Arthrobacter sp. UMCV2, and its compound N,N-dimethylhexadecilamine promote nodulation in Medicago truncatula by Sinorhizobium medicae.

The actinobacterium Arthrobacter sp. UMCV2 promotes plant growth through the emission of N,N-dimethylhexadecilamine (DMHDA). The Medicago-Sinorhizobium nodulation has been employed to study symbiotic nitrogen fixation by rhizobia in nodulating Fabaceae. Herein, we isolated three Sinorhizobium medicae strains that were used to induce nodules in Medicago truncatula. The co-inoculation of M. truncatula with Arthrobacter sp. strain UMCV2 produced a higher number of effective nodules than inoculation with only Sinorhizobium strains. Similarly, the exposure of inoculated M. truncatula to DMHDA produced a greater number of effective nodules compared to non-exposed plants. Thus, we conclude that Arthrobacter sp. UMCV2 promotes nodulation, and propose that this effect is produced, at least partly, via DMHDA emission.

Worldwide study of the taste of bitter medicines and their modifiers.

The bitter taste of medicines hinders patient compliance, but not everyone experiences these difficulties because people worldwide differ in their bitterness perception. To better understand how people from diverse ancestries perceive medicines and taste modifiers, 338 adults, European and recent US and Canada immigrants from Asia, South Asia, and Africa, rated the bitterness intensity of taste solutions on a 100-point generalized visual analog scale and provided a saliva sample for genotyping. The taste solutions were five medicines, tenofovir alafenamide (TAF), moxifloxacin, praziquantel, amodiaquine, and propylthiouracil (PROP), and four other solutions, TAF mixed with sucralose (sweet, reduces bitterness) or 6-methylflavone (tasteless, reduces bitterness), sucralose alone, and sodium chloride alone. Bitterness ratings differed by ancestry for two of the five drugs (amodiaquine and PROP) and for TAF mixed with sucralose. Genetic analysis showed that people with variants in one bitter receptor variant gene (TAS2R38) reported PROP was more bitter than did those with a different variant (p= 7.6e-19) and that people with either an RIMS2 or a THSD4 genotype found sucralose more bitter than did others (p=2.6e-8, p=7.9e-11, resp.). Our findings may help guide the formulation of bad-tasting medicines to meet the needs of those most sensitive to them.

Taste loss as a distinct symptom of COVID-19: a systematic review and meta-analysis.

Chemosensory scientists have been skeptical that reports of COVID-19 taste loss are genuine, in part because before COVID-19 taste loss was rare and often confused with smell loss. Therefore, to establish the predicted prevalence rate of taste loss in COVID-19 patients, we conducted a systematic review and meta-analysis of 376 papers published in 2020-2021, with 235 meeting all inclusion criteria. Drawing on previous studies and guided by early meta-analyses, we explored how methodological differences (direct vs. self-report measures) may affect these estimates. We hypothesized that direct measures of taste are at least as sensitive as those obtained by self-report and that the preponderance of evidence confirms taste loss is a symptom of COVID-19. The meta-analysis showed that, among 138,015 COVID-19-positive patients, 36.62% reported taste dysfunction (95% confidence interval: 33.02%-40.39%), and the prevalence estimates were slightly but not significantly higher from studies using direct (n = 15) versus self-report (n = 220) methodologies (Q = 1.73, df = 1, P = 0.1889). Generally, males reported lower rates of taste loss than did females, and taste loss was highest among middle-aged adults. Thus, taste loss is likely a bona fide symptom of COVID-19, meriting further research into the most appropriate direct methods to measure it and its underlying mechanisms.

Identification of a xyloglucan beta-xylopyranosyltransferase from Vaccinium corymbosum.

Plant cell walls contain the hemicellulose xyloglucan, whose fine structure may vary depending on cell type, tissue, and/or plant species. Most but not all of the glycosyltransferases involved in the biosynthesis of xyloglucan sidechains have been identified. Here, we report the identification of several functional glycosyltransferases from blueberry (Vaccinium corymbosum bluecrop). Among those transferases is a hitherto elusive Xyloglucan:Beta-xylosylTransferase (XBT). Heterologous expression of VcXBT in the Arabidopsis thaliana double mutant mur3 xlt2, where xyloglucan consists only of an unsubstituted xylosylated glucan core structure, results in the production of the xylopyranose-containing "U" sidechain as characterized by mass spectrometry, glycosidic linkage, and NMR analysis. The introduction of the additional xylopyranosyl residue rescues the dwarfed phenotype of the untransformed Arabidopsis mur3 xlt2 mutant to wild-type height. Structural protein analysis using Alphafold of this and other related xyloglucan glycosyltransferase family 47 proteins not only identifies potential domains that might influence the regioselectivity of these enzymes but also gives hints to specific amino acids that might determine the donor-substrate specificity of these glycosyltransferases.

Cross-Talk between Iron Deficiency Response and Defense Establishment in Plants.

Plants are at risk of attack by various pathogenic organisms. During pathogenesis, microorganisms produce molecules with conserved structures that are recognized by plants that then initiate a defense response. Plants also experience iron deficiency. To address problems caused by iron deficiency, plants use two strategies focused on iron absorption from the rhizosphere. Strategy I is based on rhizosphere acidification and iron reduction, whereas Strategy II is based on iron chelation. Pathogenic defense and iron uptake are not isolated phenomena: the antimicrobial phenols are produced by the plant during defense, chelate and solubilize iron; therefore, the production and secretion of these molecules also increase in response to iron deficiency. In contrast, phytohormone jasmonic acid and salicylic acid that induce pathogen-resistant genes also modulate the expression of genes related to iron uptake. Iron deficiency also induces the expression of defense-related genes. Therefore, in the present review, we address the cross-talk that exists between the defense mechanisms of both Systemic Resistance and Systemic Acquired Resistance pathways and the response to iron deficiency in plants, with particular emphasis on the regulation genetic expression.

A large-scale forward genetic screen for maize mutants with altered lignocellulosic properties.

The development of efficient pipelines for the bioconversion of grass lignocellulosic feedstocks is challenging due to the limited understanding of the molecular mechanisms controlling the synthesis, deposition, and degradation of the varying polymers unique to grass cell walls. Here, we describe a large-scale forward genetic approach resulting in the identification of a collection of chemically mutagenized maize mutants with diverse alterations in their cell wall attributes such as crystalline cellulose content or hemicellulose composition. Saccharification yield, i.e. the amount of lignocellulosic glucose (Glc) released by means of enzymatic hydrolysis, is increased in two of the mutants and decreased in the remaining six. These mutants, termed candy-leaf (cal), show no obvious plant growth or developmental defects despite associated differences in their lignocellulosic composition. The identified cal mutants are a valuable tool not only to understand recalcitrance of grass lignocellulosics to enzymatic deconstruction but also to decipher grass-specific aspects of cell wall biology once the genetic basis, i.e. the location of the mutation, has been identified.

Global population genetics and diversity in the TAS2R bitter taste receptor family.

Bitter taste receptors (TAS2Rs) are noted for their role in perception, and mounting evidence suggests that they mediate responses to compounds entering airways, gut, and other tissues. The importance of these roles suggests that TAS2Rs have been under pressure from natural selection. To determine the extent of variation in TAS2Rs on a global scale and its implications for human evolution and behavior, we analyzed patterns of diversity in the complete 25 gene repertoire of human TAS2Rs in ∼2,500 subjects representing worldwide populations. Across the TAS2R family as a whole, we observed 721 single nucleotide polymorphisms (SNPs) including 494 nonsynonymous SNPs along with 40 indels and gained and lost start and stop codons. In addition, computational predictions identified 169 variants particularly likely to affect receptor function, making them candidate sources of phenotypic variation. Diversity levels ranged widely among loci, with the number of segregating sites ranging from 17 to 41 with a mean of 32 among genes and per nucleotide heterozygosity (π) ranging from 0.02% to 0.36% with a mean of 0.12%. F ST ranged from 0.01 to 0.26 with a mean of 0.13, pointing to modest differentiation among populations. Comparisons of observed π and F ST values with their genome wide distributions revealed that most fell between the 5th and 95th percentiles and were thus consistent with expectations. Further, tests for natural selection using Tajima's D statistic revealed only two loci departing from expectations given D's genome wide distribution. These patterns are consistent with an overall relaxation of selective pressure on TAS2Rs in the course of recent human evolution.

Reduction of Instrumentation-Related Spine Surgical Site Infections After Optimization of Surgical Techniques. A Single Center Retrospective Analysis.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: Although surgical risk factors for developing spine surgical site infections (S-SSI) have been identified, the impact of such knowledge in its prevention has not been demonstrated. METHODS: We evaluated in 500 patients undergoing spine surgery between 2011 and 2019 at Hospital 12 de Octubre the changes in S-SSI rates over time. Surgical variables independently related to S-SSI were analyzed by univariate and multivariate analysis using binary logistic regression models. A case-control sub-analysis (1:4), matched by the surgical variables identified in the overall cohort was also performed. RESULTS: Twenty cases of S-SSI were identified (4%), with a significant decrease in the incidence rate across consecutive time periods (6.6% [2011-2014] vs .86% [2015-2019]; P-value <.0001)). Multivariate analysis identified arthrodesis involving sacral levels (odds ratio [OR]: 2.57; 95% confidence interval [95%CI]: 1.02-6.47; P-value = .044) and instrumentation over 4-8 vertebrae (OR: 2.82; 95%CI: 1.1-7.1; P-value = .027) as independent risk factors for S-SSI. The reduction in the incidence of S-SSI concurred temporally with a reduction in instrumentations involving 4-8 vertebrae (55% vs 21.8%; P-value <.0001) and sacral vertebrae (46.9% vs 24.6%; P-value <.0001) across both periods. The case-control analysis matched by these surgical variables failed to identify other factors independently related to the occurrence of S-SSI. CONCLUSIONS: Spinal fusion of more than 4 levels and the inclusion of sacral levels were independently related to the risk of S-SSI. Optimization of surgical techniques by reducing these two types of instrumentation could significantly reduce S-SSI rates.

Emerging Roles of ß-Glucanases in Plant Development and Adaptative Responses.

Plant ß-glucanases are enzymes involved in the synthesis, remodelling and turnover of cell wall components during multiple physiological processes. Based on the type of the glycoside bond they cleave, plant ß-glucanases have been grouped into three categories: (i) ß-1,4-glucanases degrade cellulose and other polysaccharides containing 1,4-glycosidic bonds to remodel and disassemble the wall during cell growth. (ii) ß-1,3-glucanases are responsible for the mobilization of callose, governing the symplastic trafficking through plasmodesmata. (iii) ß-1,3-1,4-glucanases degrade mixed linkage glucan, a transient wall polysaccharide found in cereals, which is broken down to obtain energy during rapid seedling growth. In addition to their roles in the turnover of self-glucan structures, plant ß-glucanases are crucial in regulating the outcome in symbiotic and hostile plant-microbe interactions by degrading non-self glucan structures. Plants use these enzymes to hydrolyse ß-glucans found in the walls of microbes, not only by contributing to a local antimicrobial defence barrier, but also by generating signalling glucans triggering the activation of global responses. As a counterpart, microbes developed strategies to hijack plant ß-glucanases to their advantage to successfully colonize plant tissues. This review outlines our current understanding on plant ß-glucanases, with a particular focus on the latest advances on their roles in adaptative responses.

Taste loss as a distinct symptom of COVID-19: a systematic review and meta-analysis.

Chemosensory scientists have been skeptical that reports of COVID-19 taste loss are genuine, in part because before COVID-19 taste loss was rare and often confused with smell loss. Therefore, to establish the predicted prevalence rate of taste loss in COVID-19 patients, we conducted a systematic review and meta-analysis of 376 papers published in 2020-2021, with 241 meeting all inclusion criteria. Drawing on previous studies and guided by early meta-analyses, we explored how methodological differences (direct vs. self-report measures) may affect these estimates. We hypothesized that direct measures of taste are at least as sensitive as those obtained by self-report and that the preponderance of evidence confirms taste loss is a symptom of COVID-19. The meta-analysis showed that, among 138,897 COVID-19-positive patients, 39.2% reported taste dysfunction (95% confidence interval: 35.34%-43.12%), and the prevalence estimates were slightly but not significantly higher from studies using direct (n = 18) versus self-report (n = 223) methodologies (Q = 0.57, df = 1, P = 0.45). Generally, males reported lower rates of taste loss than did females, and taste loss was highest among middle-aged adults. Thus, taste loss is likely a bona fide symptom of COVID-19, meriting further research into the most appropriate direct methods to measure it and its underlying mechanisms.

Worldwide diversity, association potential, and natural selection in the superimposed taste genes, CD36 and GNAT3.

CD36 and GNAT3 mediate taste responses, with CD36 acting as a lipid detector and GNAT3 acting as the α subunit of gustducin, a G protein governing sweet, savory, and bitter transduction. Strikingly, the genes encoding CD36 and GNAT3 are genomically superimposed, with CD36 completely encompassing GNAT3. To characterize genetic variation across the CD36-GNAT3 region, its implications for phenotypic diversity, and its recent evolution, we analyzed from ~2,500 worldwide subjects sequenced by the 1000 Genomes Project (1000GP). CD36-GNAT3 harbored extensive diversity including 8,688 single-nucleotide polymorphisms (SNPs), 414 indels, and other complex variants. Sliding window analyses revealed that nucleotide diversity and population differentiation across CD36-GNAT3 were consistent with genome-wide trends in the 1000GP (π = 0.10%, P = 0.64; FST = 9.0%, P = 0.57). In addition, functional predictions using SIFT and PolyPhen-2 identified 60 variants likely to alter protein function, and they were in weak linkage disequilibrium (r2 < 0.17), suggesting their effects are largely independent. However, the frequencies of predicted functional variants were low (P¯ = 0.0013), indicating their contributions to phenotypic variance on population scales are limited. Tests using Tajima's D statistic revealed that pressures from natural selection have been relaxed across most of CD36-GNAT3 during its recent history (0.39 < P < 0.67). However, CD36 exons showed signs of local adaptation consistent with prior reports (P < 0.035). Thus, CD36 and GNAT3 harbor numerous variants predicted to affect taste sensitivity, but most are rare and phenotypic variance on a population level is likely mediated by a small number of sites.

Taste loss as a distinct symptom of COVID-19: A systematic review and meta-analysis.

Chemosensory scientists have been skeptical that reports of COVID-19 taste loss are genuine, in part because before COVID-19, taste loss was rare and often confused with smell loss. Therefore, to establish the predicted prevalence rate of taste loss in COVID-19 patients, we conducted a systematic review and meta-analysis of 376 papers published in 2020-2021, with 241 meeting all inclusion criteria. Additionally, we explored how methodological differences (direct vs. self-report measures) may affect these estimates. We hypothesized that direct prevalence measures of taste loss would be the most valid because they avoid the taste/smell confusion of self-report. The meta-analysis showed that, among 138,897 COVID-19-positive patients, 39.2% reported taste dysfunction (95% CI: 35.34-43.12%), and the prevalence estimates were slightly but not significantly higher from studies using direct (n = 18) versus self-report (n = 223) methodologies (Q = 0.57, df = 1, p = 0.45). Generally, males reported lower rates of taste loss than did females and taste loss was highest in middle-aged groups. Thus, taste loss is a bona fide symptom COVID-19, meriting further research into the most appropriate direct methods to measure it and its underlying mechanisms.

A mixed-linkage (1,3;1,4)-ß-D-glucan specific hydrolase mediates dark-triggered degradation of this plant cell wall polysaccharide.

The presence of mixed-linkage (1,3;1,4)-ß-d-glucan (MLG) in plant cell walls is a key feature of grass species such as cereals, the main source of calorie intake for humans and cattle. Accumulation of this polysaccharide involves the coordinated regulation of biosynthetic and metabolic machineries. While several components of the MLG biosynthesis machinery have been identified in diverse plant species, degradation of MLG is poorly understood. In this study, we performed a large-scale forward genetic screen for maize (Zea mays) mutants with altered cell wall polysaccharide structural properties. As a result, we identified a maize mutant with increased MLG content in several tissues, including adult leaves and senesced organs, where only trace amounts of MLG are usually detected. The causative mutation was found in the GRMZM2G137535 gene, encoding a GH17 licheninase as demonstrated by an in vitro activity assay of the heterologously expressed protein. In addition, maize plants overexpressing GRMZM2G137535 exhibit a 90% reduction in MLG content, indicating that the protein is not only required, but its expression is sufficient to degrade MLG. Accordingly, the mutant was named MLG hydrolase 1 (mlgh1). mlgh1 plants show increased saccharification yields upon enzymatic digestion. Stacking mlgh1 with lignin-deficient mutations results in synergistic increases in saccharification. Time profiling experiments indicate that wall MLG content is modulated during day/night cycles, inversely associated with MLGH1 transcript accumulation. This cycling is absent in the mlgh1 mutant, suggesting that the mechanism involved requires MLG degradation, which may in turn regulate MLGH1 gene expression.

Bitter taste receptors: Genes, evolution and health.

Bitter taste perception plays vital roles in animal behavior and fitness. By signaling the presence of toxins in foods, particularly noxious defense compounds found in plants, it enables animals to avoid exposure. In vertebrates, bitter perception is initiated by TAS2Rs, a family of G protein-coupled receptors expressed on the surface of taste buds. There, oriented toward the interior of the mouth, they monitor the contents of foods, drinks and other substances as they are ingested. When bitter compounds are encountered, TAS2Rs respond by triggering neural pathways leading to sensation. The importance of this role placed TAS2Rs under selective pressures in the course of their evolution, leaving signatures in patterns of gene gain and loss, sequence polymorphism, and population structure consistent with vertebrates' diverse feeding ecologies. The protective value of bitter taste is reduced in modern humans because contemporary food supplies are safe and abundant. However, this is not always the case. Some crops, particularly in the developing world, retain surprisingly high toxicity and bitterness remains an important measure of safety. Bitter perception also shapes health through its influence on preference driven behaviors such as diet choice, alcohol intake and tobacco use. Further, allelic variation in TAS2Rs is extensive, leading to individual differences in taste sensitivity that drive these behaviors, shaping susceptibility to disease. Thus, bitter taste perception occupies a critical intersection between ancient evolutionary processes and modern human health.

Objective Sensory Testing Methods Reveal a Higher Prevalence of Olfactory Loss in COVID-19-Positive Patients Compared to Subjective Methods: A Systematic Review and Meta-Analysis.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), has currently infected over 6.5 million people worldwide. In response to the pandemic, numerous studies have tried to identify the causes and symptoms of the disease. Emerging evidence supports recently acquired anosmia (complete loss of smell) and hyposmia (partial loss of smell) as symptoms of COVID-19, but studies of olfactory dysfunction show a wide range of prevalence from 5% to 98%. We undertook a search of Pubmed/Medline and Google Scholar with the keywords "COVID-19," "smell," and/or "olfaction." We included any study that quantified smell loss (anosmia and hyposmia) as a symptom of COVID-19. Studies were grouped and compared based on the type of method used to measure smell loss-subjective measures, such as self-reported smell loss, versus objective measures using rated stimuli-to determine if prevalence differed by method type. For each study, 95% confidence intervals (CIs) were calculated from point estimates of olfactory disturbances. We identified 34 articles quantifying anosmia as a symptom of COVID-19 (6 objective and 28 subjective), collected from cases identified from January 16 to April 30, 2020. The pooled prevalence estimate of smell loss was 77% when assessed through objective measurements (95% CI of 61.4-89.2%) and 44% with subjective measurements (95% CI of 32.2-57.0%). Objective measures are a more sensitive method to identify smell loss as a result of infection with SARS-CoV-2; the use of subjective measures, while expedient during the early stages of the pandemic, underestimates the true prevalence of smell loss.

Objective sensory testing methods reveal a higher prevalence of olfactory loss in COVID-19-positive patients compared to subjective methods: A systematic review and meta-analysis.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), has currently infected over 6.5 million people worldwide. In response to the pandemic, numerous studies have tried to identify causes and symptoms of the disease. Emerging evidence supports recently acquired anosmia (complete loss of smell) and hyposmia (partial loss of smell) as symptoms of COVID-19, but studies of olfactory dysfunction show a wide range of prevalence, from 5% to 98%. We undertook a search of Pubmed/Medline and Google Scholar with the keywords "COVID-19," "smell," and/or "olfaction." We included any study that quantified olfactory loss as a symptom of COVID-19. Studies were grouped and compared based on the type of method used to measure smell loss-subjective measures such as self-reported smell loss versus objective measures using rated stimuli-to determine if prevalence rate differed by method type. For each study, 95% confidence intervals (CIs) were calculated from point estimates of olfactory disturbance rates. We identified 34 articles quantifying anosmia as a symptom of COVID-19, collected from cases identified from January 16 to April 30, 2020. The pooled prevalence estimate of smell loss was 77% when assessed through objective measurements (95% CI of 61.4-89.2%) and 45% with subjective measurements (95% CI of 31.1-58.5%). Objective measures are a more sensitive method to identify smell loss as a result of infection with SARS-CoV-2; the use of subjective measures, while expedient during the early stages of the pandemic, underestimates the true prevalence of smell loss.

Bacterial Compound N,N-Dimethylhexadecylamine Modulates Expression of Iron Deficiency and Defense Response Genes in Medicago truncatula Independently of the Jasmonic Acid Pathway.

Plants face a variety of biotic and abiotic stresses including attack by microbial phytopathogens and nutrient deficiencies. Some bacterial volatile organic compounds (VOCs) activate defense and iron-deficiency responses in plants. To establish a relationship between defense and iron deficiency through VOCs, we identified key genes in the defense and iron-deprivation responses of the legume model Medicago truncatula and evaluated the effect of the rhizobacterial VOC N,N-dimethylhexadecylamine (DMHDA) on the gene expression in these pathways by RT-qPCR. DMHDA increased M. truncatula growth 1.5-fold under both iron-sufficient and iron-deficient conditions compared with untreated plants, whereas salicylic acid and jasmonic acid decreased growth. Iron-deficiency induced iron uptake and defense gene expression. Moreover, the effect was greater in combination with DMHDA. Salicylic acid, Pseudomonas syringae, jasmonic acid, and Botrytis cinerea had inhibitory effects on growth and iron response gene expression but activated defense genes. Taken together, our results showed that the VOC DMHDA activates defense and iron-deprivation pathways while inducing a growth promoting effect unlike conventional phytohormones, highlighting that DMHDA does not mimic jasmonic acid but induces an alternative pathway. This is a novel aspect in the complex interactions between biotic and abiotic stresses.

The volatile organic compound dimethylhexadecylamine affects bacterial growth and swarming motility of bacteria.

Bacteria have developed different intra- and inter-specific communication mechanisms that involve the production, release, and detection of signaling molecules, because these molecules serve as the autoinducers involved in "quorum sensing" systems. Other communication mechanisms employ volatile signaling molecules that regulate different bacterial processes. The Arthrobacter agilis strain UMCV2 is a plant growth promoting actinobacterium, which induces plant growth and inhibits phytopathogenic fungi by emitting the dimethylhexadecylamine (DMHDA). However, little is known about the effect of this volatile compound on A. agilis UMCV2 itself, as well as on other bacteria. By exposing A. agilis UMCV2 and bacteria of the genus Bacillus and Pseudomonas to different concentrations of DMHDA, this study showed the dose-dependent effects of DMHDA on A. agilis UMCV2 growth, cellular viability, swarming motility, and expression of marker genes of the flagellar apparatus of bacteria. DMHDA was found to also modulate swarming motility of Bacillus sp. ZAP018 and P. fluorescens UM270, but not that of P. aeruginosa PA01. These data indicate that DMHDA is involved in both intra- and inter-specific bacterial interaction.

The Suitability of Orthogonal Hosts to Study Plant Cell Wall Biosynthesis.

Plant cells are surrounded by an extracellular matrix that consists mainly of polysaccharides. Many molecular components involved in plant cell wall polymer synthesis have been identified, but it remains largely unknown how these molecular players function together to define the length and decoration pattern of a polysaccharide. Synthetic biology can be applied to answer questions beyond individual glycosyltransferases by reconstructing entire biosynthetic machineries required to produce a complete wall polysaccharide. Recently, this approach was successful in establishing the production of heteromannan from several plant species in an orthogonal host-a yeast-illuminating the role of an auxiliary protein in the biosynthetic process. In this review we evaluate to what extent a selection of organisms from three kingdoms of life (Bacteria, Fungi and Animalia) might be suitable for the synthesis of plant cell wall polysaccharides. By identifying their key attributes for glycoengineering as well as analyzing the glycosidic linkages of their native polymers, we present a valuable comparison of their key advantages and limitations for the production of different classes of plant polysaccharides.