A domestication-selected CIPK-MYB-HAK module improves salt tolerance in modern maize

Domestication has profoundly reshaped the maize genome, yet its impact on abiotic stress resilience remains largely unresolved. Here we show that modern maize exhibits markedly greater salt tolerance than its wild progenitor, teosinte. Using a maize-teosinte (W22-T8759) recombinant inbred line population, we identify the transcriptional repressor MYB28 as a major genetic determinant underlying this divergence. MYB28 negatively regulates salt tolerance by impairing shoot Na⁺ exclusion. In modern maize (W22), however, salt stress activates CIPK20, which phosphorylates MYB28 to relieve its repression. A non-synonymous single nucleotide polymorphism (SNP1409T) disrupts this regulation in teosinte (T8759), conferring salt sensitivity. We further identify HAK4 as a downstream target of the CIPK20-MYB28 pathway, mediating shoot Na⁺ exclusion and salt adaptation. Population genomic and cross-species analyses revealed that the salt-tolerant SNP1409T MYB28 allele originated in ancestral teosinte and was positively selected during domestication, increasing yield in salt-affected fields. Together, our findings uncover a domestication-selected CIPK20-MYB28-HAK4 module that provides mechanistic insights into the evolutionary trajectory of salt tolerance, and identifies valuable targets for developing salt-resilient cultivars.