Genetic coupling of leaf and kernel-related traits shapes drought adaptation in maize

The source-sink balance between leaf-based source tissues and grain reproductive sink tissues largely governs crop yield and is highly vulnerable to abiotic stress. Few studies have been conducted to uncover the genetic mechanisms behind this relationship under stress. Herein, we dissect the genetic architecture for the source (leaf characteristics) and the sink (kernel characteristics) under two water conditions in Zea mays by integrating genome-wide association study (GWAS), linkage mapping, and RNA-seq. A total of 44 QTLs and 22 QEIs were identified by both GWAS and linkage mapping, including 29 QTLs and 12 QEIs co-locating for source and sink traits, allowing the identification of several promising drought-tolerant candidate genes. Among them, GRMZM2G466044 (ZmEREB195) encodes an ethylene-responsive transcription factor that is differentially expressed in leaves after drought treatment. Phenotyping of two mutants of ZmEREB195 showed that source-related traits, such as chlorophyll content and leaf area, were significantly higher after drought treatment than those of the wild type, thus increasing accumulation in the sink organ and producing larger kernels. Our study provides candidate genes for in-depth analysis of drought tolerance mechanisms during the flowering stage under field water stress, offering new insights into the mechanisms underlying coordinated source-sink responses to drought in maize.