The In Vitro Mass-Produced Model Mycorrhizal Fungus, Rhizophagus irregularis, Significantly Increases Yields of the Globally Important Food Security Crop Cassava.

The arbuscular mycorrhizal symbiosis is formed between arbuscular mycorrhizal fungi (AMF) and plant roots. The fungi provide the plant with inorganic phosphate (P). The symbiosis can result in increased plant growth. Although most global food crops naturally form this symbiosis, very few studies have shown that their practical application can lead to large-scale increases in food production. Application of AMF to crops in the tropics is potentially effective for improving yields. However, a main problem of using AMF on a large-scale is producing cheap inoculum in a clean sterile carrier and sufficiently concentrated to cheaply transport. Recently, mass-produced in vitro inoculum of the model mycorrhizal fungus Rhizophagus irregularis became available, potentially making its use viable in tropical agriculture. One of the most globally important food plants in the tropics is cassava. We evaluated the effect of in vitro mass-produced R. irregularis inoculum on the yield of cassava crops at two locations in Colombia. A significant effect of R. irregularis inoculation on yield occurred at both sites. At one site, yield increases were observed irrespective of P fertilization. At the other site, inoculation with AMF and 50% of the normally applied P gave the highest yield. Despite that AMF inoculation resulted in greater food production, economic analyses revealed that AMF inoculation did not give greater return on investment than with conventional cultivation. However, the amount of AMF inoculum used was double the recommended dose and was calculated with European, not Colombian, inoculum prices. R. irregularis can also be manipulated genetically in vitro, leading to improved plant growth. We conclude that application of in vitro R. irregularis is currently a way of increasing cassava yields, that there is a strong potential for it to be economically profitable and that there is enormous potential to improve this efficiency further in the future.

Defining molecular components of symbiotic phosphate uptake in rice

Phosphate (Pi) acquisition of crops via arbuscular mycorrhizal (AM) symbiosis acquires increasing importance due to the limited rock Pi reserves and the demand for environmentally sustainable agriculture. However, the symbiotic Pi uptake machinery has not been characterized in any monocotyledonous plant species. Among these, rice is the primary staple food for more than half of the human population and thus central for future food security. However, the relevance of the AM symbiosis for rice Pi nutrition is presently unclear. Here, we show that 70% of the overall Pi acquired by rice is delivered via the symbiotic route. To better understand this pathway we combined genetic, molecular and physiological approaches to determine the specific functions of the two rice Pi transporters, PT11 and PT13, which are expressed only during AM symbiosis. The PT11 lineage of proteins is present in mono- and dicotyledons whereas PT13, while found across the Poaceae, is absent from dicotyledons. Surprisingly, mutations in either PT11 or PT13 affected fungal colonization and arbuscule formation demonstrating that both genes are essential for AM symbiosis between rice and Glomus intra.rad.ices. Importantly, for symbiotic Pi uptake, only PT11 is necessary and sufficient. We found that mycorrhizal rice, remarkably, received almost all Pi via the symbiotic route. Such dominating mycorrhizal Pi uptake was found in plants grown under controlled conditions as well as in field soils, suggesting that the AM symbiosis is relevant for the Pi nutrition of field grown rice. Development of smaller arbuscules in PT11 mutants suggested that symbiotic Pi signaling is required for fungal nourishment by the plant. However, co-culture of mutant with wild type nurse plants did not restore normal arbuscule size in mutant roots, indicating that other factors than malnutrition accounted for the altered arbuscule phenotype. Surprisingly, the loss of PT13 did not affect symbiotic Pi uptake although it impacted arbuscule morphology, suggesting that PT13 is involved in signaling during arbuscule development. However, induction of PT13 was not only monitored in arbusculated cells but also in inner cortex cells of non-inoculated roots of plants grown under high Pi fertilization conditions. According to preliminary observations, PT13 localized at the tonoplast in arbusculated and non-arbusculated cells, suggesting that it might be involved in transporting Pi into the vacuole, possibly for maintaining cellular Pi homeostasis. The further investigation showed that fungal colonization level was significantly affected in the crown roots of two ptlS mutant alleles, but not in large lateral roots, implying the possible role of PT13 for maintaining Pi homeostasis in the crown roots. - L'acquisition de phosphate (Pi) par les plantes cultivées s'effectue grâce à une symbiose mycorhizienne arbasculaire (AM). L'étude de cette symbiose devient fondamentale puisque d'une part, les réserves en phosphate minéral sont limitées, et, d'autre part, la demande pour une agriculture écologiquement soutenable se renforce. La machinerie d'absorption symbiotique du phosphate n'est cependant pas encore élucidée chez les plantes monocotylédones. Parmi celles-ci, le riz occupe une place primordiale. Aliment de base pour plus de la moitié de la population mondiale, il revêt de ce fait une dimension essentielle en termes de sécurité alimentaire. Pourtant, l'importance de la symbiose AM chez le riz dans le processus d'acquisition du phosphate n'est, encore de nos jours, que peu comprise. Dans cette étude, nous montrons que 70% du phosphate acquis par le riz est mis à disposition de la plante grâce à la symbiose AM. Afin de mieux comprendre ce mécanisme, nous avons employé des approches physiologiques et génétiques nous permettant de déterminer les fonctions spécifiques de deux transporteurs de Pi, PT11 et PT13, présents chez le riz et exprimés uniquement durant la symbiose AM. La famille de gènes à laquelle appartient PT11 est présente chez les monocotylédones ainsi que chez les dicotylédones tandis que PT13, bien que retrouvé au sein des Poaceae, est absent chez les dicotylédones. Etonnamment, des versions mutées de PT11 ou de PT13 affectent la colonisation par le champignon endo-mycorhizien ainsi que la formation d'arbuscules, démontrant l'importance de ces deux gènes dans la symbiose AM entre le riz et Glomus intraradices. Il est à noter que seul PT11 se révèle nécessaire et suffisant pour l'apport de Pi grâce à la symbiose. Nous avons observé que la presque totalité du phosphate dont dispose le riz lors d'une symbiose AM provient du champignon. De telles proportions ont été observées tant chez des plantes cultivées en conditions contrôlées que chez des plantes cultivées dans les champs. Cela suggère l'importance de la symbiose AM dans le processus d'acquisition du Pi chez le riz cultivé à l'extérieur. Le développement d'arbuscules plus petits chez le mutant PT11 tend à montrer qu'une voie signalétique impliquant le Pi symbiotique est nécessaire pour l'entretien du champignon par la plante. Toutefois, une co-culture du mutant avec des plantes sauvages ne permet pas de restaurer des arbuscules de taille normale dans les racines du mutant. Ce résultat indique le rôle de facteurs autres que la malnutrition aboutissant à la formation d'arbuscules altérés. Si la perte de PT13 n'affecte pas l'acquisition de phosphate symbiotique, la morphologie de l'arbuscule est, quant à elle, modifiée. Ceci suggère un rôle de PT13 durant le développement de l'arbuscule. Or, l'induction de PT13 est non seulement détectée dans des cellules contenant des arbuscules mais également dans des cellules du cortex, ceci chez des plantes cultivées sans champignon mais dans des conditions de fortes concentrations en engrais phosphaté. En accord avec des observations précédentes, PT13 est localisé au niveau du tonoplaste des cellules contenant ou non des arbuscules. Ceci suggère que PT13 pourrait être impliqué dans le transport du Pi vers la vacuole, éventuellement pour maintenir une certaine homéostasie du phosphate. Dans cette étude, nous démontrons également que le niveau de colonisation par le champignon est affecté de manière significative dans les racines principales des deux allèles du mutants ptl3, mais pas dans les grosses racines latérales. Cela impliquerait un rôle possible de PT13 dans le maintien de l'homéostasie du phosphate dans les racines principales. RESUME POUR UN LARGE PUBLIC Le phosphate (Pi), l'un des éléments minéraux essentiel au développement des plantes, se trouve généralement en faible quantité dans le sol, limitant ainsi la croissance des plantes. Le rendement de la production agricole dépend dès lors de l'addition d'engrais contenant du phosphate inorganique (Pi), obtenu à partir de ressources minières riches en phosphate. Or, ces ressources devraient être épuisées d'ici la fin du siècle. Les racines des plantes possèdent des transporteurs de phosphate efficaces leur permettant d'acquérir rapidement le Pi présent dans le sol. Comme le Pi s'avère immobile dans le sol, l'absorption rapide par les racines crée des zones pauvres en Pi autour des systèmes racinaires. Pour surmonter cet obstacle, les plantes ont développé une symbiose avec des champignons endomycorhiziens, la symbiose mycorhizienne arbusculaire (AM). Cette association leur donne accès à d'autres ressources en phosphate puisque le mycélium de ces champignons se développe sur une surface 100 fois supérieure à celle des racines. Cela augmente considérablement la surface de nutrition, dépassant ainsi la zone appauvrie en Pi. Le phosphate, transporté grâce au champignon jusqu'à l'intérieur des racines, est fourni à la plante par le biais de structures établies à l'intérieur des cellules végétales, appelées arbuscules. De leur côté, les plantes possèdent des transporteurs spécifiques afin de recevoir le Pi fourni par les champignons. A l'heure actuelle, la machinerie nécessaire à cette absorption a été uniquement décrite chez des plantes dicotylédones. Or, comprendre l'apport de phosphate par les champignons mycorhiziens s'avère particulièrement pertinent dans le cas des espèces monocotylédones cultivées telles que les céréales. Ces dernières constituent en effet la majeure partie de l'alimentation humaine. Parmi les céréales, le riz demeure l'aliment de base de la population mondiale, d'où son importance en terme de sécurité alimentaire. Durant mon travail de thèse, j'ai identifié et caractérisé le transporteur du riz impliqué dans l'apport de phosphate par ce type de symbiose AM. J'ai également démontré que le riz, lorsqu'il vit en symbiose, bénéficie de la presque totalité du Pi transporté par le champignon. Environ 40% de la production globale de riz est cultivée dans des conditions permettant la symbiose avec des mycorhizes arbusculaires. Les variétés de riz adaptées à ces conditions aérobiques deviennent des alternatives favorables aux cultivars actuels nécessitant une forte irrigation. Elles se révèlent en effet plus tolérantes aux pénuries d'eau et permettent l'utilisation de pratiques agricoles moins intensives. Les données présentées dans cette étude enrichissent nos connaissances concernant l'absorption du phosphate chez le riz grâce à la symbiose AM. Ces connaissances peuvent s'avérer décisives pour le développement de cultivars du riz plus adaptés à une agriculture écologiquement soutenable.

The role of community and population ecology in applying mycorrhizal fungi for improved food security.

The global human population is expected to reach ∼9 billion by 2050. Feeding this many people represents a major challenge requiring global crop yield increases of up to 100%. Microbial symbionts of plants such as arbuscular mycorrhizal fungi (AMF) represent a huge, but unrealized resource for improving yields of globally important crops, especially in the tropics. We argue that the application of AMF in agriculture is too simplistic and ignores basic ecological principals. To achieve this challenge, a community and population ecology approach can contribute greatly. First, ecologists could significantly improve our understanding of the determinants of the survival of introduced AMF, the role of adaptability and intraspecific diversity of AMF and whether inoculation has a direct or indirect effect on plant production. Second, we call for extensive metagenomics as well as population genomics studies that are crucial to assess the environmental impact that introduction of non-local AMF may have on native AMF communities and populations. Finally, we plead for an ecologically sound use of AMF in efforts to increase food security at a global scale in a sustainable manner.

Food habits and sport activity during adolescence: differences between athletic and non-athletic teenagers in Switzerland.

OBJECTIVE: To describe food habits and dietary intakes of athletic and non-athletic adolescents in Switzerland. SETTING: College, high schools and professional centers in the Swiss canton of Vaud. METHOD: A total of 3,540 subjects aged 9-19 y answered a self-reported anonymous questionnaire to assess lifestyles, physical plus sports activity and food habits. Within this sample, a subgroup of 246 subjects aged 11-15 also participated in an in-depth ancillary study including a 3 day dietary record completed by an interview with a dietician. RESULTS: More boys than girls reported engaging in regular sports activities (P<0.001). Adolescent food habits are quite traditional: up to 15 y, most of the respondents have a breakfast and eat at least two hot meals a day, the percentages decreasing thereafter. Snacking is widespread among adolescents (60-80% in the morning, 80-90% in the afternoon). Food habits among athletic adolescents are healthier and also are perceived as such in a higher proportion. Among athletic adolescents, consumption frequency is higher for dairy products and ready to eat (RTE) cereals, for fruit, fruit juices and salad (P<0.05 at least). Thus the athletic adolescent's food brings more micronutrients than the diet of their non-athletic counterparts. Within the subgroup (ancillary study), mean energy intake corresponds to requirements for age/gender group. CONCLUSIONS: Athletic adolescents display healthier food habits than non-athletic adolescents: this result supports the idea that healthy behavior tends to cluster and suggests that prevention programs among this age group should target simultaneously both sports activity and food habits.

Food availability affects the maternal transfer of androgens and antibodies into eggs of a colonial seabird.

Mothers can improve the quality of their offspring by increasing the level of certain components in their eggs. To examine whether or not mothers increase deposition of such components in eggs as a function of food availability, we food-supplemented black-legged kittiwake females (Rissa tridactyla) before and during egg laying and compared deposition of androgens and antibodies into eggs of first and experimentally induced replacement clutches. Food-supplemented females transferred lower amounts of androgens and antibodies into eggs of induced replacement clutches than did non-food-supplemented mothers, whereas first clutches presented no differences between treatments. Our results suggest that when females are in lower condition, they transfer more androgens and antibodies into eggs to facilitate chick development despite potential long-term costs for juveniles. Females in prime condition may avoid these potential long-term costs because they can provide their chicks with more and higher quality resources.

Effects of the naturally occurring food mycotoxin ochratoxin A on brain cells in culture.

The potential of ochratoxin A (OTA) to damage brain cells was studied by using a three-dimensional cell culture system as model for the developing brain. Aggregating cell cultures of foetal rat telencephalon were tested either during an early developmental period, or during a phase of advanced maturation, over a wide range of OTA concentrations (0.4 nM to 50 microM). By monitoring changes in activities of cell type-specific enzymes (ChAt and GAD, for cholinergic and GABAergic neurones, respectively, GS for astrocytes and CNP for oligodendrocytes), the concentration-dependent toxicity and neurodevelopmental effects of OTA were determined. OTA proved to be highly toxic, since a 10-day treatment at 50 nM caused a general cytotoxicity in both mature and immature cultures. At 10 nM of OTA, cell type-specific effects were observed: in immature cultures, a loss in neuronal and oligodendroglial enzyme activities, and an increase in the activity of the astroglial marker glutamine synthetase were found, Furthermore, at 2 and 10 nM of OTA, a clustering of microglial cells was observed. In mature cultures, OTA was somewhat less potent, but caused a similar pattern of toxic effects. A 24 h-treatment with OTA resulted in a concentration-dependent decrease in protein synthesis, with IC50 values of 25 nM and 33 nM for immature and mature cultures respectively. Acute (24 h) treatment at high OTA concentrations (10 to 50 microM) caused a significant increase in reactive oxygen species formation, as measured by the intracellular oxidation of 2',7'-dichlorofluorescin. These results suggest that OTA has the potential to be a potent toxicant to brain cells, and that its effects at nanomolar concentrations are primarily due to the inhibition of protein synthesis, whereas ROS seem not to be involved in the toxicity mediated by a chronic exposure to OTA at such low concentrations.

Predicting positive food challenges in children sensitised to peanuts/tree nuts.

BACKGROUND: Children with atopic diseases in early life are frequently found with positive IgE tests to peanuts/tree nuts without a history of previous ingestion. We aimed to identify risk factors for reactions to nuts at first introduction. METHODS: A retrospective case-note and database analysis was performed. Recruitment criteria were: patients aged 3-16 yr who had a standardized food challenge to peanut and/or tree nuts due to sensitisation to the peanut/tree nut (positive spIgE or SPT) without previous consumption. A detailed assessment was performed of factors relating to food challenge outcome with univariate and multivariate logistic regression analysis. RESULTS: There were 98 food challenges (47 peanut, 51 tree nut) with 29 positive, 67 negative and 2 inconclusive outcomes. A positive maternal history of allergy and a specific IgE >5 kU/l were strongly associated with a significantly increased risk of a positive food challenge (OR 3.73; 95% CI 1.31-10.59; p = 0.013 and OR 3.35; 95% CI 1.23-9.11; p = 0.007, respectively). Adjusting for age, a three year-old with these criteria has a 67% probability of a positive challenge. There was no significant association between types of peanut/tree nut, other food allergies, atopic conditions or severity of previous food reactions and positive challenges. CONCLUSIONS: We have demonstrated an association between the presence of maternal atopic history and a specific IgE >5 kU/l, with a significant increase in the likelihood of a positive food challenge. Although requiring further prospective validation these easily identifiable components should be considered when deciding the need for a challenge.

Ecologic correlations of selected food groups with disease incidence and mortality in Switzerland.

Background: There is little information regarding the impact of diet on disease incidence and mortality in Switzerland. We assessed ecologic correlations between food availability and disease.Methods: In this ecologic study for the period 1970-2009, food availability was measured using the food balance sheets of the Food and Agriculture Organization of the United Nations. Standardized mortality rates (SMRs) were obtained from the Swiss Federal Office of Statistics. Cancer incidence data were obtained from the World Health Organization Health For All database and the Vaud Cancer Registry. Associations between food availability and mortality/incidence were assessed at lags 0, 5, 10, and 15 years by multivariate regression adjusted for total caloric intake.Results: Alcoholic beverages and fruit availability were positively associated, and fish availability was inversely associated, with SMRs for cardiovascular diseases. Animal products, meat, and animal fats were positively associated with the SMR for ischemic heart disease only. For cancer, the results of analysis using SMRs and incidence rates were contradictory. Alcoholic beverages and fruits were positively associated with SMRs for all cancer but inversely associated with all-cancer incidence rates. Similar findings were obtained for all other foods except vegetables, which were weakly inversely associated with SMRs and incidence rates. Use of a 15-year lag reversed the associations with animal and vegetal products, weakened the association with alcohol and fruits, and strengthened the association with fish.Conclusions: Ecologic associations between food availability and disease vary considerably on the basis of whether mortality or incidence rates are used in the analysis. Great care is thus necessary when interpreting our results.

Peroxisomal polyhydroxyalkanoate biosynthesis is a promising strategy for bioplastic production in high biomass crops.

Polyhydroxyalkanoates (PHAs) are bacterial carbon storage polymers with diverse plastic-like properties. PHA biosynthesis in transgenic plants is being developed as a way to reduce the cost and increase the sustainability of industrial PHA production. The homopolymer polyhydroxybutyrate (PHB) is the simplest form of these biodegradable polyesters. Plant peroxisomes contain the substrate molecules and necessary reducing power for PHB biosynthesis, but peroxisomal PHB production has not been explored in whole soil-grown transgenic plants to date. We generated transgenic sugarcane (Saccharum sp.) with the three-enzyme Ralstonia eutropha PHA biosynthetic pathway targeted to peroxisomes. We also introduced the pathway into Arabidopsis thaliana, as a model system for studying and manipulating peroxisomal PHB production. PHB, at levels up to 1.6%-1.8% dry weight, accumulated in sugarcane leaves and A. thaliana seedlings, respectively. In sugarcane, PHB accumulated throughout most leaf cell types in both peroxisomes and vacuoles. A small percentage of total polymer was also identified as the copolymer poly (3-hydroxybutyrate-co-3-hydroxyvalerate) in both plant species. No obvious deleterious effect was observed on plant growth because of peroxisomal PHA biosynthesis at these levels. This study highlights how using peroxisomal metabolism for PHA biosynthesis could significantly contribute to reaching commercial production levels of PHAs in crop plants.

Indirect costs of parasitism are shaped by variation in the type of immune challenge and food availability

Parasites can inflict indirect fitness costs to their hosts by eliciting costly immune responses. These costs depend on the type and amount of immunostimulants presented to the host immune system but also on the amount of resources available to fuel host immune responses. Here, we investigated how the relative costs of two different types of immune challenge are modulated by variation in food availability. We injected nestling tawny owls (Strix aluco) with either 10 mu g of phytohaemagglutinin (PHA) or 20 mu g of lipopolysaccharide (LPS), and subsequently raised them under two different food regimes (food-restricted vs. ad libitum). After controlling for food consumption, we found that LPS-injected nestlings lost more body mass than PHA-injected ones only when food-restricted. We also found that body mass gain of owlets fed ad libitum decreased with the intensity of the skin swelling response against LPS, but not PHA. These experimental and correlative results suggest that nestling tawny owls suffered greater immune costs when treated with LPS than PHA, and that variation in the costs of two different types of immune challenge can be exacerbated under conditions of low food availability. Our study highlights the importance of taking into consideration the interplay between host immunity and nutrition in the study of indirect costs of parasitism.

Nutrition transition in a middle-income country: 22-year trends in the Seychelles.

BACKGROUND/OBJECTIVES: There is little objective information regarding nutrition transition in African countries. We assessed trends in nutrition patterns in the Seychelles between 1989 and 2011. SUBJECTS/METHODS: Population-based samples were obtained in 1989, 1994 and 2011 and participants aged 25-44 are considered in this study (n=493, 599 and 471, respectively). Similar, although not identical, food frequency questionnaires (FFQs) were used in each survey and the variables were collapsed into homogenous categories for the purpose of this study. RESULTS: Between 1989 and 2011, consumption frequency of fish (5+/week) decreased from 93 to 74%, whereas the following increased: meat (5+/week) 25 to 51%, fruits (1+/week) 48 to 94%, salty snacks (1+/week) 22 to 64% and sweet snacks (1+/week) 38 to 67% (P<0.001 for all). Consumption frequency decreased for home-brewed alcoholic drinks (1+/week) 16 to 1%, but increased for wine (1+/week) 5 to 33% (both P<0.001). Between 2004 and 2011, consumption frequency decreased for rice (2/day) 62 to 57% and tea (1+/day) 72 to 68%, increased for poultry (1+/week) 86 to 96% (all P<0.01), and did not change for vegetables (70.3 to 69.8%, P=0.65). CONCLUSIONS: Seychelles is experiencing nutrition transition characterized by a decreased consumption frequency of traditional staple foods (fish, polished rice), beverages (tea) and of inexpensive home brews, and increased consumption frequency of meat, poultry and snacks. Food patterns also became more varied along with a broader availability of products in the 22-year interval. The health impact of these changes should be further studied.

Les préférences alimentaires sont-elles influencées par l'index de masse corporelle, l'âge, le sexe ou le tabac [Are food preferences affected by body mass index, age, sex or tobacco?].

In recent decades the percentage of energy derived from dietary fat has increased. The aim of this study was to explore the relationship between food taste preferences, BMI, age, gender and smoking habits. A computerized questionnaire using a hedonic scale (range 0 to 8) to quantify the liking for sweet and savoury, lean and fat foods, was filled by 233 adults: 171 normal weight (131 women, 40 men) and 62 overweight subjects (BMI > 25 kg/m2 42 women, 20 men). The majority of the subjects had a general preference for savoury lean food irrespective of their BMI or gender. Similarly, preference for sweet lean food was not influenced by the magnitude of the BMI. In contrast, overweight subjects had a preference for sweet fat food (p = 0.05) as well as for savoury fat food (p < 0.05). At any age or BMI, men preferred sweet fat food (p < 0.01). This was not the case for women. Overweight men over forty preferred savoury fat food, in contrast to overweight women of the same age (p < 0.01). The same difference existed between normal weight smokers and non-smokers. This study demonstrates that fat food preference plays a potential role in the development of obesity.