Phytochemical analysis and antihyperglycemic activity of Castilleja arvensis.

Castilleja genus comprises approximately 211 species, some of them exhibiting potential in treating various diseases. Remarkably, despite its abundance, there is a significant lack of scientific studies that explore the chemical composition and/or therapeutic activity of this genus. In this work, the chemical composition of Castilleja arvensis was determined, and its antihyperglycemic activity was evaluated in vivo, in vitro, and ex vivo. Hydroalcoholic extract of C. arvensis (HECa) was obtained from the maceration of aerial parts. HECa was fractionated by liquid-liquid extractions to obtain the CH2Cl2 fraction (DF), EtOAc fraction (EF), n-BuOH fraction (BF) and aqueous residue (AR). The antihyperglycemic activity was determined in vivo through oral glucose and sucrose tolerance tests in normoglycemic CD-1 mice. Ex vivo assays were performed to determine intestinal glucose absorption, muscular glucose uptake and hepatic glucose production. α-glucosidase inhibitory activity was evaluated in vitro. Phytochemical screening was carried out through conventional chromatography techniques. Structure elucidation of the isolated compounds was performed by GC-MS and NMR experiments. HECa, its fractions and AR showed significant antihyperglycemic activity in vivo. According to the in vitro and ex vivo assays, this effect can be attributed to different mechanisms of action, including a delay in intestinal glucose absorption, an improvement in insulin sensitivity, and the regulation of hepatic glucose production. These effects may be due to different metabolites identified in fractions from the HECa, including genkwanin, acacetin, verbascoside and ipolamiide. Thus, current research shows that C. arvensis is an important source of bioactive compounds for the management of glycemia.

Mixed elicitation with salicylic acid and hydrogen peroxide modulates the phenolic and iridoid pathways in Castilleja tenuiflora plants.

MAIN CONCLUSION: SA and H2O2, in single and mixed elicitation stimulate specialized metabolism and activate oxidative stress in C. tenuiflora plants. Single elicitation with salicylic acid (SA at 75 µM) and, hydrogen peroxide (at 150 µM), and mixed elicitation (75 µM SA + 150 µM H2O2) were evaluated on specialized metabolism in Castilleja tenuiflora Benth. plants. Total phenolic content (TPC), phenylalanine ammonia-lyase (PAL) activity, antioxidant enzymes and specialized metabolite profiles, as well as the expression levels of eight genes involved in phenolic (Cte-TyrDC, Cte-GOT2, Cte-ADD, Cte-AO3, Cte-PAL1, Cte-CHS1) and terpene pathways (Cte-DXS1 and Cte-G10H) and their correlation with major metabolite (verbascoside and aucubin) concentrations were investigated. TPC content (three-fold) and PAL activity (11.5-fold) increased with mixed elicitation, as well as catalase and peroxidase activity (11.3-fold and 10.8-fold, respectively), compared to single elicitation. Phenylethanoid accumulation was greatest under mixed elicitation, followed by SA and H2O2. Lignan accumulation was differential, depending on the plant part and the elicitor. Flavonoids only appeared after mixed elicitation. The high concentration of verbascoside under mixed elicitation was related to a high gene expression. Single elicitation induced iridoid accumulation in specific parts (H2O2 in aerial parts and SA in roots), whereas under mixed elicitation, it accumulated in both parts. A high concentration of aucubin in the aerial part was related to a high expression level of genes of the terpene pathway Cte-DXS1 and Cte-G10H, and in the root with Cte-G10H, while Cte-DXS1 was downregulated in this tissue in all treatments. Mixed elicitation with SA and H2O2 represents an interesting tool to increase the production of specialized metabolites in plants.

Pectin modifications promote haustoria development in the parasitic plant Phtheirospermum japonicum.

Parasitic plants are globally prevalent pathogens with important ecological functions but also potentially devastating agricultural consequences. Common to all parasites is the formation of the haustorium which requires parasite organ development and tissue invasion into the host. Both processes involve cell wall modifications. Here, we investigated a role for pectins during haustorium development in the facultative parasitic plant Phtheirospermum japonicum. Using transcriptomics data from infected Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa), we identified genes for multiple P. japonicum pectin methylesterases (PMEs) and their inhibitors (PMEIs) whose expression was upregulated by haustoria formation. Changes in PME and PMEI expression were associated with tissue-specific modifications in pectin methylesterification. While de-methylesterified pectins were present in outer haustorial cells, highly methylesterified pectins were present in inner vascular tissues, including the xylem bridge that connects parasite to host. Specifically blocking xylem bridge formation in the haustoria inhibited several PME and PMEI genes from activating. Similarly, inhibiting PME activity using chemicals or by overexpressing PMEI genes delayed haustoria development. Our results suggest a dynamic and tissue-specific regulation of pectin contributes to haustoria initiation and to the establishment of xylem connections between parasite and host.

Cytokinins Induce Prehaustoria Coordinately with Quinone Signals in the Parasitic Plant Striga hermonthica.

Orobanchaceae parasitic plants are major threats to global food security, causing severe agricultural damage worldwide. Parasitic plants derive water and nutrients from their host plants through multicellular organs called haustoria. The formation of a prehaustorium, a primitive haustorial structure, is provoked by host-derived haustorium-inducing factors (HIFs). Quinones, including 2,6-dimethoxy-p-benzoquinone (DMBQ), are of the most potent HIFs for various species in Orobanchaceae, but except non-photosynthetic holoparasites, Phelipanche and Orobanche spp. Instead, cytokinin (CK) phytohormones were reported to induce prehaustoria in Phelipanche ramosa. However, little is known about whether CKs act as HIFs in the other parasitic species to date. Moreover, the signaling pathways for quinones and CKs in prehaustorium induction are not well understood. This study shows that CKs act as HIFs in the obligate parasite Striga hermonthica but not in the facultative parasite Phtheirospermum japonicum. Using chemical inhibitors and marker gene expression analysis, we demonstrate that CKs activate prehaustorium formation through a CK-specific signaling pathway that overlaps with the quinone HIF pathway at downstream in S. hermonthica. Moreover, host root exudates activated S. hermonthica CK biosynthesis and signaling genes, and DMBQ and CK inhibitors perturbed the prehaustorium-inducing activity of exudates, indicating that host root exudates include CKs. Our study reveals the importance of CKs for prehaustorium formation in obligate parasitic plants.

Strigolactones are chemoattractants for host tropism in Orobanchaceae parasitic plants.

Parasitic plants are worldwide threats that damage major agricultural crops. To initiate infection, parasitic plants have developed the ability to locate hosts and grow towards them. This ability, called host tropism, is critical for parasite survival, but its underlying mechanism remains mostly unresolved. To characterise host tropism, we used the model facultative root parasite Phtheirospermum japonicum, a member of the Orobanchaceae. Here, we show that strigolactones (SLs) function as host-derived chemoattractants. Chemotropism to SLs is also found in Striga hermonthica, a parasitic member of the Orobanchaceae, but not in non-parasites. Intriguingly, chemotropism to SLs in P. japonicum is attenuated in ammonium ion-rich conditions, where SLs are perceived, but the resulting asymmetrical accumulation of the auxin transporter PIN2 is diminished. P. japonicum encodes putative receptors that sense exogenous SLs, whereas expression of a dominant-negative form reduces its chemotropic ability. We propose a function for SLs as navigators for parasite roots.

A Phelipanche ramosa KAI2 protein perceives strigolactones and isothiocyanates enzymatically.

Phelipanche ramosa is an obligate root-parasitic weed that threatens major crops in central Europe. In order to germinate, it must perceive various structurally divergent host-exuded signals, including isothiocyanates (ITCs) and strigolactones (SLs). However, the receptors involved are still uncharacterized. Here, we identify five putative SL receptors in P. ramosa and show that PrKAI2d3 is involved in the stimulation of seed germination. We demonstrate the high plasticity of PrKAI2d3, which allows it to interact with different chemicals, including ITCs. The SL perception mechanism of PrKAI2d3 is similar to that of endogenous SLs in non-parasitic plants. We provide evidence that PrKAI2d3 enzymatic activity confers hypersensitivity to SLs. Additionally, we demonstrate that methylbutenolide-OH binds PrKAI2d3 and stimulates P. ramosa germination with bioactivity comparable to that of ITCs. This study demonstrates that P. ramosa has extended its signal perception system during evolution, a fact that should be considered for the development of specific and efficient biocontrol methods.

How do holoparasitic plants exploit vitamin K1?

Phylloquinone (vitamin K1) is a thylakoid-embedded electron carrier essential for photosynthesis. Paradoxically, we found that phylloquinone biosynthesis is retained in the nonphotosynthetic holoparasite Phelipanche aegyptiaca (Egyptian broomrape). The phylloquinone pathway genes are preferentially expressed during development of the invasive organ, the haustorium, and exhibit strong coexpression with redox-active proteins known to be involved in parasitism. Unlike in photoautotrophic taxa, the late pathway genes of the holoparasite lack the chloroplast-targeting sequence and their proteins are targeted to the plasma membrane instead. Plasma membrane phylloquinone may enable Phelipanche to sense changes in the redox environment during host interactions. The N-truncated isoforms are conserved in several other Orobanchaceae root holoparasites, and interestingly, in a number of closely related photoautotrophic species as well. This suggests an ancient origin of distinct phylloquinone pathways predating the evolution of parasitic plants in the Orobanchaceae. These findings represent exciting opportunities to probe plasma membrane phylloquinone function and diversification in parasitic and nonparasitic plant responses to external redox chemistry in the rhizosphere.

Impact of the facultative parasitic weed Rhamphicarpa fistulosa (Hochst.) Benth. on photosynthesis of its host Oryza sativa L.

Rhamphicarpa fistulosa is a facultative root parasitic annual forb, of the family Orobanchaceae that is native to sub-Saharan Africa. Parasitism results in yield reductions by the host plants but it is not known how exactly R. fistulosa affects its host or how the host responds physiologically. In three pot experiments, we investigated whether and when the parasite affects photosynthesis of rice, whether the level of impact was parasite density dependent and explored mechanisms underlying the response of rice photosynthesis to parasitism. Photosynthesis and related parameters were measured at a range of light use intensities. Host photosynthesis was negatively affected while light use efficiency was negatively affected only later on in the growth process. Except for dark respiration rates, which were never affected by parasite infection, suppression of host photosynthesis at light saturation, the initial light-use efficiency, chlorophyll content, specific leaf area and shoot weight were parasite density dependent with a stronger effect for higher parasite densities. Only at 56 days after sowing, the slope of the linear relationship between light adapted quantum efficiency of PSII electron transport (ΦPSII) and the quantum yield of CO2 assimilation (ΦCO2) of infected plants was less than those of un-infected plants. There was a considerable time lag between the parasite's acquisition of benefits from the association, in terms of growth (previously observed around 42 DAS), and the reduction of host photosynthesis (around 56 DAS). Expression of relative reductions in host growth rates started at the same time as the relative suppression of host photosynthesis. This indicated that R. fistulosa affects host growth by first extracting assimilates and making considerable gains in growth, before impacting host photosynthesis and growth.

Subtilase activity in intrusive cells mediates haustorium maturation in parasitic plants.

Parasitic plants that infect crops are devastating to agriculture throughout the world. These parasites develop a unique inducible organ called the haustorium that connects the vascular systems of the parasite and host to establish a flow of water and nutrients. Upon contact with the host, the haustorial epidermal cells at the interface with the host differentiate into specific cells called intrusive cells that grow endophytically toward the host vasculature. Following this, some of the intrusive cells re-differentiate to form a xylem bridge (XB) that connects the vasculatures of the parasite and host. Despite the prominent role of intrusive cells in host infection, the molecular mechanisms mediating parasitism in the intrusive cells remain poorly understood. In this study, we investigated differential gene expression in the intrusive cells of the facultative parasite Phtheirospermum japonicum in the family Orobanchaceae by RNA-sequencing of laser-microdissected haustoria. We then used promoter analyses to identify genes that are specifically induced in intrusive cells, and promoter fusions with genes encoding fluorescent proteins to develop intrusive cell-specific markers. Four of the identified intrusive cell-specific genes encode subtilisin-like serine proteases (SBTs), whose biological functions in parasitic plants are unknown. Expression of SBT inhibitors in intrusive cells inhibited both intrusive cell and XB development and reduced auxin response levels adjacent to the area of XB development. Therefore, we propose that subtilase activity plays an important role in haustorium development in P. japonicum.

Plasma membrane phylloquinone biosynthesis in nonphotosynthetic parasitic plants.

Nonphotosynthetic holoparasites exploit flexible targeting of phylloquinone biosynthesis to facilitate plasma membrane redox signaling. Phylloquinone is a lipophilic naphthoquinone found predominantly in chloroplasts and best known for its function in photosystem I electron transport and disulfide bridge formation of photosystem II subunits. Phylloquinone has also been detected in plasma membrane (PM) preparations of heterotrophic tissues with potential transmembrane redox function, but the molecular basis for this noncanonical pathway is unknown. Here, we provide evidence of PM phylloquinone biosynthesis in a nonphotosynthetic holoparasite Phelipanche aegyptiaca. A nonphotosynthetic and nonplastidial role for phylloquinone is supported by transcription of phylloquinone biosynthetic genes during seed germination and haustorium development, by PM-localization of alternative terminal enzymes, and by detection of phylloquinone in germinated seeds. Comparative gene network analysis with photosynthetically competent parasites revealed a bias of P. aegyptiaca phylloquinone genes toward coexpression with oxidoreductases involved in PM electron transport. Genes encoding the PM phylloquinone pathway are also present in several photoautotrophic taxa of Asterids, suggesting an ancient origin of multifunctionality. Our findings suggest that nonphotosynthetic holoparasites exploit alternative targeting of phylloquinone for transmembrane redox signaling associated with parasitism.

Preference, performance, and chemical defense in an endangered butterfly using novel and ancestral host plants.

Adoption of novel host plants by herbivorous insects can require new adaptations and may entail loss of adaptation to ancestral hosts. We examined relationships between an endangered subspecies of the butterfly Euphydryas editha (Taylor's checkerspot) and three host plant species. Two of the hosts (Castilleja hispida, Castilleja levisecta) were used ancestrally while the other, Plantago lanceolata, is exotic and was adopted more recently. We measured oviposition preference, neonate preference, larval growth, and secondary chemical uptake on all three hosts. Adult females readily laid eggs on all hosts but favored Plantago and tended to avoid C. levisecta. Oviposition preference changed over time. Neonates had no preference among host species, but consistently chose bracts over leaves within both Castilleja species. Larvae developed successfully on all species and grew to similar size on all of them unless they ate only Castilleja leaves (rather than bracts) which limited their growth. Diet strongly influenced secondary chemical uptake by larvae. Larvae that ate Plantago or C. hispida leaves contained the highest concentrations of iridoid glycosides, and iridoid glycoside composition varied with host species and tissue type. Despite having largely switched to a novel exotic host and generally performing better on it, this population has retained breadth in preference and ability to use other hosts.

Strigolactones and Auxin Cooperate to Regulate Maize Root Development and Response to Nitrate.

In maize, nitrate regulates root development thanks to the coordinated action of many players. In this study, the involvement of strigolactones (SLs) and auxin as putative components of the nitrate regulation of lateral root (LR) was investigated. To this aim, the endogenous SL content of maize root in response to nitrate was assessed by liquid chromatography with tandem mass Spectrometry (LC-MS/MS) and measurements of LR density in the presence of analogues or inhibitors of auxin and SLs were performed. Furthermore, an untargeted RNA-sequencing (RNA-seq)-based approach was used to better characterize the participation of auxin and SLs to the transcriptional signature of maize root response to nitrate. Our results suggested that N deprivation induces zealactone and carlactonoic acid biosynthesis in root, to a higher extent if compared to P-deprived roots. Moreover, data on LR density led to hypothesize that the induction of LR development early occurring upon nitrate supply involves the inhibition of SL biosynthesis, but that the downstream target of SL shutdown, besides auxin, also includes additional unknown players. Furthermore, RNA-seq results provided a set of putative markers for the auxin- or SL-dependent action of nitrate, meanwhile also allowing to identify novel components of the molecular regulation of maize root response to nitrate. Globally, the existence of at least four different pathways was hypothesized: one dependent on auxin, a second one mediated by SLs, a third deriving from the SL-auxin interplay, and a last one attributable to nitrate itself through further downstream signals. Further work will be necessary to better assess the reliability of the model proposed.

Overexpression of RgPAL family genes involved in phenolic biosynthesis promotes the replanting disease development in Rehmannia glutinosa.

Rehmannia glutinosa production is affected by the replanting disease, which involves autotoxic harm mediated by specific endogenous allelochemicals in root exudates. Many phenolics that act as allelochemical agents are mostly phenylpropanoid products of secondary metabolism in plants. Phenylalanine ammonia-lyase (PAL) is the first enzyme that catalyses the deamination of l-phenylalanine for entrance into the phenylpropanoid pathway. PAL family genes have been isolated and functionally characterized in many plant species. However, PAL family genes involved in phenolic biosynthesis remain largely uncharacterized in R. glutinosa. Here, we identified and characterized four PAL family genes (RgPAL2 to RgPAL5) in the species whose sequences exhibited highly conserved domains of PALs according to in silico analysis, implying their potential function in phenolic biosynthesis. Overexpression of RgPALs in R. glutinosa enhanced phenolic production, verifying that RgPAL family genes participate in phenolic biosynthesis pathways. Moreover, we found that the release of several allelopathic phenolics from the roots of RgPAL-overexpressing transgenic R. glutinosa increased, implying that the RgPALs positively promote their release. Importantly, under continuous monoculture stress, we found that the RgPAL transgenic plants exhibited more significant autotoxic harm than did non-transgenic (WT) plants by activating the phenolics/phenylpropanoid pathway, indicating that RgPAL family genes function as positive regulators of the replanting disease development in R. glutinosa. This study revealed that RgPAL family genes are involved in the biosynthesis and release of several phenolics and positively control the replanting disease development in R. glutinosa, laying a foundation for further clarification of the molecular mechanisms underlying the disease formation.

An auxin transport network underlies xylem bridge formation between the hemi-parasitic plant Phtheirospermum japonicum and host Arabidopsis.

Parasitic plants form vascular connections with host plants for efficient material transport. The haustorium is the responsible organ for host invasion and subsequent vascular connection. After invasion of host tissues, vascular meristem-like cells emerge in the central region of the haustorium, differentiate into tracheary elements and establish a connection, known as a xylem bridge, between parasite and host xylem systems. Despite the importance of this parasitic connection, the regulatory mechanisms of xylem bridge formation are unknown. Here, we show the role of auxin and auxin transporters during the process of xylem bridge formation using an Orobanchaceae hemiparasitic plant, Phtheirospermum japonicum The auxin response marker DR5 has a similar expression pattern to tracheary element differentiation genes in haustoria. Auxin transport inhibitors alter tracheary element differentiation in haustoria, but biosynthesis inhibitors do not, demonstrating the importance of auxin transport during xylem bridge formation. The expression patterns and subcellular localization of PIN family auxin efflux carriers and AUX1/LAX influx carriers correlate with DR5 expression patterns. The cooperative action of auxin transporters is therefore responsible for controlling xylem vessel connections between parasite and host.

Analysis of Centranthera grandiflora Benth Transcriptome Explores Genes of Catalpol, Acteoside and Azafrin Biosynthesis.

Cardiovascular diseases (CVDs) are a major cause of health loss in the world. Prevention and treatment of this disease by traditional Chinese medicine is a promising method. Centranthera grandiflora Benth is a high-value medicinal herb in the prevention and treatment of CVDs; its main medicinal components include iridoid glycosides, phenylethanoid glycosides, and azafrin in roots. However, biosynthetic pathways of these components and their regulatory mechanisms are unknown. Furthermore, there are no genomic resources of this herb. In this article, we provide sequence and transcript abundance data for the root, stem, and leaf transcriptome of C. grandiflora Benth obtained by the Illumina Hiseq2000. More than 438 million clean reads were obtained from root, stem, and leaf libraries, which produced 153,198 unigenes. Based on databases annotation, a total of 557, 213, and 161 unigenes were annotated to catalpol, acteoside, and azafrin biosynthetic pathways, respectively. Differentially expressed gene analysis identified 14,875 unigenes differentially enriched between leaf and root with 8,054 upregulated genes and 6,821 downregulated genes. Candidate MYB transcription factors involved in catalpol, acteoside, and azafrin biosynthesis were also predicated. This work is the first transcriptome analysis in C. grandiflora Benth which will aid the deciphering of biosynthesis pathways and regulatory mechanisms of active components.

Genome-wide identification of MST, SUT and SWEET family sugar transporters in root parasitic angiosperms and analysis of their expression during host parasitism.

BACKGROUND: Root parasitic weeds are a major constraint to crop production worldwide causing significant yearly losses in yield and economic value. These parasites cause their destruction by attaching to their hosts with a unique organ, the haustorium, that allows them to obtain the nutrients (sugars, amino acids, etc.) needed to complete their lifecycle. Parasitic weeds differ in their nutritional requirements and degree of host dependency and the differential expression of sugar transporters is likely to be a critical component in the parasite's post-attachment survival. RESULTS: We identified gene families encoding monosaccharide transporters (MSTs), sucrose transporters (SUTs), and SWEETs (Sugars Will Eventually be Exported Transporters) in three root-parasitic weeds differing in host dependency: Triphysaria versicolor (facultative hemiparasite), Phelipanche aegyptiaca (holoparasite), and Striga hermonthica (obligate hemiparasite). The phylogenetic relationship and differential expression profiles of these genes throughout parasite development were examined to uncover differences existing among parasites with different levels of host dependence. Differences in estimated gene numbers are found among the three parasites, and orthologs within the different sugar transporter gene families are found to be either conserved among the parasites in their expression profiles throughout development, or to display parasite-specific differences in developmentally-timed expression. For example, MST genes in the pGLT clade express most highly before host connection in Striga and Triphysaria but not Phelipanche, whereas genes in the MST ERD6-like clade are highly expressed in the post-connection growth stages of Phelipanche but highest in the germination and reproduction stages in Striga. Whether such differences reflect changes resulting from differential host dependence levels is not known. CONCLUSIONS: While it is tempting to speculate that differences in estimated gene numbers and expression profiles among members of MST, SUT and SWEET gene families in Phelipanche, Striga and Triphysaria reflect the parasites' levels of host dependence, additional evidence that altered transporter gene expression is causative versus consequential is needed. Our findings identify potential targets for directed manipulation that will allow for a better understanding of the nutrient transport process and perhaps a means for controlling the devastating effects of these parasites on crop productivity.

ABA signaling components in Phelipanche aegyptiaca.

Obligate root holoparasite Phelipanche aegyptiaca is an agricultural pest, which infests its hosts and feeds on the sap, subsequently damaging crop yield and quality. Its notoriously viable seed bank may serve as an ideal pest control target. The phytohormone abscisic acid (ABA) was shown to regulate P. aegyptiaca seed dormancy following strigolactones germination stimulus. Transcription analysis of signaling components revealed five ABA receptors and two co-receptors (PP2C). Transcription of lower ABA-affinity subfamily III receptors was absent in all tested stages of P. aegyptiaca development and parasitism stages. P. aegyptiaca ABA receptors interacted with the PP2Cs, and inhibited their activity in an ABA-dependent manner. Moreover, sequence analysis revealed multiple alleles in two P. aegyptiaca ABA receptors, with many non-synonymous mutations. Functional analysis of selected receptor alleles identified a variant with substantially decreased inhibitory effect of PP2Cs activity in-vitro. These results provide evidence that P. aegyptiaca is capable of biochemically perceiving ABA. In light of the possible involvement of ABA in parasitic activities, the discovery of active ABA receptors and PP2Cs could provide a new biochemical target for the agricultural management of P. aegyptiaca. Furthermore, the potential genetic loss of subfamily III receptors in this species, could position P. aegyptiaca as a valuable model in the ABA perception research field.

Host Plant Suitability in a Specialist Herbivore, Euphydryas anicia (Nymphalidae): Preference, Performance and Sequestration.

The checkerspot butterfly, Euphydryas anicia (Nymphalidae), specializes on plants containing iridoid glycosides and has the ability to sequester these compounds from its host plants. This study investigated larval preference, performance, and sequestration of iridoid glycosides in a population of E. anicia at Crescent Meadows, Colorado, USA. Although previous studies showed that other populations in Colorado use the host plant, Castilleja integra (Orobanchaceae), we found no evidence for E. anicia ovipositing or feeding on C. integra at Crescent Meadows. Though C. integra and another host plant, Penstemon glaber (Plantaginaceae), occur at Crescent Meadows, the primary host plant used was P. glaber. To determine why C. integra was not being used at the Crescent Meadows site, we first examined the host plant preference of naïve larvae between P. glaber and C. integra. Then we assessed the growth and survivorship of larvae reared on each plant species. Finally, we quantified the iridoid glycoside concentrations of the two plant species and diapausing caterpillars reared on each host plant. Our results showed that E. anicia larvae prefer P. glaber. Also, larvae survive and grow better when reared on P. glaber than on C. integra. Castilleja integra was found to contain two primary iridoid glycosides, macfadienoside and catalpol, and larvae reared on this plant sequestered both compounds; whereas P. glaber contained only catalpol and larvae reared on this species sequestered catalpol. Thus, although larvae are able to use C. integra in the laboratory, the drivers behind the lack of use at the Crescent Meadows site remain unclear.

Aeginetia indica Decoction Inhibits Hepatitis C Virus Life Cycle.

Chronic hepatitis C virus (HCV) infection is still a global epidemic despite the introduction of several highly effective direct-acting antivirals that are tagged with sky-high prices. The present study aimed to identify an herbal decoction that ameliorates HCV infection. Among six herbal decoctions tested, the Aeginetia indica decoction had the most profound effect on the HCV reporter activity in infected Huh7.5.1 liver cells in a dose- and time-dependent manner. The Aeginetia indica decoction exerted multiple inhibitory effects on the HCV life cycle. Pretreatment of the cells with the Aeginetia indica decoction prior to HCV infection reduced the HCV RNA and non-structural protein 3 (NS3) protein levels in the infected cells. The Aeginetia indica decoction reduced HCV internal ribosome entry site-mediated protein translation activity. It also reduced the HCV RNA level in the infected cells in association with reduced NS5A phosphorylation at serine 235, a predominant phosphorylation event indispensable to HCV replication. Thus, the Aeginetia indica decoction inhibits HCV infection, translation, and replication. Mechanistically, the Aeginetia indica decoction probably reduced HCV replication via reducing NS5A phosphorylation at serine 235.

Seed germination in parasitic plants: what insights can we expect from strigolactone research?

Obligate root-parasitic plants belonging to the Orobanchaceae family are deadly pests for major crops all over the world. Because these heterotrophic plants severely damage their hosts even before emerging from the soil, there is an unequivocal need to design early and efficient methods for their control. The germination process of these species has probably undergone numerous selective pressure events in the course of evolution, in that the perception of host-derived molecules is a necessary condition for seeds to germinate. Although most of these molecules belong to the strigolactones, structurally different molecules have been identified. Since strigolactones are also classified as novel plant hormones that regulate several physiological processes other than germination, the use of autotrophic model plant species has allowed the identification of many actors involved in the strigolactone biosynthesis, perception, and signal transduction pathways. Nevertheless, many questions remain to be answered regarding the germination process of parasitic plants. For instance, how did parasitic plants evolve to germinate in response to a wide variety of molecules, while autotrophic plants do not? What particular features are associated with their lack of spontaneous germination? In this review, we attempt to illustrate to what extent conclusions from research into strigolactones could be applied to better understand the biology of parasitic plants.