Genome-Wide Identification, Characterization, and Expression Analysis of the Copper-Containing Amine Oxidase Gene Family in Mangrove Kandelia obovata

Copper-containing amine oxidases (CuAOs) are known to have significant involvement in the process of polyamine catabolism, as well as serving crucial functions in plant development and response to abiotic stress. A genome-wide investigation of the CuAO protein family was previously carried out in sweet orange (Citrus sinensis) and sweet cherry (Prunus avium L.). Six CuAO (KoCuAO1-KoCuAO6) genes were discovered for the first time in the Kandelia obovata (Ko) genome through a genome-wide analysis conducted to better understand the key roles of the CuAO gene family in Kandelia obovata. This study encompassed an investigation into various aspects of gene analysis, including gene characterization and identification, subcellular localization, chromosomal distributions, phylogenetic tree analysis, gene structure analysis, motif analysis, duplication analysis, cis-regulatory element identification, domain and 3D structural variation analysis, as well as expression profiling in leaves under five different treatments of copper (CuCl2). Phylogenetic analysis suggests that these KoCuAOs, like sweet cherry, may be subdivided into three subgroups. Examining the chromosomal location revealed an unequal distribution of the KoCuAO genes across four out of the 18 chromosomes in Kandelia obovata. Six KoCuAO genes have coding regions with 106 and 159 amino acids and exons with 4 and 12 amino acids. Additionally, we discovered that the 2.5 kb upstream promoter region of the KoCuAOs predicted many cis elements linked to phytohormones and stress responses. According to the expression investigations, CuCl2 treatments caused up- and downregulation of all six genes. In conclusion, our work provides a comprehensive overview of the expression pattern and functional variety of the Kandelia obovata CuAO gene family, which will facilitate future functional characterization of each KoCuAO gene.