A SAUR gene enhances maize drought resilience by promoting silk elongation

Drought poses a substantial threat to world food security^1,2. Maize (Zea mays) is a major crop for food and forage, and is particularly susceptible to drought during flowering^3,4. As a monoecious plant species, drought induces asynchronous maturation of male and female inflorescences in maize plants, leading to an increased interval between pollen shedding (anthesis) and silk (elongated stigma and style) exposure (silking)^5,6. This drought-induced anthesis-silking interval (ASI) fundamentally undermines maize yield stability, but the genetic control of the ASI remains largely unknown. Here we report cloning of a quantitative trait locus, Drought Resistance 9 (qDR9), that shortens the drought-increased ASI and enhances the yield stability under drought conditions. The causal gene underlying qDR9 encodes a Small Auxin Up RNA (SAUR) protein (ZmSAUR72) that is highly expressed in maize silks but downregulated under drought. ZmSAUR72 inhibits a plasma membrane-localized protein phosphatase, thereby increasing H⁺-ATPase activity and promoting silk growth. The favourable ZmSAUR72 allele-which lacks a transposon-like insertion in its promoter-drives higher expression, shortens ASI under drought, stabilizes yield and imposes no yield penalty under normal conditions. Thus, our findings offer new insights into maize ASI under drought and provide strong candidate genes to breed maize cultivars with enhanced yield stability under water-deficit conditions.