RESUMO
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.
Assuntos
Ácido Fólico/química , Ácido Fólico/genética , Melhoramento Genético/métodos , Engenharia Metabólica/métodos , Oryza/química , Oryza/genética , Suplementos Nutricionais , Estabilidade de Medicamentos , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas/química , Plantas Geneticamente Modificadas/genéticaRESUMO
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.
Assuntos
Arabidopsis/genética , Ácido Fólico/metabolismo , GTP Cicloidrolase/genética , Regulação da Expressão Gênica de Plantas , Proteínas de Plantas/genética , Solanum tuberosum/genética , Transaminases/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , DNA Complementar/genética , DNA Complementar/metabolismo , GTP Cicloidrolase/metabolismo , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/metabolismo , Pterinas/metabolismo , Solanum tuberosum/metabolismo , Transaminases/metabolismo , para-Aminobenzoatos/metabolismoRESUMO
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.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/enzimologia , Ácido Fólico/metabolismo , Regulação Enzimológica da Expressão Gênica , Oryza/metabolismo , Sementes/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , DNA Complementar/genética , GTP Cicloidrolase/genética , GTP Cicloidrolase/metabolismo , Expressão Gênica , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Engenharia Metabólica , Análise de Sequência com Séries de Oligonucleotídeos , Oryza/genética , Oryza/crescimento & desenvolvimento , Plantas Geneticamente Modificadas , RNA de Plantas/genética , Reação em Cadeia da Polimerase em Tempo Real , Sementes/genética , Sementes/crescimento & desenvolvimento , Transaminases/genética , Transaminases/metabolismoAssuntos
Ácido Fólico/metabolismo , Alimentos Fortificados , Saúde , Oryza/genética , Disponibilidade Biológica , China , Suplementos Nutricionais , Deficiência de Ácido Fólico/patologia , Defeitos do Tubo Neural/patologia , Plantas Geneticamente Modificadas , Anos de Vida Ajustados por Qualidade de Vida , População RuralRESUMO
Folate deficiency is a global health problem affecting many people in the developing and developed world. Current interventions (industrial food fortification and supplementation by folic acid pills) are effective if they can be used but might not be possible in less developed countries. Recent advances demonstrate that folate biofortification of food crops is now a feasible complementary strategy to fight folate deficiency worldwide. The genes and enzymes of folate synthesis are sufficiently understood to enable metabolic engineering of the pathway, and results from pilot engineering studies in plants (and bacteria) are encouraging. Here, we review the current status of investigations in the field of folate enhancement on the eve of a new era in food fortification.
Assuntos
Ácido Fólico/biossíntese , Plantas Comestíveis/genética , Plantas Comestíveis/metabolismo , Plantas Geneticamente Modificadas , Carbono-Nitrogênio Ligases/genética , Carbono-Nitrogênio Ligases/metabolismo , GTP Cicloidrolase/genética , GTP Cicloidrolase/metabolismo , Modelos Biológicos , Plantas Comestíveis/enzimologia , TransaminasesRESUMO
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.