One out of three humans suffer from micronutrient deficiencies called “hidden hunger”. Underprivileged people, including preschool children and women, suffer most from deficiency diseases and other health-related issues. Rice (Oryza sativa), a staple food, is their source of nutrients, contributing up to 70% of daily calories for more than half of the world’s population. Solving “hidden hunger” through rice biofortification would be a sustainable approach for those people who mainly consume rice and have limited access to diversified food. White milled rice grains lose essential nutrients through polishing. Therefore, seed-specific higher accumulation of essential nutrients is a necessity. Through the method of biofortification (via genetic engineering/molecular breeding), significant increases in iron and zinc with other essential minerals and provitamin-A (β-carotene) was achieved in rice grain. Many indica and japonica rice cultivars have been biofortified worldwide, being popularly known as ‘high iron rice’, ‘low phytate rice’, ‘high zinc rice’, and ‘high carotenoid rice’ (golden rice) varieties. Market availability of such varieties could reduce “hidden hunger”, and a large population of the world could be cured from iron deficiency anemia (IDA), zinc deficiency, and vitamin-A deficiency (VAD). In this review, different approaches of rice biofortification with their outcomes have been elaborated and discussed. Future strategies of nutrition improvement using genome editing (CRISPR/Cas9) and the need of policy support have been highlighted.

https://www.mdpi.com/2073-4395/9/12/803/pdf

Rice Biofortification: High Iron, Zinc, and Vitamin-A to Fight against “Hidden Hunger”

Zinc in plants: Integrating homeostasis and biofortification

Food with higher nutritional value is always desired for human health. Rice is the prime staple food in more than thirty developing countries, providing at least 20% of dietary protein, 3% of dietary fat and other essential nutrients. Several factors influence the nutrient content of rice which includes agricultural practices, post-harvest processing, cultivar type as well as manipulations followed by selection through breeding and genetic means. In addition to mutation breeding, genetic engineering approach also contributed significantly for the generation of nutrition added varieties of rice in the last decade or so. In the present review, we summarize the research update on improving the nutritional characteristics of rice by using genetic engineering and mutation breeding approach. We also compare the conventional breeding techniques of rice with modern molecular breeding techniques toward the generation of nutritionally improved rice variety as compared to other cereals in areas of micronutrients and availability of essential nutrients such as folate and iron. In addition to biofortification, our focus will be on the efforts to generate low phytate in seeds, increase in essential fatty acids or addition of vitamins (as in golden rice) all leading to the achievements in rice nutrition science. The superiority of biotechnology over conventional breeding being already established, it is essential to ascertain that there are no serious negative agronomic consequences for consumers with any difference in grain size or color or texture, when a nutritionally improved variety of rice is generated through genetic engineering technology.

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Genetic Manipulation for Improved Nutritional Quality in Rice.

Functional foods are natural products of plants that have health benefits beyond necessary nutrition. Functional foods are abundant in fruits, vegetables, spices, beverages and some are found in cereals, millets, pulses and oilseeds. Efforts to identify functional foods in our diet and their beneficial aspects are limited to few crops. Advances in sequencing and availability of different omics technologies have given opportunity to utilize these tools to enhance the functional components of the foods, thus ensuring the nutritional security. Integrated omics approaches including genomics, transcriptomics, proteomics, metabolomics coupled with artificial intelligence and machine learning approaches can be used to improve the crops. This review provides insights into omics studies that are carried out to find the active components and crop improvement by enhancing the functional compounds in different plants including cereals, millets, pulses, oilseeds, fruits, vegetables, spices, beverages and medicinal plants. There is a need to characterize functional foods that are being used in traditional medicines, as well as utilization of this knowledge to improve the staple foods in order to tackle malnutrition and hunger more effectively.

Omics Technologies to Enhance Plant Based Functional Foods: An Overview.

Phytic acid accumulation in plants: Biosynthesis pathway regulation and role in human diet.

RNAi-Mediated Silencing of ITPK Gene Reduces Phytic Acid Content, Alters Transcripts of Phytic Acid Biosynthetic Genes, and Modulates Mineral Distribution in Rice Seeds

Phytic acid is the major source of phosphorus and other mineral bound compounds in many plant tissues especially seeds and bran of cereals. During germination, phytase enzyme degrades phytic acid and bound phosphate and minerals are released. The monogastric animal cannot digest phytate due to lack of the phytase enzyme. Considering that, we have generated low phytate rice by over expressing appA gene cloned from E. coli under the aleurone-specific promoter of maize zein gene. Molecular analysis confirmed the stable integration of transgene and plants were grown up to T3 generation. The T3 seeds showed around 45% decrease in seed phytate content with a fourfold increase of inorganic phosphorus (Pi) level. The enhanced iron and zinc was twofold and threefold respectively in polished seeds of transgenic plants. There was no change in germination behaviour and other morphological traits in transgenic seeds. Thus, this result provides evidence that tissue-specific expression of bacterial phytase can lead to the reduction of phytic acid in rice seeds without hampering its other physiological processes and phenotypic cost.

Genetically engineered rice with appA gene enhanced phosphorus and minerals

Phytic acid or Myo-inositol hexakisphosphate is an essential compound for the rice plants. It remains in the form of phytate, a mixed salt of different mineral cations, in the seeds. The phytate breaks down during germination and provides the inorganic phosphorus and mineral ions to the seedlings. However, humans do not get the benefit of those essential ions from rice consumption due to the absence of phytase in the gut. We envisaged down-regulating ITPK, the gene behind the phytic acid biosynthesis so that its low amount would facilitate a greater amount of free mineral ions in the endosperm. Since there are six homologues of rice ITPK, we studied their expression in seeds. Additionally, we undertook an in-silico analysis of the homologous proteins. Considering the results, we selected ITPK-2 for its RNAi-mediated embryo-specific down-regulation to obtain the low phytate rice. We obtained a 37% reduction of phytic acid content accompanied by a nearly three-fold enhancement of inorganic phosphorus in the transgenic seeds. Additionally, the iron and zinc content increased in polished rice grains compared to the wild type. The results also showed that reduced phytic acid content did not affect the germination potential and seedling growth of the transgenic rice.

RNAi-mediated down-regulation of ITPK-2 enhanced inorganic phosphorus and minerals in the transgenic rice.

Micronutrient deficiencies of iron, zinc, and vitamin-A are such serious global health issues, that it affects one out of every three people worldwide. The intensity of this “hidden hunger” compels us to acknowledge global nutritional security issues. Plant based food are the most popular and trending choices for people of all rungs of the social ladder. Biofortification is a sustainable and promising process of improving nutrition in plant based food through different agronomic approaches, conventional plant breeding and genetic engineering. Biofortified crops have been developed with high iron, high zinc, vitamin-A, with other nutritional quality enhancements and these crops have already proved to be a ‘boon for nutritional security’. This review highlights some selected Biofortified crops with special reference to rice ( Oryza sativa ), as 50% of the global population relies on it.

Shinjini Sengupta

Papers

RNAi-Mediated Silencing of ITPK Gene Reduces Phytic Acid Content, Alters Transcripts of Phytic Acid Biosynthetic Genes, and Modulates Mineral Distribution in Rice Seeds

Genetically engineered rice with appA gene enhanced phosphorus and minerals

RNAi-mediated down-regulation of ITPK-2 enhanced inorganic phosphorus and minerals in the transgenic rice.

Biofortified Crops – Boon for Nutritional Security