Point mutation in sensor triples zinc levels in <i>Sorghum bicolor</i>

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.