Genetic Control of Iron Bioavailability is Independent from Iron Concentration in a Diverse Winter Wheat Mapping Population

Abstract

Background: Anemia is thought to affect up to 1.6 billion people worldwide. One of the major contributors to low iron (Fe) absorption is a higher proportion of cereals compared to meats and pulse crops in people’s diets. This has now become a problem in both the developed and developing world, as a result of both modern food choice and food availability. Bread wheat accounts for 20% of the calories consumed by humans and is an important source of protein, vitamins and minerals meaning it could be a major vehicle for bringing more bioavailable Fe into the diet. Results: To investigate whether breeding for higher concentrations of Fe in wheat grains could help increase Fe absorption, a multiparent advanced generation intercross (MAGIC) population, encompassing more than 80% of UK wheat polymorphism, was grown over two seasons in the UK. The population was phenotyped for both Fe concentration and Fe bioavailability using an established Caco-2 cell bioassay. It was found that increasing Fe levels in the grains was not correlated with higher Fe bioavailability and that the underlying genetic regions controlling grain Fe levels do not co-localise with increased Fe absorption. Furthermore, we show that phytate levels do not correlate with Fe bioavailability in our wheat population and thus phytate-binding is insufficient to explain the lack of correlation between Fe bioavailability and Fe concentrations in the wheat grain. Finally, we observed no (Fe bioavailability) or low (Fe concentration) correlation between years for these traits, confirming that both are under strong environmental influence. Conclusions: This suggests that breeders will have to select not only for Fe levels directly in grains, but also increased bioavailability.

Strategies and Bottlenecks in Hexaploid Wheat to Mobilize Soil Iron to Grains

“…The foremost reason for this is that even though Fe content in the whole seed is increased, it is stored in the aleurone layer which gets removed while milling, leaving only the endosperm for consumption. Therefore, both Fe content and bioavailability should be taken into account while addressing the biofortification of wheat (Eagling et al, 2014;Wright et al, 2021). To further address this, the wheat genome was studied for the identification of the QTLs that could be responsible for both high Fe-content and bioavailability (Wright et al, 2021).…”

“…Therefore, both Fe content and bioavailability should be taken into account while addressing the biofortification of wheat (Eagling et al, 2014;Wright et al, 2021). To further address this, the wheat genome was studied for the identification of the QTLs that could be responsible for both high Fe-content and bioavailability (Wright et al, 2021). Very recently, a two-gene strategy to overexpress VIT-NAS in wheat endosperm showed high Fe concentration and also improves mineral bioaccessibility (Harrington et al, 2022).…”

Whole-Genome Sequencing and Analysis of Nutritional Traits in a Core Set of Ethiopian Teff (Eragrostis tef) Varieties

“…It is often reported that phytate inhibits Fe bioavailability, so the negative correlation between Fe and phytate levels in teff could prove bene cial. While future research is requiredto determine whether elevated levels of phenolics that stimulate and inhibit Fe uptake in the human gut can help alleviate the anaemia seen in Ethiopian children [69], the signi cance of the SNP in the teff F3'H gene Et_s3159-0.29-1.mrna1,which explainsa large proportion of the variation in kaempferol glycoside and quercetin glycoside levels, suggest this might be a breeding target to improve Fe bioavailability in teff, as kaempferol glycoside is known to promote Fe absorption while quercetin glycoside inhibits Fe absorption in cell assays [60].In addition, phenolic compounds have also been found to in uence other agronomic traits, including tolerance to both biotic and abiotic stress [14,60,61,68].…”

“…Recent advancements in our understanding of the genetics of teff include a fairly complete genome assembly, the release of gene models,as well as a number of RNASeq datasets which are all publicly available [9]. These allow for translation of knowledge on grain forti cation from other species, supporting more rapid advancements in efforts to improve the nutritionalpotentialofteff [10][11][12][13][14].…”