Point mutation in sensor triples zinc levels in Sorghum bicolor

Abstract

Zinc (Zn) deficiency is widespread in agricultural soils and it is also a common nutritional problem in humans. We previously discovered a Zn Sensor Motif (ZSM) in the Arabidopsis F-bZIP transcription factors, bZIP19 and bZIP23, which impacts the concentration of Zn in Arabidopsis plants. Sorghum (Sorghum bicolor (L.) Moench) is one of the most important cereals crops worldwide and here, using a large-scale sorghum mutant library, we report the identification of variants with a ZSM point mutation. We show that a cysteine substitution in the ZSM of the sorghum bZIP19/23 homolog causes a three-fold increase in Zn levels in sorghum seeds with no visible developmental penalty. Our work provides the first evidence that modulating the F-bZIP ZSM is a promising strategy for Zn biofortification in crops. This discovery paves the way to generate Zn biofortified crops and alleviate the global problems of Zn deficient soils and Zn malnutrition.