RNA Sequencing Analysis and Verification of Paeonia ostii 'Fengdan' CuZn Superoxide Dismutase (PoSOD) Genes in Root Development

Tree peony (Paeonia suffruticosa) is a significant medicinal plant. However, the low rooting number is a bottleneck problem in the micropropagation protocols of P. ostii 'Fengdan'. The activity of superoxide dismutase (SOD) is closely related to root development. But research on the SOD gene's impact on rooting is still lacking. In this study, RNA sequencing (RNA-seq) was used to analyze the four crucial stages of root development in P. ostii 'Fengdan' seedlings, including the early root primordium formation stage (Gmfq), root primordium formation stage (Gmf), root protrusion stage (Gtq), and root outgrowth stage (Gzc). A total of 141.77 GB of data were obtained; 71,718, 29,804, and 24,712 differentially expressed genes (DEGs) were identified in the comparison groups of Gmfq vs. Gmf, Gmf vs. Gtq, and Gtq vs. Gzc, respectively. Among the 20 most highly expressed DEGs in the three comparison groups, only the CuZnSOD gene (SUB13202229, PoSOD) was found to be significantly expressed in Gtq vs. Gzc. The overexpression of PoSOD increased the number of adventitious roots and promoted the activities of peroxidase (POD) and SOD in P. ostii 'Fengdan'. The gene ADVENTITIOUS ROOTING RELATED OXYGENASE1 (PoARRO-1), which is closely associated with the development of adventitious roots, was also significantly upregulated in overexpressing PoSOD plants. Furthermore, PoSOD interacted with PoARRO-1 in yeast two-hybrid (Y2H) and biomolecular luminescence complementation (BiFC) assays. In conclusion, PoSOD could interact with PoARRO-1 and enhance the root development of tube plantlets in P. ostii 'Fengdan'. This study will help us to preliminarily understand the molecular mechanism of adventitious root formation and improve the root quality of tree peony and other medicinal plants.