623 bmr6 genetic background. The NILs were evaluated for differences in plant growth and FAW feeding damage in replicated greenhouse and field trials. Greenhouse studies showed that dhurrin-free Tx623 bmr6 cyp79a1 plants grew more quickly than wild-type plants but were more susceptible to insect feeding based on changes in green plant area (GPA), total leaf area, and total dry weight over time. The NILs exhibited similar patterns of growth in field trials with significant differences in leaf area and dry weight of dhurrin-free plants between the infested and non-infested treatments. Taken together, these studies reveal a significant metabolic tradeoff between CG biosynthesis and plant growth in sorghum seedlings. Disruption of dhurrin biosynthesis produces plants with higher growth rates than wild-type plants but these plants have greater susceptibility to FAW feeding.

Transcript profiles of wild and domesticated sorghum under water-stressed conditions and the differential impact on dhurrin metabolism

MAIN CONCLUSION

Australian native species of sorghum contain negligible amounts of dhurrin in their leaves and the cyanogenesis process is regulated differently under water-stress in comparison to domesticated sorghum species. Cyanogenesis in forage sorghum is a major concern in agriculture as the leaves of domesticated sorghum are potentially toxic to livestock, especially at times of drought which induces increased production of the cyanogenic glucoside dhurrin. The wild sorghum species endemic to Australia have a negligible content of dhurrin in the above ground tissues and thus represent a potential resource for key agricultural traits like low toxicity. In this study we investigated the differential expression of cyanogenesis related genes in the leaf tissue of the domesticated species Sorghum bicolor and the Australian native wild species Sorghum macrospermum grown in glasshouse-controlled water-stress conditions using RNA-Seq analysis to analyse gene expression. The study identified genes, including those in the cyanogenesis pathway, that were differentially regulated in response to water-stress in domesticated and wild sorghum. In the domesticated sorghum, dhurrin content was significantly higher compared to that in the wild sorghum and increased with stress and decreased with age whereas in wild sorghum the dhurrin content remained negligible. The key genes in dhurrin biosynthesis, CYP79A1, CYP71E1 and UGT85B1, were shown to be highly expressed in S. bicolor. DHR and HNL encoding the dhurrinase and α-hydroxynitrilase catalysing bio-activation of dhurrin were also highly expressed in S. bicolor. Analysis of the differences in expression of cyanogenesis related genes between domesticated and wild sorghum species may allow the use of these genetic resources to produce more acyanogenic varieties in the future.

Effect of cyanide ions (CN-) extracted from cassava (Manihotesculenta Crantz) on Alveolar Epithelial Cells (A549 cells)

Cassava (Manihotesculenta Crantz) is one of the most important root crops in tropical countries. It is a major source of cyanogenic glycosides viz. linamarin and lotaustralin, and these on breakdown liberate HCN and ketone. Cassava cyanide extract (CCE) from cassava leaves and tuber rinds were formulated as a biopesticide against certain borer insect pests of horticultural crops. Adenocarcinomic human alveolar basal epithelial cells (A549) were treated with three different concentrations (100, 200, 400 ppm) of CCE. The MTT and NRU assays showed dose-dependent cytotoxicity. The DCFH-DA assay does not show any free radical scavenging activity, whereas the NRR assay showed a reduction in the nitrile radicals with an increase in the concentration of the bioactive compound. A negative correlation was found between the concentration of the bioactive principles and mitochondrial and lysosomal functions. Various cellular assays demonstrated the cellular response of the CCE, and it was found that at higher concentration (400 ppm), the CCE exert a significant necrotic cell death rather than apoptosis. The results of the study indicated that the CCE have a remarkable tendency of anti-proliferative ability.

Cascading Effects of Root Microbial Symbiosis on the Development and Metabolome of the Insect Herbivore Manduca sexta L

Root mutualistic microbes can modulate the production of plant secondary metabolites affecting plant-herbivore interactions. Still, the main mechanisms underlying the impact of root mutualists on herbivore performance remain ambiguous. In particular, little is known about how changes in the plant metabolome induced by root mutualists affect the insect metabolome and post-larval development. By using bioassays with tomato plants (Solanum lycopersicum), we analyzed the impact of the arbuscular mycorrhizal fungus Rhizophagus irregularis and the growth-promoting fungus Trichoderma harzianum on the plant interaction with the specialist insect herbivore Manduca sexta. We found that root colonization by the mutualistic microbes impaired insect development, including metamorphosis. By using untargeted metabolomics, we found that root colonization by the mutualistic microbes altered the secondary metabolism of tomato shoots, leading to enhanced levels of steroidal glycoalkaloids. Untargeted metabolomics further revealed that root colonization by the mutualists affected the metabolome of the herbivore, leading to an enhanced accumulation of steroidal glycoalkaloids and altered patterns of fatty acid amides and carnitine-derived metabolites. Our results indicate that the changes in the shoot metabolome triggered by root mutualistic microbes can cascade up altering the metabolome of the insects feeding on the colonized plants, thus affecting the insect development.

A proteomic approach to identify digestive enzymes, their exocytic and microapocrine secretory routes and their compartmentalization in the midgut of Spodoptera frugiperda

A proteomic approach was used to identify the digestive enzymes secreted by exocytosis and by microapocrine vesicles and enzyme midgut compartmentalization in Spodoptera frugiperda larvae. For this, proteomic analyses were performed in isolated midgut enterocyte microvillar membrane, in a fraction enriched in microapocrine vesicles (separated in soluble and membrane fractions), in the washings of the peritrophic membrane to isolate its loosely- and tightly-bound proteins, and in the peritrophic membrane contents. PM washings correspond to proteins extracted from the mucus layer surrounding PM. Serine endopeptidases (trypsins, chymotrypsins and serine endopeptidase homologs that have substitutions in the catalytic residues) and lipases are mainly secreted by exocytosis. Aminopeptidases are mainly microvillar enzymes and some are secreted membrane-bound to microapocrine vesicles, whereas carboxypeptidase isoforms follow different secretory routes. The results also showed that most polymer hydrolases (such as amylase and endopeptidases) are not retained in the ectoperitrophic fluid (found in PM washings but absent from PM contents). On the contrary, most enzymes involved in intermediate digestion (exemplified by carboxypeptidase and aminopeptidase) do not pass through the peritrophic membrane. Finally, the data revealed that the protein composition of PM includes peritrophins classified as peritrophic membrane proteins, PMP, and chitin deacetylase.

Phytochemistry reflects different evolutionary history in traditional classes versus specialized structural motifs

Foundational hypotheses addressing plant-insect codiversification and plant defense theory typically assume a macroevolutionary pattern whereby closely related plants have similar chemical profiles. However, numerous studies have documented variation in the degree of phytochemical trait lability, raising the possibility that phytochemical evolution is more nuanced than initially assumed. We utilize proton nuclear magnetic resonance (1H NMR) data, chemical classification, and double digest restriction-site associated DNA sequencing (ddRADseq) to resolve evolutionary relationships and characterize the evolution of secondary chemistry in the Neotropical plant clade Radula (Piper; Piperaceae). Sequencing data substantially improved phylogenetic resolution relative to past studies, and spectroscopic characterization revealed the presence of 35 metabolite classes. Metabolite classes displayed phylogenetic signal, whereas the crude 1H NMR spectra featured little evidence of phylogenetic signal in multivariate tests of chemical resonances. Evolutionary correlations were detected in two pairs of compound classes (flavonoids with chalcones; p-alkenyl phenols with kavalactones), where the gain or loss of a class was dependent on the other's state. Overall, the evolution of secondary chemistry in Radula is characterized by strong phylogenetic signal of traditional compound classes and weak phylogenetic signal of specialized chemical motifs, consistent with both classic evolutionary hypotheses and recent examinations of phytochemical evolution in young lineages.

Phenolic substances and cyanogenesis in galled and non-galled tissue of the fern species Microgramma vacciniifolia

Galls, neo-formed plant structures that can occur in different organs, are generated by species-specific interaction with an inducing organism. Inducers manipulate the metabolism of its host. Microgramma vacciniifolia (Langsd. & Fisch.) Copel. is a Neotropical epiphytic fern that hosted two stem galls, one induced by a midge species (Diptera) and other by a micromoth species (Lepidoptera). The aim of this study was to evaluate the impact of these two gall-inducing insects on the biochemistry of phenolic acids and the cyanogenesis in galls, stems and leaves of M. vacciniifolia. High performance liquid chromatography (HPLC) indicated a total of 14 phenol derivatives, including caffeic and coumaric acid. Principal Coordinates Analysis (PCoA) of the phenolic substances indicated three groups consisting (1) non-galled stems and micromoth-induced galls; (2) midge-induced galls; (3) midge-induced galls with parasitoids. Regarding the frequency of cyanogenesis assessed by the picrate paper test, the chi-squared test showed significant difference between fertile leaves (8.3%), sterile leaves (27.7%), non-galled stems (0%) and galls. Among galls, only the midge-induced galls analyzed were cyanogenic (15%). Our results indicated that the different gall-inducers (midge and micromoth) promote species-specific alterations to the phenolic substance composition of the host fern.

Amygdalin: Toxicity, Anticancer Activity and Analytical Procedures for Its Determination in Plant Seeds

Amygdalin (d-Mandelonitrile 6-O-β-d-glucosido-β-d-glucoside) is a natural cyanogenic glycoside occurring in the seeds of some edible plants, such as bitter almonds and peaches. It is a medically interesting but controversial compound as it has anticancer activity on one hand and can be toxic via enzymatic degradation and production of hydrogen cyanide on the other hand. Despite numerous contributions on cancer cell lines, the clinical evidence for the anticancer activity of amygdalin is not fully confirmed. Moreover, high dose exposures to amygdalin can produce cyanide toxicity. The aim of this review is to present the current state of knowledge on the sources, toxicity and anticancer properties of amygdalin, and analytical methods for its determination in plant seeds.

Cyanogenic Glycoside Analysis in American Elderberry

Cyanogenic glycosides (CNGs) are naturally occurring plant molecules (nitrogenous plant secondary metabolites) which consist of an aglycone and a sugar moiety. Hydrogen cyanide (HCN) is released from these compounds following enzymatic hydrolysis causing potential toxicity issues. The presence of CNGs in American elderberry (AE) fruit, Sambucus nigra (subsp. canadensis), is uncertain. A sensitive, reproducible and robust LC-MS/MS method was developed and optimized for accurate identification and quantification of the intact glycoside. A complimentary picrate paper test method was modified to determine the total cyanogenic potential (TCP). TCP analysis was performed using a camera-phone and UV-Vis spectrophotometry. A method validation was conducted and the developed methods were successfully applied to the assessment of TCP and quantification of intact CNGs in different tissues of AE samples. Results showed no quantifiable trace of CNGs in commercial AE juice. Levels of CNGs found in various fruit tissues of AE cultivars studied ranged from between 0.12 and 6.38 µg/g. In pressed juice samples, the concentration range measured was 0.29-2.36 µg/mL and in seeds the levels were 0.12-2.38 µg/g. TCP was highest in the stems and green berries. Concentration levels in all tissues were generally low and at a level that poses no threat to consumers of fresh and processed AE products.

Large-scale genome-wide association study, using historical data, identifies conserved genetic architecture of cyanogenic glucoside content in cassava (Manihot esculenta Crantz) root

Manihot esculenta (cassava) is a root crop originating from South America that is a major staple in the tropics, including in marginal environments. This study focused on South American and African germplasm and investigated the genetic architecture of hydrogen cyanide (HCN), a major component of root quality. HCN, representing total cyanogenic glucosides, is a plant defense component against herbivory but is also toxic for human consumption. We genotyped 3354 landraces and modern breeding lines originating from 26 Brazilian states and 1389 individuals were phenotypically characterized across multi-year trials for HCN. All plant material was subjected to high-density genotyping using genotyping by sequencing. We performed genome-wide association mapping to characterize the genetic architecture and gene mapping of HCN. Field experiments revealed strong broad- and narrow-sense trait heritability (0.82 and 0.41, respectively). Two major loci were identified, encoding for an ATPase and a MATE protein, and contributing up to 7 and 30% of the HCN concentration in roots, respectively. We developed diagnostic markers for breeding applications, validated trait architecture consistency in African germplasm and investigated further evidence for the domestication of sweet and bitter cassava. Fine genomic characterization revealed: (i) the major role played by vacuolar transporters in regulating HCN content; (ii) the co-domestication of sweet and bitter cassava major alleles are dependent upon geographical zone; and (iii) the major loci allele for high HCN in M. esculenta Crantz seems to originate from its ancestor, M. esculenta subsp. flabellifolia. Taken together, these findings expand our insights into cyanogenic glucosides in cassava roots and its glycosylated derivatives in plants.

Metabolomic Study of Sorghum (Sorghum bicolor) to Interpret Plant Behavior under Variable Field Conditions in View of Smart Agriculture Applications

To tackle the urgency of smarter crop management, the complex nature of agricultural ecosystems needs to be better understood, employing and combining different techniques and technologies. In this study, untargeted metabolomics and agro-meteorological survey were coupled to study the variation of Sorghum bicolor (L.) Moench metabolome during crop development, in response to environmental and anthropic factors. Twelve crop fields in the Emilia-Romagna region, Italy, were monitored and sampled at different stages, seedling (Ss), advanced vegetative (Sv), and ripening (Sr), and subjected to ¹H NMR-based metabolomics. The analytical method developed resulted to be successful to quickly analyze different sorghum organs. Dhurrin, a cyanogenic glucoside, resulted to be a biomarker of crop quality and development, and several insights into its turnover and functions were obtained. In particular, p-glucosyloxy-2-hydroxyphenylacetic acid was identified, for the first time, as the main metabolite accumulated in sorghum at Sr, after gradual dhurrin neutralization. During plant life, fertilization and biotic and abiotic stress reflected peculiar metabolomic profiles. Water supply and soil features (i.e., clay content) were correlated to metabolomic variations, affecting dhurrin (and related metabolites), amino acids, organic acids, and carbohydrate content. Increase in chlorogenic acid was registered in consequence of predator attacks. Moreover, grain from three fields presented traces of dhurrin and the lowest antioxidant potential, which resulted in poor grain quality. Metabolomics turned out to be a promising tool in view of smart agriculture for monitoring plant growth status and applying appropriate agricultural practices since the early stage of crop development.

Morphophysiological and biochemical attributes influence intra-genotypic preference of shoot fly [Atherigona soccata (Rondani)] among sorghum genotypes

Shoot fly [Atherigona soccata (Rondani)] is a destructive pest of sorghum at the seedling stage and causes huge losses to grain yield and green fodder. The host-plant resistance mechanism is the best approach to reduce the attack of insects in plants. The damage parameters, morphophysiological traits, and biochemical metabolites had been investigated in the leaves and stem of contrasting sorghum genotypes, viz., resistant (IS18551, ICSV705, ICSV700), moderately resistant (PSC-4), and susceptible (SWARNA and SL-44) at 15 and 21 days after emergence (DAE) against shoot fly infestation. The resistant genotypes recorded lowest shoot fly oviposition and incidence (0.3-0.7 eggs plant^-1 and 10-15%) than the susceptible genotypes (2.4-3.0 eggs plant^-1 and 70-80%), respectively. The susceptible genotype SWARNA recorded 50% and 80% higher deadheart formation than the resistant genotype IS18551 at 15 and 21 DAE, respectively. Resistant genotypes exhibited higher trichome density at adaxial and abaxial part of leaf (118-145 and 106-131) with pink colored leaf sheath (scale 1.50-3.25), glossy leaves (scale1.00-1.25), and lower leaf surface wetness (scale1.25-2.00) compared with susceptible genotype with 49.3-73.3 and 25.3-64.0, scale 2.50-4.00, scale 2.75-3.50, and scale 3.25-4.25 for the respective parameters. Another defense response of sorghum toward the insect attack was modulation of plant metabolism. The infested genotypes responded to insect attack by upregulation of total soluble sugar, total phenol, prussic acid, and chlorophyll content by 1.2-2.1-fold, 1.5-2.0-fold, 1.2-1.3-fold, and 1.2-3.9-fold with more induction in susceptible genotypes at 21 DAE. On the whole, the present study indicates that morphophysiological and biochemical attributes contribute toward the resistance mechanism in sorghum against shoot fly infestation.

Horizontal Gene Transfer: From Evolutionary Flexibility to Disease Progression

Flexibility in the exchange of genetic material takes place between different organisms of the same or different species. This phenomenon is known to play a key role in the genetic, physiological, and ecological performance of the host. Exchange of genetic materials can cause both beneficial and/or adverse biological consequences. Horizontal gene transfer (HGT) or lateral gene transfer (LGT) as a general mechanism leads to biodiversity and biological innovations in nature. HGT mediators are one of the genetic engineering tools used for selective introduction of desired changes in the genome for gene/cell therapy purposes. HGT, however, is crucial in development, emergence, and recurrence of various human-related diseases, such as cancer, genetic-, metabolic-, and neurodegenerative disorders and can negatively affect the therapeutic outcome by promoting resistant forms or disrupting the performance of genome editing toolkits. Because of the importance of HGT and its vital physio- and pathological roles, here the variety of HGT mechanisms are reviewed, ranging from extracellular vesicles (EVs) and nanotubes in prokaryotes to cell-free DNA and apoptotic bodies in eukaryotes. Next, we argue that HGT plays a role both in the development of useful features and in pathological states associated with emerging and recurrent forms of the disease. A better understanding of the different HGT mediators and their genome-altering effects/potentials may pave the way for the development of more effective therapeutic and diagnostic regimes.

The Interplay Between Water Limitation, Dhurrin, and Nitrate in the Low-Cyanogenic Sorghum Mutant adult cyanide deficient class 1

Sorghum bicolor (L.) Moench produces the nitrogen-containing natural product dhurrin that provides chemical defense against herbivores and pathogens via the release of toxic hydrogen cyanide gas. Drought can increase dhurrin in shoot tissues to concentrations toxic to livestock. As dhurrin is also a remobilizable store of reduced nitrogen and plays a role in stress mitigation, reductions in dhurrin may come at a cost to plant growth and stress tolerance. Here, we investigated the response to an extended period of water limitation in a unique EMS-mutant adult cyanide deficient class 1 (acdc1) that has a low dhurrin content in the leaves of mature plants. A mutant sibling line was included to assess the impact of unknown background mutations. Plants were grown under three watering regimes using a gravimetric platform, with growth parameters and dhurrin and nitrate concentrations assessed over four successive harvests. Tissue type was an important determinant of dhurrin and nitrate concentrations, with the response to water limitation differing between above and below ground tissues. Water limitation increased dhurrin concentration in the acdc1 shoots to the same extent as in wild-type plants and no growth advantage or disadvantage between the lines was observed. Lower dhurrin concentrations in the acdc1 leaf tissue when fully watered correlated with an increase in nitrate content in the shoot and roots of the mutant. In targeted breeding efforts to down-regulate dhurrin concentration, parallel effects on the level of stored nitrates should be considered in all vegetative tissues of this important forage crop to avoid potential toxic effects.

Role of cyanogenic glycosides in the seeds of wild lima bean, Phaseolus lunatus: defense, plant nutrition or both?

Cyanogenic glycosides present in the seeds of wild lima bean plants are associated with seedling defense but do not affect seed germination and seedling growth. Wild lima bean plants contain cyanogenic glycosides (CNGs) that are known to defend the plant against leaf herbivores. However, seed feeders appear to be unaffected despite the high levels of CNGs in the seeds. We investigated a possible role of CNGs in seeds as nitrogen storage compounds that influence plant growth, as well as seedling resistance to herbivores. Using seeds from four different wild lima bean natural populations that are known to vary in CNG levels, we tested two non-mutually exclusive hypotheses: (1) seeds with higher levels of CNGs produce seedlings that are more resistant against generalist herbivores and, (2) seeds with higher levels of CNGs germinate faster and produce plants that exhibit better growth. Levels of CNGs in the seeds were negatively correlated with germination rates and not correlated with seedling growth. However, levels of CNGs increased significantly soon after germination and seeds with the highest CNG levels produced seedlings with higher CNG levels in cotyledons. Moreover, the growth rate of the generalist herbivore Spodoptera littoralis was lower in cotyledons with high-CNG levels. We conclude that CNGs in lima bean seeds do not play a role in seed germination and seedling growth, but are associated with seedling defense. Our results provide insight into the potential dual function of plant secondary metabolites as defense compounds and storage molecules for growth and development.

Mechanisms in mutualisms: a chemically mediated thrips pollination strategy in common elder

This study provides first evidence of a thrips species pollinating Sambucus nigra and describes how interactions are driven by plant biochemical signalling and moderated by temporal changes in floral chemistry. The concept of flower-feeding thrips as pollinating insects in temperate regions is rarely considered as they are more frequently regarded to be destructive florivores feeding on pollen and surrounding plant tissue. Combining laboratory and field-based studies we examined interactions between Sambucus nigra (elderflower) and Thrips major within their native range to ascertain the role of thrips in the pollination of this species and to determine if floral chemicals mediated flower visits. If thrips provide a pollination service to S. nigra, then this will likely manifest in traits that attract the pollinating taxa at temporally critical points in floral development. T. major were highly abundant in inflorescences of S. nigra, entering flowers when stigmas were pollen-receptive and anthers were immature. When thrips were excluded from the inflorescences, fruit-set failed. Linalool was the major component of the inflorescence headspace with peak abundance coinciding with the highest number of adult thrips visiting flowers. Thrips were absent in buds and their numbers declined again in senescing flowers inversely correlating with the concentration of cyanogenic glycosides recorded in the floral tissue. Our data show that S. nigra floral chemistry mediates the behaviour of pollen-feeding thrips by attracting adults in high numbers to the flowers at pre-anthesis stage, while producing deterrent compounds prior to fruit development. Taking an integrative approach to studying thrips behaviour and floral biology we provide a new insight into the previously ambiguously defined pollination strategies of S. nigra and provide evidence suggesting that the relationship between T. major and S. nigra is mutualistic.

Sequestration and biosynthesis of cyanogenic glucosides in passion vine butterflies and consequences for the diversification of their host plants

The colorful heliconiine butterflies are distasteful to predators due to their content of defense compounds called cyanogenic glucosides (CNglcs), which they biosynthesize from aliphatic amino acids. Heliconiine larvae feed exclusively on Passiflora plants where ~30 kinds of CNglcs have been reported. Among them, some CNglcs derived from cyclopentenyl glycine can be sequestered by some Heliconius species. In order to understand the evolution of biosynthesis and sequestration of CNglcs in these butterflies and its consequences for their arms race with Passiflora plants, we analyzed the CNglc distribution in selected heliconiine and Passiflora species. Sequestration of cyclopentenyl CNglcs is not an exclusive trait of Heliconius, since these compounds were present in other heliconiines such as Philaethria, Dryas and Agraulis, and in more distantly related genera Cethosia and Euptoieta. Thus, it is likely that the ability to sequester cyclopentenyl CNglcs arose in an ancestor of the Heliconiinae subfamily. Biosynthesis of aliphatic CNglcs is widespread in these butterflies, although some species from the sara-sapho group seem to have lost this ability. The CNglc distribution within Passiflora suggests that they might have diversified their cyanogenic profile to escape heliconiine herbivory. This systematic analysis improves our understanding on the evolution of cyanogenesis in the heliconiine-Passiflora system.

Effects of toxic β-glucosides on carbohydrate metabolism in cotton bollworm, Helicoverpa armigera (Hübner)

The purpose of this study was to evaluate the effects of three toxic β-glucosides, phlorizin, santonin, and amygdalin, on carbohydrate metabolism in the cotton bollworm, Helicoverpa armigera (Hübner), when diets mixed with β-glucosides were fed to third-instar larvae. The growth of the larvae was significantly inhibited by exposure to santonin after 96 hr but not obviously affected by phlorizin and amygdalin. The midgut trehalase activities were only 51.7%, 32%, and 42.5% of that of the control after treatment with phlorizin, santonin and amygdalin at 2 mg/ml, respectively. In the hemolymph and fat body, the amount of trehalose decreased in all cases. However, the effects of santonin on the alteration of the glycogen and glucose levels as well as the activities of glycogen phosphorylase, were different than those of the other two β-glucosides. It appears that the three β-glucosides have different influences on the carbohydrate metabolism of cotton bollworm.

Cyanide and lactate levels in patients during chronic oral amygdalin intake followed by intravenous amygdalin administration

The natural compound amygdalin has gained high popularity among tumor patients as a complementary or alternative treatment option. However, due to metabolization of amygdalin to cyanide (HCN) following oral consumption, there could be a high risk of lactic acidosis caused by cyanide intoxication. The present retrospective study was undertaken to evaluate cyanide blood and lactate plasma levels of tumor patients (n = 55) before and after intravenous (i.v.) amygdalin infusion. All patients had also continuously ingested amygdalin tablets (3 x 500 mg/day), excepting on the days of i.v. administration. Each patient received one to five intravenous amygdalin treatments. The time period between each i.v. application ranged between 4-6 days. The initial i.v. dose was 6 mg (n = 28), 9 mg (n = 1), 15 mg (n = 1) or 18 mg (n = 25). The mean cyanide blood level before i.v. amygdalin administration was 34.74 μg/L, which increased significantly to a mean value of 66.20 μg/L after i. v. amygdalin application. In contrast, lactate decreased significantly from 1266 μmol/L pre-infusion to 868 μmol/L post-infusion. Increasing i.v. amygdalin by 1 mg was also associated with a significant increase in the cyanide level, while the lactate blood level significantly decreased. This is the first study evaluating cyanide levels under conditions employed by amygdalin administrators, i.e. after chronic oral amygdalin intake and then again after a closely subsequent intravenous amygdalin administration. Since lactate decreased, whilst cyanide increased, it is concluded that elevation of cyanide does not induce metabolic acidosis in terms of an increased lactate level.

Comparative transcriptome analysis reveals significant differences in the regulation of gene expression between hydrogen cyanide- and ethylene-treated Arabidopsis thaliana

BACKGROUND

Hydrogen cyanide (HCN) is a small gaseous molecule that is predominantly produced as an equimolar co-product of ethylene (ET) biosynthesis in plants. The function of ET is of great concern and is well studied; however, the function of HCN is largely unknown. Similar to ET, HCN is a simple and diffusible molecule that has been shown to play a regulatory role in the control of some metabolic processes in plants. Nevertheless, it is still controversial whether HCN should be regarded as a signalling molecule, and the cross-talk between HCN and ET in gene expression regulation remains unclear. In this study, RNA sequencing (RNA-seq) was performed to compare the differentially expressed genes (DEGs) between HCN and ET in Arabidopsis. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were subsequently performed to investigate the function and pathway enrichment of DEGs. Parts of key genes were confirmed by quantitative real-time PCR.

RESULTS

The results showed that at least 1305 genes and 918 genes were significantly induced by HCN and ET, respectively. Interestingly, a total of 474 genes (|log₂ FC| ≥1) were co-regulated by HCN and ET. GO and KEGG analyses indicated that the co-regulated genes by HCN and ET were enriched in plant responses to stress and plant hormone signal transduction pathways, indicating that HCN may cooperate with ET and participate in plant growth and development and stress responses. However, a total of 831 genes were significantly induced by HCN but not by ET, indicating that in addition to ET, HCN is in essence a key signalling molecule in plants. Importantly, our data showed that the possible regulatory role of a relatively low concentration of HCN does not depend on ET feedback induction, although there are some common downstream components were observed.

CONCLUSION

Our findings provide a valuable resource for further exploration and understanding of the molecular regulatory mechanisms of HCN in plants and provide novel insight into HCN cross-talk with ET and other hormones in the regulation of plant growth and plant responses to environmental stresses.

The linker length of glucose-fipronil conjugates has a major effect on the rate of bioactivation by β-glucosidase

BACKGROUND

Endogenous plant β-glucosidases can be utilized to hydrolyze pro-pesticides and release the bioactive pesticide. Two related glucose-fipronil conjugates with different linkers structure, N-{3-cyano-1-[2,6-dichloro-4-(trifluoromethyl) phenyl]-4-[(trifluoromethyl) sulfinyl]-1H-pyrazol-5-yl}-1-(2-triazolethyl-β-d-glucopyranoside)-1H-1,2,3-triazole-4-methanamine (GOTF) and N-{3-cyano-1-[2,6-dichloro-4-(trifluoromethyl) phenyl]-4-[(trifluoromethyl)-sulfinyl]-1H-pyrazol-5-yl}-2-aminoethyl-β-d-glucopyranoside (GOF), were deglucolysated by β-glucosidase both in vitro and in vivo at different rates. Here, the basis for these differences was investigated by revealing the kinetics of the reaction and by modeling molecular docking between enzyme and substrate.

RESULTS

Results from kinetic study showed that the reaction rate was the main reason for the poorer rate of GOF hydrolysis with respect to GOTF. Modeling of substrate docking indicated that the spacer arm of glucose-fipronil conjugates affects the strength of non-covalent bonds within the active site and the position of fipronil within the pocket. Four glucose-fipronil conjugates and four corresponding aglycones were synthesized, and the hydrolysis data confirmed that the increased tether length between the bulky aglycone and glycone would lead to faster hydrolysis rate. The bioassay results indicated that most glucose-fipronil conjugates displayed moderate to excellent insecticidal activities in vivo against Plutella xylostella larvae.

CONCLUSION

This study provides a potential strategy to optimize the substrate structure to enhance hydrolytic specificity in order to design appropriate phloem mobile pro-pesticides. © 2018 Society of Chemical Industry.

Untargeted Metabolomics Approach Reveals Differences in Host Plant Chemistry Before and After Infestation With Different Pea Aphid Host Races

The pea aphid (Acyrthosiphon pisum), a phloem-sucking insect, has undergone a rapid radiation together with the domestication and anthropogenic range expansion of several of its legume host plants. This insect species is a complex of at least 15 genetically different host races that can all develop on the universal host plant Vicia faba. However, each host race is specialized on a particular plant species, such as Medicago sativa, Trifolium pratense, or Pisum sativum, which makes it an attractive model insect to study ecological speciation. Previous work revealed that pea aphid host plants produce a specific phytohormone profile depending on the host plant - host race combination. Native aphid races induce lower defense hormone levels in their host plant than non-native pea aphid races. Whether these changes in hormone levels also lead to changes in other metabolites is still unknown. We used a mass spectrometry-based untargeted metabolomic approach to identify plant chemical compounds that vary among different host plant-host race combinations and might therefore, be involved in pea aphid host race specialization. We found significant differences among the metabolic fingerprints of the four legume species studied prior to aphid infestation, which correlated with aphid performance. After infestation, the metabolic profiles of M. sativa and T. pratense plants infested with their respective native aphid host race were consistently different from profiles after infestation with non-native host races and from uninfested control plants. The metabolic profiles of P. sativum plants infested with their native aphid host race were also different from plants infested with non-native host races, but not different from uninfested control plants. The compounds responsible for these differences were putatively identified as flavonoids, saponins, non-proteinogenic amino acids and peptides among others. As members of these compound classes are known for their activity against insects and aphids in particular, they may be responsible for the differential performance of host races on native vs. non-native host plants. We conclude that the untargeted metabolomic approach is suitable to identify candidate compounds involved in the specificity of pea aphid - host plant interactions.

Lineage-specific duplication and adaptive evolution of bitter taste receptor genes in bats

By generating raw genetic material and diverse biological functions, gene duplication represents a major evolutionary mechanism that is of fundamental importance in ecological adaptation. The lineage-specific duplication events of bitter taste receptor genes (Tas2rs) have been identified in a number of vertebrates, but functional evolution of new Tas2r copies after duplication remains largely unknown. Here, we present the largest data set of bat Tas2rs to date, identified from existing genome sequences of 15 bat species and newly sequenced from 17 bat species, and demonstrate lineage-specific duplications of Tas2r16, Tas2r18 and Tas2r41 that only occurred in Myotis bats. Myotis bats are highly speciose and represent the only mammalian genus that is naturally distributed on every continent except Antarctica. The occupation of such diverse habitats might have driven the Tas2r gene expansion. New copies of Tas2rs in Myotis bats have shown molecular adaptation and functional divergence. For example, three copies of Tas2r16 in Myotis davidii showed differential sensitivities to arbutin and salicin that may occur in their insect prey, as suggested by cell-based functional assays. We hypothesize that functional differences among Tas2r copies in Myotis bats would increase their survival rate through preventing the ingestion of an elevated number of bitter-tasting dietary toxins from their insect prey, which may have facilitated their adaptation to diverse habitats. Our study demonstrates functional changes of new Tas2r copies after lineage-specific duplications in Myotis bats and highlights the potential role of taste perception in exploiting new environments.