Abstract
The plant-specific INDETERMINATE DOMAIN (IDD) gene family is important for plant growth and development. However, a comprehensive analysis of the IDD family in orchids is limited. Based on the genome data of Phalaenopsis equestris, the IDD gene family was identified and analyzed by bioinformatics methods in this study. Ten putative P. equestris IDD genes (PeIDDs) were characterized and phylogenetically classified into two groups according to their full amino acid sequences. Protein motifs analysis revealed that overall structures of PeIDDs in the same group were relatively conserved. Its promoter regions harbored a large number of responsive elements, including light responsive, abiotic stress responsive elements, and plant hormone cis-acting elements. The transcript level of PeIDD genes under cold and drought conditions, and by exogenous auxin (NAA) and abscisic acid (ABA) treatments further confirmed that most PeIDDs responded to various conditions and might play essential roles under abiotic stresses and hormone responses. In addition, distinct expression profiles in different tissues/organs suggested that PeIDDs might be involved in various development processes. Furthermore, the prediction of protein-protein interactions (PPIs) revealed some PeIDDs (PeIDD3 or PeIDD5) might function via cooperating with chromatin remodeling factors. The results of this study provided a reference for further understanding the function of PeIDDs.