Localization and Composition of Fructans in Stem and Rhizome of Agave tequilana Weber var. azul

The agavins (Agave carbohydrates) story

Fructans, are carbohydrates defined as fructose-based polymers with countable degree of polymerization (DP) ranging so far from DP3 to DP60. There are different types of fructans depending on their molecular arrangement. They are categorized as linear inulins and levans, neoseries of inulin and levan, branched graminans, and highly branched neofructans, so called agavins (Agave carbohydrates). It is worth to note that agavins are the most recently described type of fructans and they are also the most complex ones. The complexity of these carbohydrates is correlated to their various isomers and degree of polymerization range, which is correlated to their multifunctional application in industry and human health. Here, we narrate the story of the agavins' discovery. This included their chemical characterization, their benefits, biotechnological applications, and drawbacks over human health. Finally, a perspective of the study of agavins and their interactions with other metabolites through metabolomics is proposed.

β(2 → 1)-β(2 → 6) and β(2 → 1) fructans protect from impairment of intestinal tight junction's gene expression and attenuate human dendritic cell responses in a fructan-dependent fashion

β(2 → 1)-β(2 → 6) branched graminan-type fructans (GTFs) and β(2 → 1) linear fructans (ITFs) possess immunomodulatory properties and protect human intestinal barrier function, however the mechanisms underlying these effects are not well studied. Herein, GTFs and ITFs effects with different degree of polymerization (DP) values on tight junctions (TJs) genes CLDN-1, -2 and -3, CDH1, OCLN and TJP1 were studied in Caco-2 gut epithelial cells, under homeostatic and inflammatory conditions. Also, cytokine production in dendritic cells (DCs) was studied. Higher DP fructans decreased the expression of the pore forming CLDN-2. Higher DP GTFs enhanced CLDN-3, OCLN, and TJP-1. Fructans prevented mRNA dysregulation of CLDN-1, -2 and -3 induced by the barrier disruptors A23187 and deoxynivalenol in a fructan-type dependent fashion. The production of pro-inflammatory cytokines MCP-1/CCL2, MIP-1α/CCL3 and TNFα by DCs was also attenuated in a fructan-type dependent manner and was strongly attenuated by DCs cultured with medium of Caco-2 cells which were pre-exposed to fructans. Our data show that specific fructans have TJs and DCs modulating effects and contribute to gut homeostasis. This might serve to design effective dietary means to prevent intestinal inflammation.

β(2 → 1)-β(2 → 6) branched graminan-type fructans and β(2 → 1) linear fructans impact mucus-related and endoplasmic reticulum stress-related genes in goblet cells and attenuate inflammatory responses in a fructan dependent fashion

Dietary fibers such as fructans have beneficial effects on intestinal health but it is unknown whether they impact goblet cells (GCs). Here we studied the effects of inulin-type fructans (ITFs) and graminan-type fructans (GTFs) with different molecular weights on mucus- and endoplasmic reticulum (ER) stress-related genes in intestinal GCs. To that end, GCs were incubated in the presence of ITFs or GTFs, or ITFs and GTFs + TNFα or the N-glycosylation inhibitor tunicamycin (Tm). IL-8 production by GCs was studied as a marker of inflammation. Effects between ITFs and GTFs were compared. We found a beneficial impact of GTFs especially on the expression of RETNLB. GTF II protects from the TNFα-induced gene expression dysregulation of MUC2, TFF3, GAL3ST2, and CHST5. Also, all the studied fructans prevented Tm-induced dysregulation of GAL3ST2. Interestingly, only the short chain fructans ITF I and GTF I have anti-inflammatory properties on GCs. All the studied fructans except ITF I decreased the expression of the ER stress-related HSPA5 and XBP1. All these benefits were fructan-structure and chain length dependent. Our study contributes to a better understanding of chemical structure-dependent beneficial effects of ITFs and GTFs on gut barrier function, which could contribute to prevention of gut inflammatory disorders.

HPTLC-based fingerprinting: An alternative approach for fructooligosaccharides metabolism profiling

Fructans are categorized as fructose-based metabolites with no more than one glucose in their structure. Agave species possess a mixture of linear and ramified fructans with different degrees of polymerization. Among them, fructooligosaccharides are fructans with low degree of polymerization which might be approachable by high performance thin layer chromatography (HPTLC). Thus, this study used two emblematic Agave species collected at different ages as models to explore the feasibility of HPTLC-based fingerprinting to characterize fructooligosaccharides (FOS) production, accumulation, and behavior through time. To do so, high performance anion exchange was also used as analytical reference to determine the goodness and robustness of HPTLC data. The multivariate data analysis showed separation of samples dictated by species and age effects detected by both techniques. Moreover, linear correlations between the increase of the age in agave and their carbohydrate fraction was established in both species by both techniques. Oligosaccharides found to be correlated to species and age factors, these suggest changes in specific carbohydrate metabolism enzymes. Thus, HPTLC was proven as a complementary or stand-alone fingerprinting platform for fructooligosaccharides characterization in biological mixtures. However, the type of derivatizing reagent and the extraction color channel determined the goodness of the model used to scrutinize agavin fructooligosaccharides (aFOS).

Micropropagation of Seed-Derived Clonal Lines of the Endangered Agave marmorata Roezl and Their Compatibility with Endophytes

Simple Summary

The wild Agave marmorata Roezl has been classified as an endangered species. Extracting these plants from the forest for commercial purposes and long maturation periods of close to 30 years have contributed to their loss. A. marmorata interacts with pollinators and other Agaves species to maintain genetic variability. Thus, the conservation and restoration of the agave ecosystem is an ecological challenge. Typically, agave micropropagation use meristem or leaves as explants to rapidly produce uniform agave plants in age and size on a large scale leading to homogeneous plantations. However, introducing these clones to the field reduces genetic variability. This study evaluated in vitro micropropagation of A. marmorata from seeds to generate clonal lines. The selected seedlings exhibited variations in multiplication capacity and stable tissue formation. Variations in clonal lines could be exploited to produce high-quality plants with different capacities, such as faster propagation, enhanced stress adaptation, and continued growth under nutrient limitation conditions, consequently maintaining genetic variability. Furthermore, some clonal lines were inoculated with four endophytic bacteria to identify other differences among these plants, including endophyte-host compatibility. Variable responses to inoculation were observed among clonal lines. We found that Achromobacter xylosoxidans was compatible, unlike Enterobacter cloacae which caused plant death.

Abstract

A. marmorata is the raw material used for tepextate mescal production but is classified as an endangered species. In the present study, we obtain and multiply clonal lines of Agave marmorata Roezl by selecting seedlings derived from seeds. Ten seedlings from two lots of 400 germinated seeds were selected for axillary bud proliferation induced by BAP 5 mg/L in vitamin-free Murashige and Skoog’s medium. Differences in shoot numbers, heights and senescent tissue formation were observed. Notably, the AM32 line formed 84 shoots and presented low senescent tissue after 60 d of culture. We also selected the AM31 and AM33 clonal lines. Four-month shoots were extracted with 80% methanol in water to determine the total content of saponins, flavonoids, and phenolic acids and compare the three clonal lines. Some bioactive molecules were identified using HPLC techniques and MALDI-TOF mass spectrometry none showed significant differences in content. Additionally, plants derived from the clonal lines were inoculated with four endophytic bacteria. Among these, Achromobacter xylosoxidans supported plant growth of AM32. A notable effect of plant death was observed after inoculation with Enterobacter cloacae, an endophyte of A. tequilana. Additionally, Pseudomonas aeruginosa, an endophyte from A. marmorata, reduced biomass. Our results demonstrate the incompatibility of A. marmorata to E. cloacae and specialization between the host plant and its endophytes. The compatibility of the plant-endophyte could be exploited to boost the establishment and stability of mutualisms to benefit plant development, stress tolerance and pathogen resistance. The differences in multiplication capacity, stable tissue formation, and endophyte biotization responses may indicate genetic variability. Clonal selection and micropropagation from seed-derived plants could contribute to conserving the endangered A. marmorata plant for reforestation in their natural habitats, thus, assuring mass propagation for sustainable industrial production of mescal, bioactive compounds, and prebiotics.

Evidence for Light and Tissue Specific Regulation of Genes Involved in Fructan Metabolism in Agave tequilana

Plant Glycoside Hydrolase Family 32 (PGHF32) contains the fructosyltransferases and fructan exohydrolase enzymes responsible for fructan metabolism, in addition to closely related vacuolar and cell wall acid invertases. Agave species produce complex and dynamic fructan molecules (agavins) requiring 4 different fructosyltransferase activities (1-SST, 1-FFT, 6G-FFT and 6-SFT) for their synthesis. Combined analysis of RNAseq and genome data for A. tequilana led to the characterization of the genes encoding 3 fructosyltransferases for this species and support the hypothesis that no separate 6-SFT type enzyme exists in A. tequilana, suggesting that at least one of the fructosyltransferases identified may have multiple enzymatic activities. Structures for PGHF32 genes varied for A. tequilana and between other plant species but were conserved for different enzyme types within a species. The observed patterns are consistent with the formation of distinct gene structures by intron loss. Promoter analysis of the PGHF32 genes identified abundant putative regulatory motifs for light regulation and tissue-specific expression, and these regulatory mechanisms were confirmed experimentally for leaf tissue. Motifs for phytohormone response, carbohydrate metabolism and dehydration responses were also uncovered. Based on the regulatory motifs, full-length cDNAs for MYB, GATA, DOF and GBF transcription factors were identified and their phylogenetic distribution determined by comparison with other plant species. In silico expression analysis for the selected transcription factors revealed both tissue-specific and developmental patterns of expression, allowing candidates to be identified for detailed analysis of the regulation of fructan metabolism in A. tequilana at the molecular level.

Image to insight: exploring natural products through mass spectrometry imaging

Covering: 2017 to 2022Mass spectrometry imaging (MSI) has become a mature molecular imaging technique that is well-matched for natural product (NP) discovery. Here we present a brief overview of MSI, followed by a thorough discussion of different MSI applications in NP research. This review will mainly focus on the recent progress of MSI in plants and microorganisms as they are the main producers of NPs. Specifically, the opportunity and potential of combining MSI with other imaging modalities and stable isotope labeling are discussed. Throughout, we focus on both the strengths and weaknesses of MSI, with an eye on future improvements that are necessary for the progression of MSI toward routine NP studies. Finally, we discuss new areas of research, future perspectives, and the overall direction that the field may take in the years to come.

β(2→1) chicory and β(2→1)-β(2→6) agave fructans protect the human intestinal barrier function in vitro in a stressor-dependent fashion

Dietary fibers such as fructans can protect the intestinal epithelial barrier integrity, but the mechanisms underlying this protection are not completely understood. We aimed to study the protective effect of β(2→1)-β(2→6) branched graminan-type fructans (GTFs) on gut epithelial barrier function that was disrupted by three different agents which impact the barrier function via different cellular mechanisms. The effects of GTFs were compared with those of linear β(2→1) inulin-type fructans (ITFs). T84 intestinal epithelial monolayers were incubated with GTFs and ITFs. Afterwards, the monolayers were challenged with the barrier disruptors calcium ionophore A23187, 12-myristate 13-acetate (PMA) and deoxynivalenol (DON). Transepithelial resistance was measured with an electric cell-substrate impedance sensing system. All fructans studied prevented the barrier disruption induced by A23187. ITF II protected from the disruptive effects of PMA. However, none of the studied fructans influenced the disruption induced by DON. As a measure of disruption-induced inflammation, interleukin-8 (IL-8) production by the intestinal epithelium was determined by ELISA. The production of IL-8 induced by A23187 was decreased by all fructans, whereas IL-8 production induced by DON decreased only upon pre-treatment with ITF II. None of the studied fructans prevented PMA induced IL-8 production. GTFs just like ITFs can influence the barrier function and inflammatory processes in gut epithelial cells in a structure-dependent fashion. These distinct protective effects are dependent on the different signaling pathways that lead to gut barrier disruption.