Rare-cold-inducible (RCI2) genes are structurally conserved members that encode small, highly hydrophobic proteins involved in response to various abiotic stresses. Phylogenetic and functional analyses of these genes have been conducted in Arabidopsis, but an extensive investigation of the RCI2 gene family has not yet been carried out in maize. In the present study, 10 RCI2 genes were identified in a fully sequenced maize genome. Structural characterization and expression pattern analysis of 10 ZmRCI2s (Zea mays RCI2 genes) were subsequently determined. Sequence and phylogenetic analyses indicated that ZmRCI2s are highly conserved, and most of them could be grouped with their orthologues from other organisms. Chromosomal location analysis indicated that ZmRCI2s were distributed unevenly on seven chromosomes with two segmental duplication events, suggesting that maize RCI2 gene family is an evolutionarily conserved family. Putative stress-responsive cis-elements were detected in the 2-kb promoter regions of the 10 ZmRCI2s. In addition, the 10 ZmRCI2s showed different expression patterns in maize development based on transcriptome analysis. Further, microarray and quantitative real-time PCR (qRT-PCR) analysis showed that each maize RCI2 genes were responsive to drought stress, suggesting their important roles in drought stress response. The results of this work provide a basis for future cloning and application studies of maize RCI2 genes.

NAC transcription factors comprise a large plant-specific gene family. Increasing evidence suggests that members of this family have diverse functions in plant growth and development. In this study, we performed a genomewide survey of NAC type genes in maize (Zea mays L.). A complete set of 148 nonredundant NAC genes (ZmNAC1–ZmNAC148) were identified in the maize genome using Blast search tools, and divided into 12 groups (a–l) based on phylogeny. Chromosomal location of these genes revealed that they are distributed unevenly across all 10 chromosomes. Segmental and tandem duplication contributed largely to the expansion of the maize NAC gene family. The 𝐾_a/𝐾_s ratio suggested that the duplicated genes of maize NAC family mainly experienced purifying selection, with limited functional divergence after duplication events. Microarray analysis indicated most of the maize NAC genes were expressed across different developmental stages. Moreover, 19 maize NAC genes grouped with published stress-responsive genes from other plants were found to contain putative stress-responsive cis-elements in their promoter regions. All these stress-responsive genes belonged to the group d (stress-related). Further, these genes showed differential expression patterns over time in response to drought treatments by quantitative real-time PCR analysis. Our results reveal a comprehensive overview of the maize NAC, and form the foundation for future functional research to uncover their roles in maize growth and development.