Genetic variation at transcription factor binding sites largely explains phenotypic heritability in maize

Comprehensive maps of functional variation at transcription factor (TF) binding sites ( cis -elements) are crucial for elucidating how genotype shapes phenotype. Here we report the construction of a pan-cistrome of the maize leaf under well-watered and drought conditions. We quantified haplotype-specific TF footprints across a pan-genome of 25 maize hybrids and mapped over two-hundred thousand genetic variants (termed binding-QTL) linked to cis -element occupancy. Three lines of evidence support the functional significance of binding-QTL: i) they coincide with numerous known causative loci that regulate traits, including VGT1 , Trehalase1 , and the MITE transposon near ZmNAC111 under drought; ii) their footprint bias is mirrored between inbred parents and by ChIP-seq; iii) partitioning genetic variation across genomic regions demonstrates that binding-QTL capture the majority of heritable trait variation across ∼70% of 143 phenotypes. Our study provides a promising approach to make previously hidden cis -variation more accessible for genetic studies and multi-target engineering of complex traits.