Dissection of Molecular Processes and Genetic Architecture Underlying Iron and Zinc Homeostasis for Biofortification: From Model Plants to Common Wheat

Abstract

The micronutrients iron (Fe) and zinc (Zn) are not only essential for plant survival and proliferation but are crucial for human health. Increasing Fe and Zn levels in edible parts of plants, known as biofortification, is seen a sustainable approach to alleviate micronutrient deficiency in humans. Wheat, as one of the leading staple foods worldwide, is recognized as a prioritized choice for Fe and Zn biofortification. However, to date, limited molecular and physiological mechanisms have been elucidated for Fe and Zn homeostasis in wheat. The expanding molecular understanding of Fe and Zn homeostasis in model plants is providing invaluable resources to biofortify wheat. Recent advancements in NGS (next generation sequencing) technologies coupled with improved wheat genome assembly and high-throughput genotyping platforms have initiated a revolution in resources and approaches for wheat genetic investigations and breeding. Here, we summarize molecular processes and genes involved in Fe and Zn homeostasis in the model plants Arabidopsis and rice, identify their orthologs in the wheat genome, and relate them to known wheat Fe/Zn QTL (quantitative trait locus/loci) based on physical positions. The current study provides the first inventory of the genes regulating grain Fe and Zn homeostasis in wheat, which will benefit gene discovery and breeding, and thereby accelerate the release of Fe- and Zn-enriched wheats.

QTL Mapping for Grain Zinc and Iron Concentrations in Bread Wheat

“…Gorafi et al ( 32 ) identified a significant and positive phenotypic correlation between GZn and GFe ( r = 0.78) and a pleiotropic QTL on chromosome 5D; significant and positive correlations between GZn and GFe were also found in other studies ( 11 , 42 ). It has been reported that some transporters, chelators, and genes regulated GZn and GFe simultaneously in a high frequency ( 10 , 43 ). These findings indicated that Zn and Fe could be improved simultaneously in breeding programs targeting mineral biofortification.…”

“…Fe deficiency in humans most commonly leads to nutritional anemia in women and children ( 8 ). Therefore, it is very important to improve the nutritional quality of wheat by enhancing the Zn (GZn) and Fe (GFe) concentrations in grain ( 9 , 10 ).…”

Biofortification of major crop plants with iron and zinc - achievements and future directions

“…Thirty-nine (Raney et al 2013;Andersson et al 2017;Bouis et al 2020) marker trait associations were identified for Zn on chromosomes 2 and 7 (Velu et al 2018b). As Fe and Zn concentration of crops is controlled by a large number of loci, it is currently challenging to implement the findings in breeding programs, so more precision is required to discover the exact regions responsible for Fe and Zn concentration and to give an indication of variation in these markers and their potential effectiveness in breeding (Tong et al 2020). The complete haplotype-block based method could be more effective and practical (Ali and Borrill 2020).…”

High Resolution Genome Wide Association Studies Reveal Rich Genetic Architectures of Grain Zinc and Iron in Common Wheat (Triticum aestivum L.)

“…To improve our understanding of the genetic basis of wheat grain Zn and Fe, identification of as many causal loci as possible is imperative ( Tong et al, 2020 ). In recent years, diverse bi-parental populations have been used to identify quantitative trait locus/loci (QTL) associated with grain Zn (GZnC) and Fe concentrations (GFeC) in common wheat and its relative species ( Tong et al, 2020 ; Gupta et al, 2021 ).…”