Iron Biofortification in Rice: An Update on Quantitative Trait Loci and Candidate Genes.

B P Mallikarjuna Swamy,Balram Marathi,Mark Ian C Calayugan,Felipe Klein Ricachenevsky,Ana I F Ribeiro-Barros

doi:10.3389/fpls.2021.647341

Abstract

Rice is the most versatile model for cereals and also an economically relevant food crop; as a result, it is the most suitable species for molecular characterization of Fe homeostasis and biofortification. Recently there have been significant efforts to dissect genes and quantitative trait loci (QTL) associated with Fe translocation into rice grains; such information is highly useful for Fe biofortification of cereals but very limited in other species, such as maize (Zea mays) and wheat (Triticum aestivum). Given rice’s centrality as a model for Poaceae species, we review the current knowledge on genes playing important roles in Fe transport, accumulation, and distribution in rice grains and QTLs that might explain the variability in Fe concentrations observed in different genotypes. More than 90 Fe QTLs have been identified over the 12 rice chromosomes. From these, 17 were recorded as stable, and 25 harbored Fe-related genes nearby or within the QTL. Among the candidate genes associated with Fe uptake, translocation, and loading into rice grains, we highlight the function of transporters from the YSL and ZIP families; transporters from metal-binding molecules, such as nicotianamine and deoxymugineic acid; vacuolar iron transporters; citrate efflux transporters; and others that were shown to play a role in steps leading to Fe delivery to seeds. Finally, we discuss the application of these QTLs and genes in genomics assisted breeding for fast-tracking Fe biofortification in rice and other cereals in the near future.

Highlights

Hidden hunger affects more than two billion people worldwide and is among the major challenges to be addressed on a priority basis to achieve Zero Hunger, in African, Asian, and Latin-American countries
Besides IDA, other types of anemia may be related to (i) active bleeding related to menstruation, wounding, gastrointestinal ulcers, and cancer; (ii) kidney disease related to the decrease in the hormone erythropoietin, involved in the production of red blood cells; (iii) obesity-related systemic inflammation that increases hepcidin, reducing Fe availability; (iv) alcoholism; and (v) sickle cell anemia and thalassemia, two genetically inherited diseases related to the abnormal production of hemoglobin (Abbaspour et al, 2014)
We summarize the current knowledge of quantitative trait loci (QTL) identified in multiple studies using different genotypes and review the known genes associated with Fe delivery and accumulation in rice grains

Summary

Introduction

Hidden hunger affects more than two billion people worldwide and is among the major challenges to be addressed on a priority basis to achieve Zero Hunger, in African, Asian, and Latin-American countries. Plants that have no functional MIR are unable to properly regulate Fe levels as they accumulate more Fe in roots, shoots, and seeds while having constitutively high expression of Fe uptake genes (Ishimaru et al, 2009).

Results

Conclusion