Science 361, 694–697 (2018)

Maize plants produce secondary metabolites such as benzoxazinoids (BXs), which protect them against insect pests. The western corn rootworm, a specialized maize pest, tolerates and prefers to feed on maize roots with high BX levels. Hu et al. used different maize BX biosynthesis mutants to demonstrate that rootworm larvae prefer roots that produce high amounts of 7-O-methylated, N-hydroxylated BXs such as DIMBOA and DIMBOA-Glc. Surprisingly, BXs themselves were not attractive, but the complexes that form between DIMBOA and iron at the root surface were. The absence of BXs in maize mutants led to iron deficiency in both the plant and the herbivore, suggesting that both require iron–DIMBOA complexes for their development. Finally, the authors identified a DMT-like iron transporter (DvIRT1) required for the rootworm to benefit from maize iron–DIMBOA complexes. Overall, these findings reveal that herbivores can misuse plant micronutrient uptake, which expands the current understanding of plant–herbivore interactions and could inspire new methods for pest management.