Enrique Ramírez-Chávez

Antimicrobial properties of alkamides present in flavouring plants traditionally used in Mesoamerica : affinin and capsaicin

The bioactive amides affinin and capsaicin isolated respectively from Heliopsis longipes roots and Capsicum spp fruits, were assayed for activity against Escherichia coli, Pseudomonas solanacearum, Bacillus subtilis and Saccharomyces cerevisicae suspension cultures. The alkamide affinin inhibited growth of E. coli and S. cerevisiae at concentrations as low as 25 microg/ml. Higher concentrations of affinin were necessary to inhibit growth of P. solanacearum and B. subtilis. However. high concentrations of capsaicin only retarded the growth of E. coli and P. solanacearum, whereas growth of B. subtilis was strongly inhibited and that of S. cerevisiae was initially enhanced. Results are discussed in relation to previous reports concerning crude extract and to the molecular structures of the bioactive compounds.

How Plants Sense Wounds: Damaged-Self Recognition Is Based on Plant-Derived Elicitors and Induces Octadecanoid Signaling

Background Animal-derived elicitors can be used by plants to detect herbivory but they function only in specific insect–plant interactions. How can plants generally perceive damage caused by herbivores? Damaged-self recognition occurs when plants perceive molecular signals of damage: degraded plant molecules or molecules localized outside their original compartment. Methodology/Principal Findings Flame wounding or applying leaf extract or solutions of sucrose or ATP to slightly wounded lima bean (Phaseolus lunatus) leaves induced the secretion of extrafloral nectar, an indirect defense mechanism. Chemically related molecules that would not be released in high concentrations from damaged plant cells (glucose, fructose, salt, and sorbitol) did not elicit a detectable response, excluding osmotic shock as an alternative explanation. Treatments inducing extrafloral nectar secretion also enhanced endogenous concentrations of the defense hormone jasmonic acid (JA). Endogenous JA was also induced by mechanically damaging leaves of lima bean, Arabidopsis, maize, strawberry, sesame and tomato. In lima bean, tomato and sesame, the application of leaf extract further increased endogenous JA content, indicating that damaged-self recognition is taxonomically widely distributed. Transcriptomic patterns obtained with untargeted 454 pyrosequencing of lima bean in response to flame wounding or the application of leaf extract or JA were highly similar to each other, but differed from the response to mere mechanical damage. We conclude that the amount or concentration of damaged-self signals can quantitatively determine the intensity of the wound response and that the full damaged-self response requires the disruption of many cells. Conclusions/Significance Numerous compounds function as JA-inducing elicitors in different plant species. Most of them are, contain, or release, plant-derived molecular motifs. Damaged-self recognition represents a taxonomically widespread mechanism that contributes to the perception of herbivore feeding by plants. This strategy is independent of insect-derived elicitors and, therefore, allows plants to maintain evolutionary control over their interaction with herbivores.

The xipotl Mutant of Arabidopsis Reveals a Critical Role for Phospholipid Metabolism in Root System Development and Epidermal Cell Integrity

Phosphocholine (PCho) is an essential metabolite for plant development because it is the precursor for the biosynthesis of phosphatidylcholine, which is the major lipid component in plant cell membranes. The main step in PCho biosynthesis in Arabidopsis thaliana is the triple, sequential N-methylation of phosphoethanolamine, catalyzed by S-adenosyl-l-methionine:phosphoethanolamine N-methyltransferase (PEAMT). In screenings performed to isolate Arabidopsis mutants with altered root system architecture, a T-DNA mutagenized line showing remarkable alterations in root development was isolated. At the seedling stage, the mutant phenotype is characterized by a short primary root, a high number of lateral roots, and short epidermal cells with aberrant morphology. Genetic and biochemical characterization of this mutant showed that the T-DNA was inserted at the At3g18000 locus (XIPOTL1), which encodes PEAMT (XIPOTL1). Further analyses revealed that inhibition of PCho biosynthesis in xpl1 mutants not only alters several root developmental traits but also induces cell death in root epidermal cells. Epidermal cell death could be reversed by phosphatidic acid treatment. Taken together, our results suggest that molecules produced downstream of the PCho biosynthesis pathway play key roles in root development and act as signals for cell integrity.

Alkamides isolated from plants promote growth and alter root development in Arabidopsis.

To date, several classes of hormones have been described that influence plant development, including auxins, cytokinins, ethylene, and, more recently, brassinosteroids. However, it is known that many fungal and bacterial species produce substances that alter plant growth that, if naturally present in plants, might represent novel classes of plant growth regulators. Alkamides are metabolites widely distributed in plants with a broad range of biological activities. In this work, we investigated the effects of affinin, an alkamide naturally occurring in plants, and its derivates, N-isobutyl-2E-decenamide and N-isobutyl-decanamide, on plant growth and early root development in Arabidopsis. We found that treatments with affinin in the range of 10-6 to 10-4 m alter shoot and root biomass production. This effect correlated with alteration on primary root growth, lateral root formation, and root hair elongation. Low concentrations of affinin (7 × 10-6–2.8 × 10-5 m) enhanced primary root growth and root hair elongation, whereas higher concentrations inhibited primary root growth that related with a reduction in cell proliferating activity and cell elongation. N-isobutyl-2E-decenamide and N-isobutyl-decanamide were found to stimulate root hair elongation at concentrations between 10-8 to 10-7 m. Although the effects of alkamides were similar to those produced by auxins on root growth and cell parameters, the ability of the root system to respond to affinin was found to be independent of auxin signaling. Our results suggest that alkamides may represent a new group of plant growth promoting substances with significant impact on root development and opens the possibility of using these compounds for improved plant production.

Purely olefinic alkamnides in Heliopsis longipes and Acmella (Spilanthes) oppositifolia

Abstract Acmella (Spilanthes) oppositifolia and Heliopsis longipes are collected from the wild and used as medicinal, flavouring and insecticidal plants. These species contain purely olefinic alkamides (not containing acetylenic bonds) with affinin 1 as the main lipidic component and N -2-methylbutyldeca-2 E ,6 Z ,8 E -trienamide 2 , in lower quantities. In A. oppositifolia N -isobutyl-dodeca-2 E ,4 E ,8 Z ,10 E -tetraenamide 3 was detected with the above mentioned alkamides. For this species the same components can be found in roots and aerial parts. Heliopsis longipes alkamides are present only in roots. A comparison of the purely olefinic alkamide structures observed in the Heliantheae is discussed briefly.

Cytokinin receptors are involved in alkamide regulation of root and shoot development in Arabidopsis.

Alkamides and N-acilethanolamides are a class of lipid compounds related to animal endocannabinoids of wide distribution in plants. We investigated the structural features required for alkamides to regulate plant development by comparing the root responses of Arabidopsis (Arabidopsis thaliana) seedlings to a range of natural and synthetic compounds. The length of the acyl chain and the amide moiety were found to play a crucial role in their biological activity. From the different compounds tested, N-isobutyl decanamide, a small saturated alkamide, was found to be the most active in regulating primary root growth and lateral root formation. Proliferative-promoting activity of alkamide treatment was evidenced by formation of callus-like structures in primary roots, ectopic blades along petioles of rosette leaves, and disorganized tumorous tissue originating from the leaf lamina. Ectopic organ formation by N-isobutyl decanamide treatment was related to altered expression of the cell division marker CycB1:uidA and an enhanced expression of the cytokinin-inducible marker ARR5:uidA both in roots and in shoots. The involvement of cytokinins in mediating the observed activity of alkamides was tested using Arabidopsis mutants lacking one, two, or three of the putative cytokinin receptors CRE1, AHK2, and AHK3. The triple cytokinin receptor mutant was insensitive to N-isobutyl decanamide treatment, showing absence of callus-like structures in roots, the lack of lateral root proliferation, and absence of ectopic outgrowths in leaves under elevated levels of this alkamide. Taken together our results suggest that alkamides and N-acylethanolamides may belong to a class of endogenous signaling compounds that interact with a cytokinin-signaling pathway to control meristematic activity and differentiation processes during plant development.

Alkamides Activate Jasmonic Acid Biosynthesis and Signaling Pathways and Confer Resistance to Botrytis cinerea in Arabidopsis thaliana

Alkamides are fatty acid amides of wide distribution in plants, structurally related to N-acyl-L-homoserine lactones (AHLs) from Gram-negative bacteria and to N- acylethanolamines (NAEs) from plants and mammals. Global analysis of gene expression changes in Arabidopsis thaliana in response to N-isobutyl decanamide, the most highly active alkamide identified to date, revealed an overrepresentation of defense-responsive transcriptional networks. In particular, genes encoding enzymes for jasmonic acid (JA) biosynthesis increased their expression, which occurred in parallel with JA, nitric oxide (NO) and H2O2 accumulation. The activity of the alkamide to confer resistance against the necrotizing fungus Botrytis cinerea was tested by inoculating Arabidopsis detached leaves with conidiospores and evaluating disease symptoms and fungal proliferation. N-isobutyl decanamide application significantly reduced necrosis caused by the pathogen and inhibited fungal proliferation. Arabidopsis mutants jar1 and coi1 altered in JA signaling and a MAP kinase mutant (mpk6), unlike salicylic acid- (SA) related mutant eds16/sid2-1, were unable to defend from fungal attack even when N-isobutyl decanamide was supplied, indicating that alkamides could modulate some necrotrophic-associated defense responses through JA-dependent and MPK6-regulated signaling pathways. Our results suggest a role of alkamides in plant immunity induction.

Acmella radicans var. radicans: In vitro culture establishment and alkamide content

SummaryAcmella radicans var. radicans propagation was established in vitro. This plant belongs to the Asteraceae from which some species are known for their insecticide, fungicide and antibacterial activity. The complete Murashige and Skoog (MS) medium was the best in assisting seed germination. In order to obtain shoots in vitro, a complete MS medium and half-strength MS medium were assayed with explants from leaves, nodes, and internodes. The best medium for shoot production was the half-strength MS medium with no addition of plant growth regulators, and the highest shoot propagation was from single-node explants. Regeneration of roots on shoot explants in the medium was obtained without the addition of growth regulators. Of the plantlets that were acclimated, 90% of them were obtained from rooted shoots with completely expanded leaves. The alkamide content was evaluated for each tissue and the higher concentration was observed in flower heads. The main alkamides present in the leaves and the flower heads were N-(2-phenylethyl)-2Z,4E-octadienamide and 3-phenyl-N-(2-phenylethyl)-2-propenamide. This study describes the methodology for the establishment and propagation of Acmella radicans in vitro and the evaluation of different tissue alkamide contents in vitro and in the field.

Circulating profiling reveals the effect of a polyunsaturated fatty acid-enriched diet on common microRNAs.

BACKGROUND Consumption of long-chain polyunsaturated fatty acids (PUFAs), which are abundant in seafood and nuts, ameliorates components of the metabolic syndrome. Circulating microRNAs (miRNAs) have demonstrated to be valuable biomarkers of metabolic diseases. Here, we investigated whether a sustained nuts-enriched diet can lead to changes in circulating miRNAs, in parallel to the dietary modification of fatty acids (FAs). METHODS AND RESULTS The profile of 192 common miRNAs was assessed (TaqMan low-density arrays) in plasma from 10 healthy women before and after an 8-week trial with a normocaloric diet enriched with PUFAs (30 g/day of almonds and walnuts). The most relevant miRNAs were validated in an extended sample of 30 participants (8 men and 22 women). Adiponectin was measured by immunoassay and FAs by gas liquid chromatography coupled to mass spectrometry. The percentage of both ω-3 (P=.01) and ω-6 (P=.029) PUFAs of dietary origin (as inferred from plasma FA concentrations) increased, whereas saturated FAs decreased (P=.0008). Concomitantly with changes in circulating FAs, several miRNAs were modified by treatment, including decreased miR-328, miR-330-3p, miR-221 and miR-125a-5p, and increased miR-192, miR-486-5p, miR-19b, miR-106a, miR-769-5p, miR-130b and miR-18a. Interestingly, miR-106a variations in plasma correlated with changes in PUFAs, while miR-130b (r=0.58, P=.003) and miR-221 (r=0.46, P=.03) reflected changes in C-reactive protein. The dietary modulation of miR-125a-5p mirrored changes in fasting triglycerides (r=-0.44, P=.019) and increased adiponectin (r=0.43, P=.026). CONCLUSION Dietary FAs (as inferred from plasma FA concentration) are linked to changes in circulating miRNAs, which may be modified by a PUFAs-enriched diet.

Montanoa tomentosa glandular trichomes containing kaurenoic acids chemical profile and distribution

Montanoa tomentosa has been used in traditional medicine in Mexico to treat diverse female health disorders; it is particularly useful in inducing childbirth. Microscopic analysis of leaf surfaces of M. tomentosa revealed the presence of glandular trichomes. The chemical profile and distribution of glandular trichomes from different developmental stages of M. tomentosa leaves were investigated. Two diterpenic acids, kaurenoic and grandiflorenic were detected in glandular trichomes through the glandular microsampling technique and GC/MS analysis. In the glandular trichomes of the leaves also up to twenty-six volatile terpenes were identified, where beta-eudesmol and valencene were the most abundant terpenes.