Folate Biofortification of Potato by Tuber-Specific Expression of Four Folate Biosynthesis Genes.

Insufficient dietary intake of micronutrients, known as "hidden hunger", is a devastating global burden, affecting two billion people. Deficiency of folates (vitamin B9), which are known to play a central role in C1 metabolism, causes birth defects in at least a quarter million people annually. Biofortification to enhance the level of naturally occurring folates in crop plants, proves to be an efficient and cost-effective tool in fighting folate deficiency. Previously, introduction of folate biosynthesis genes GTPCHI and ADCS, proven to be a successful biofortification strategy in rice and tomato, turned out to be insufficient to adequately increase folate levels in potato tubers. Here, we provide a proof of concept that additional introduction of HPPK/DHPS and/or FPGS, downstream genes in mitochondrial folate biosynthesis, enables augmentation of folates to satisfactory levels (12-fold) and ensures folate stability upon long-term storage of tubers. In conclusion, this engineering strategy can serve as a model in the creation of folate-accumulating potato cultivars, readily applicable in potato-consuming populations suffering from folate deficiency.

Methods matter: a meta-regression on the determinants of willingness-to-pay studies on biofortified foods.

Following the growing evidence on biofortification as a cost-effective micronutrient strategy, various researchers have elicited consumers' willingness to pay (WTP) for biofortified crops in an effort to justify and determine their adoption. This review presents a meta-analysis of WTP studies on biofortified foods, either developed through conventional breeding or using genetic modification technology. On the basis of 122 estimates from 23 studies (9507 respondents), consumers are generally willing to pay 21.3% more for biofortified crops. Because WTP estimates are often determined through different valuation methods and procedures, a meta-regression was carried out to examine the role of potential determinants. Aside from contextual factors, such as type of food crop, target nutrient, and region (but not breeding technique), various methodological factors significantly influence premiums, including the type of respondent, nature of the study, study environment, participation fee, and provided information. The findings allow researchers to better anticipate potential methodological biases when examining WTP for (biofortified) foods, while it gives policy makers a broad understanding of the potential demand for different biofortified crops in various settings.

The socioeconomics of genetically modified biofortified crops: a systematic review and meta-analysis.

Building upon the growing interest and research on genetically modified (GM) biofortification, its socioeconomic potential has been increasingly examined. We conducted two systematic reviews and meta-analyses to provide comprehensive evidence of consumers' willingness to pay (11 economic valuation studies, 64 estimates) and cost-effectiveness/benefits (five economic evaluation studies, 30 estimates). Worldwide, consumers were willing to pay 23.9% more for GM biofortified food crops. Aside from crop and design-related differences, information provision was deemed crucial. Positive information (nutrition and GM benefits) is associated with the highest consumer willingness to pay, compared with negative, objective, and conflicting GM information, especially when negative information was mentioned last. This health intervention would reduce the aggregated micronutrient deficiency burden in Asia (15.6 million disability-adjusted life years (DALYs)) by 12.5-51.4%, at a low cost of USD 7.9-27.8 per DALY in a pessimistic and optimistic scenario, respectively. Given that GM biofortified crops could tackle hidden hunger in a cost-effective and well-accepted way, its implementation is worth pursuing. A case study on folate biofortification further elaborates on the importance of socioeconomic research and the determinants of their market potential.

Metabolic engineering of micronutrients in crop plants.

Micronutrient deficiency is a widespread phenomenon, most prevalent in developing countries. Being causally linked to the occurrence of a range of diseases, it affects billions of people worldwide. Enhancing the content of micronutrients in crop products through biotechnology is a promising technique to fight micronutrient malnutrition worldwide. Micronutrient fortification of food products has been implemented in a number of Western countries, but remains inaccessible for poor rural populations in a major part of the developing world. Moreover, evidence of the negative impacts of this practice on human health, at least for some vitamins, is accumulating. Biofortification of crop plants-the enhancement of vitamins and minerals through plant biotechnology-is a promising alternative or complement in the battle against micronutrient deficiencies. Owing to a growing knowledge about vitamin metabolism, as well as mineral uptake and reallocation in plants, it is today possible to enhance micronutrient levels in crop plants, offering a sustainable solution to populations with a suboptimal micronutrient intake.

Degradation and interconversion of plant pteridines during sample preparation and ultra-high performance liquid chromatography-tandem mass spectrometry.

The degradation and interconversion of a selected set of pterins (dihydroneopterin, hydroxymethyldihydropterin, dihydroxanthopterin, neopterin, hydroxymethylpterin, xanthopterin, 6-formylpterin, 6-carboxypterin and pterin), spiked to charcoal-treated potato and Arabidopsis thaliana matrix was investigated, together with their relative recovery in potato and A. thaliana. As a result, a matrix-specific procedure for the ultra-high performance liquid chromatography-tandem mass spectrometry based determination of 6 aromatic pterins (neopterin, hydroxymethylpterin, xanthopterin, 6-formylpterin, 6-carboxypterin and pterin) is proposed: 1.5ml of an N2-flushed, alkaline (pH=10) extraction solvent is added to 200mg of plant sample. After boiling and homogenization, the samples are incubated: Arabidopsis samples for 30min at room temperature, while shaking, and potato samples for 2h at 37°C (applying a dienzyme treatment with α-amylase and protease). After a final boiling step, the samples are ultrafiltrated and resulting extracts are analyzed by UHPLC-MS/MS.

Determination of five folate monoglutamates in rodent diets.

A method for the quantitative determination of folates in rodent diets is very important for correct interpretation of folate intake during feeding trials, given the possible discrepancy between the actual folate concentration in the diet and that mentioned on the product sheet. Liquid chromatography tandem-mass spectrometry is the method of choice to differentiate and quantify the individual folate species present. This discrepancy may be accounted for by, e.g., inaccurate folic acid supplementation and/or the presence of endogenous reduced and substituted folates. We developed a method, validated based on FDA guidelines, that allows the measurement of added and endogenous folates by quantitative determination of 5 folate monoglutamates with linear ranges from 8 µg to 2 mg/kg feed. This information, combined with feed intake data, allows insight into the actual folate intake in animal feeding studies. The relevance of this method was illustrated by the analysis of several feed samples of varying composition, by the investigation of the effect of casein incorporation, and by evaluating the variability of the folate content between pellets and production batches.

Improving folate (vitamin B9) stability in biofortified rice through metabolic engineering.

Biofortification of staple crops could help to alleviate micronutrient deficiencies in humans. We show that folates in stored rice grains are unstable, which reduces the potential benefits of folate biofortification. We obtain folate concentrations that are up to 150 fold higher than those of wild-type rice by complexing folate to folate-binding proteins to improve folate stability, thereby enabling long-term storage of biofortified high-folate rice grains.

Folates from metabolically engineered rice: a long-term study in rats.

SCOPE: The biological impact of folates from folate rice, a metabolically engineered (biofortified) rice line, rich in folates, was investigated. Its consumption may be helpful to fight folate deficiency. Our objective was to investigate the potential of folate rice to supply the organism with folates and evaluate its biological effectiveness using a rat model. METHODS AND RESULTS: Five groups of 12 Wistar rats were monitored during a 7/12-wk depletion/repletion trial. Animals receiving folate-free diet (0 µg/rat/day) and those additionally receiving wild-type rice (on average 0.11 µg/rat/day) suffered from decreased hematocrit and lower folate concentrations in both plasma and RBCs. This resulted in serious morbidity and even lethality during the trial. In contrast, all animals receiving a daily supplement of folate rice or folic acid fortified rice (on average 3.00 µg/rat/day and 3.12 µg/rat/day, respectively) and those receiving a positive control diet (11.4 to 25.0 µg/rat/day), survived. In these groups, the hematocrit normalized, plasma and RBC folate concentrations increased and pronounced hyperhomocysteinemia was countered. CONCLUSION: Using an animal model, we demonstrated that biofortified folate rice is a valuable source of dietary folate, as evidenced by folate determination in plasma and RBCs, the alleviation of anemia and counteraction of pronounced hyperhomocysteinemia.

Wounding stress causes rapid increase in concentration of the naturally occurring 2',3'-isomers of cyclic guanosine- and cyclic adenosine monophosphate (cGMP and cAMP) in plant tissues.

3',5'-Cyclic guanosine monophosphate (cGMP) and 3',5'-cyclic adenosine monophosphate (cAMP) are well reported second messenger molecules involved in cellular signal transduction, in physiological functions such as neurotransmission in animals and in the modulation of cell growth and differentiation. In plants, 3',5'-cyclic nucleotides have been implicated in the regulation of ion homeostasis, hormone and stress responses. The behavior of the 2',3'-cyclic nucleotide variants is also known in animal tissue but no quantitative information is available about 2',3'-cAMP and 2',3'-cGMP in plant material. A recently developed HILIC-SPE/LC-MS/MS method for the analysis of cyclic nucleotides in blood and animal tissue was therefore adapted to measure 2',3'-cAMP and 2',3'-cGMP concentrations in plant material. Cyclic nucleotide concentrations were measured in Arabidopsis thaliana (Col-0) leaves before and after the application of wounding stress. A significant (∼5-fold) up-regulation of 2',3'-cAMP and 2',3'-cGMP was measured in Arabidopsis leaves compared to the control samples. The results indicate a thus far unreported strong correlation between plant stress and both 2',3'-cAMP and 2',3'-cGMP levels in plant material, and may open new avenues towards understanding the role of cyclic nucleotides in plants.

Present and future of folate biofortification of crop plants.

Improving nutritional health is one of the major socio-economic challenges of the 21st century, especially with the continuously growing and ageing world population. Folate deficiency is an important and underestimated problem of micronutrient malnutrition affecting billions of people worldwide. More and more countries are adapting policies to fight folate deficiency, mostly by fortifying foods with folic acid. However, there is growing concern about this practice, calling for alternative or complementary strategies. In addition, fortification programmes are often inaccessible to remote and poor populations where folate deficiency is most prevalent. Enhancing folate content in staple crops by metabolic engineering is a promising, cost-effective strategy to eradicate folate malnutrition worldwide. Over the last decade, major progress has been made in this field. Nevertheless, engineering strategies have thus far been implemented on a handful of plant species only and need to be transferred to highly consumed staple crops to maximally reach target populations. Moreover, successful engineering strategies appear to be species-dependent, hence the need to adapt them in order to biofortify different staple crops with folate.

Enhancing pterin and para-aminobenzoate content is not sufficient to successfully biofortify potato tubers and Arabidopsis thaliana plants with folate.

Folates are important cofactors in one-carbon metabolism in all living organisms. Since only plants and micro- organisms are capable of biosynthesizing folates, humans depend entirely on their diet as a folate source. Given the low folate content of several staple crop products, folate deficiency affects regions all over the world. Folate biofortification of staple crops through enhancement of pterin and para-aminobenzoate levels, precursors of the folate biosynthesis pathway, was reported to be successful in tomato and rice. This study shows that the same strategy is not sufficient to enhance folate content in potato tubers and Arabidopsis thaliana plants and concludes that other steps in folate biosynthesis and/or metabolism need to be engineered to result in substantial folate accumulation. The findings provide a plausible explanation why, more than half a decade after the proof of concept in rice and tomato, successful folate biofortification of other food crops through enhancement of para-aminobenzoate and pterin content has not been reported thus far. A better understanding of the folate pathway is required in order to determine an engineering strategy that can be generalized to most staple crops.

Rice folate enhancement through metabolic engineering has an impact on rice seed metabolism, but does not affect the expression of the endogenous folate biosynthesis genes.

Folates are key-players in one-carbon metabolism in all organisms. However, only micro-organisms and plants are able to synthesize folates de novo and humans rely entirely on their diet as a sole folate source. As a consequence, folate deficiency is a global problem. Although different strategies are currently implemented to fight folate deficiency, up until now, all of them have their own drawbacks. As an alternative and complementary means to those classical strategies, folate biofortification of rice by metabolic engineering was successfully achieved a couple of years ago. To gain more insight into folate biosynthesis regulation and the effect of folate enhancement on general rice seed metabolism, a transcriptomic study was conducted in developing transgenic rice seeds, overexpressing 2 genes of the folate biosynthetic pathway. Upon folate enhancement, the expression of 235 genes was significantly altered. Here, we show that rice folate biofortification has an important effect on folate dependent, seed developmental and plant stress response/defense processes, but does not affect the expression of the endogenous folate biosynthesis genes.

Ex-ante evaluation of biotechnology innovations: the case of folate biofortified rice in China.

In order to valorize novel biotechnology innovations, there is a need to evaluate ex-ante their market potential. A case in point is biofortification, i.e. the enhancement of the micronutrient content of staple crops through conventional or genetic breeding techniques. In a recent article in Nature Biotechnology, for example, De Steur et al. (2010) demonstrated the large potential consumer health benefits of folate biofortified rice as a means to reduce folate deficiency and Neural-Tube Defects. By focusing on a Chinese high-risk region of Neural-Tube Defects, the current study defines the potential cost-effectiveness of this genetically modified crop where the need to improve folate intake levels is highest. Building on the Disability-Adjusted Life Years (DALY) approach, both the potential health impacts and costs of its implementation are measured and benchmarked against similar innovations. The results show that this transgenic crop could be a highly cost-effective product innovation (US$ 120.34 - US$ 40.1 per DALY saved) to alleviate the large health burden of folate deficiency and reduce the prevalence of neural-tube birth defects. When compared with other biofortified crops and target regions, folate biofortified rice in China has a relatively high health impact and moderate cost-effectiveness. This research further supports the need for, and importance of ex-ante evaluation studies in order to adequately market and, thus, valorize biotechnology innovations. Although the cost-effectiveness analysis enables to illustrate the market potential of innovative agricultural biotechnology research, further research is required to address policy issues on transgenic biofortification, such as biosafety regulatory requirements.

Potential impact and cost-effectiveness of multi-biofortified rice in China.

Biofortification, that is, improving the micronutrient content of staple foods through crop breeding, could be a pro-poor, pro-rural, agriculture-based intervention to reduce the health burden of micronutrient malnutrition. While the potential cost-effectiveness of crops biofortified with single micronutrients was shown in previous research, poor people often suffer from multiple micronutrient deficiencies, which should be accounted for in biofortification initiatives. This study is the first to estimate the potential health benefits and cost-effectiveness of multi-biofortification. Rice with enhanced provitamin A, zinc, iron and folate concentrations is used as a concrete example. The research is conducted for China, the largest rice producer in the world, where micronutrient malnutrition remains a major public health problem. Using the DALY (disability-adjusted life year) framework, the current annual health burden of the four micronutrient deficiencies in China is estimated at 10.6 million DALYs. Introducing multi-biofortified rice could lower this burden by up to 46%. Given the large positive health impact and low recurrent costs of multi-biofortification, this intervention could be very cost effective: under optimistic assumptions, the cost per DALY saved would be around US$ 2; it would stay below US$ 10 even under pessimistic assumptions.

Folate fortification of rice by metabolic engineering.

Rice, the world's major staple crop, is a poor source of essential micronutrients, including folates (vitamin B9). We report folate biofortification of rice seeds achieved by overexpressing two Arabidopsis thaliana genes of the pterin and para-aminobenzoate branches of the folate biosynthetic pathway from a single locus. We obtained a maximal enhancement as high as 100 times above wild type, with 100 g of polished raw grains containing up to four times the adult daily folate requirement.