Genome-wide analysis of the IQD gene family in maize.

IQD gene family plays important roles in plant developmental processes and stress responses. To date, no systematic characterization of this gene family has been carried out in maize. In this study, 26 IQD genes, from ZmIQD1 to ZmIQD26, were identified using Blast search tools. The phylogenetic analysis showed these genes were divided into four subfamilies (IQD I-IV) and members within the same subfamily shared conserved exon/intron distribution and motif composition. The 26 ZmIQD genes are distributed unevenly on 8 of the 10 chromosomes, with 9 segmental duplication events, suggesting that the expansion of IQDs in maize was due to the segmental duplication. The analysis of Ka/Ks ratios showed that the duplicated ZmIQDs had primarily undergone strong purifying selection. In addition, the 26 ZmIQDs displayed different expression patterns at different developmental stages of maize based on transcriptome analysis. Further, quantitative real-time PCR analysis showed that all 26 ZmIQD genes were responsive to drought treatment, suggesting their crucial roles in drought stress response. Yeast two-hybrid assay proved that ZmIQD2 and ZmIQD15 can interact with ZmCaM2 and IQ or I in IQ motif is required for ZmIQD15 to combine with CaM2. Our results present a comprehensive overview of the maize IQD gene family and lay an important foundation for further analysis aimed at uncovering the biological functions of ZmIQDs in growth and development.