Comprehensive identification and expression analysis of the CPP gene family in maize (Zea mays L.).

Background: Maize is an important crop. The cysteine-rich polycomb-like protein (CPP) is crucial for plant development and abiotic stress response. However, few reports have been reported on the function of ZmCPPs. This study conducted bioinformatics and expression analyses of the ZmCPP gene family.

Results: Based on the homologous comparison methods, 12 ZmCPPs were identified in the last assembly of maize B73 genome (V5). They were unevenly distributed across six maize chromosomes. Six ZmCPPs formed 3 groups due to segmental but no tandem duplication, indicating segmental duplication as the key driving force of the ZmCPPs family expansion. Homologous evolutionary analysis classified 12 ZmCPPs into three groups, with each containing four members. ZmCPP gene structure and protein motif in the same group were highly conserved. The promoter regions of 12 ZmCPP genes containing plant growth, hormone, and abiotic stress-responsive elements. RNA-seq data indicated that the expression pattern of ZmCPPs exhibited organizational specificity and the ZmCPPs transcript levels could be influenced by abiotic/biotic stresses. RT-qPCR analysis of six ZmCPPs (ZmCPP2/4/8/9/11/12) showed that the expression of ZmCPPs were induced or reduced by short-term heat, cold, dehydration, and waterlogging stresses. Furthermore, ZmCPP2/9 was localized in the cytoplasm and nucleus, without transactivation activity in yeast.

Conclusion: Taken together, the comprehensive analysis of ZmCPPs in the whole genome provides a novel perspective on the evolutionary relationship among ZmCPP genes and lays a foundation for further study of the biological functions of ZmCPPs.