Supplemental Material for He et al., 2020 HeCheng DuYicong FuJunjie ZengErliang ParkSunghun WhiteFrank ZhengJun LiuSanzhen 2020 Time-course gene expression data of maize seedlings under drought were used to identify drought responsive genes, their time-series expression patterns, and which drought stages, namely, early, middle, and late, responses occurred. As compared with later responsive genes, a higher proportion of genes with copy number variation were found in early and middle responsive genes, and their sequence variation is more associated with levels of drought tolerance. With small RNA time-course expression data from the same samples, interactions between genes and small RNAs were investigated to understand transcriptomic regulation upon progressive drought stress.