Phylogenetic Analysis of the Gene Family in Euphorbiaceae and Its Expression Profiles in Tung Tree ().

Pathogenesis-related protein-4 () is generally believed to be involved in physiological processes. However, a comprehensive investigation of this protein in tung tree () has yet to be conducted. In this study, we identified 30 genes in the genomes of Euphorbiaceae species and investigated their domain organization, evolution, promoter cis-elements, expression profiles, and expression profiles in the tung tree. Sequence and structural analyses indicated that and in the tung tree could be classified as belonging to Class II and I, respectively. Phylogenetic and Ka/Ks analyses revealed that exhibited a significantly expanded number of genes. Additionally, the analysis of promoter cis-elements suggested that two genes may play a role in the response to hormones and biotic and abiotic stress of tung trees. Furthermore, the expression patterns of genes and their responses to 6-BA, salicylic acid, and silver nitrate in inflorescence buds of tung trees were evaluated using qRT-PCR. Notably, the expression of two genes was found to be particularly high in leaves and early stages of tung seeds. These results suggest that and may have significant roles in the development of leaves and seeds in tung trees. Furthermore, these genes were found to be responsive to 6-BA, salicylic acid, and silver nitrate in the development of inflorescence buds. This research provides valuable insights for future investigation into the functions of genes in tung trees.