The Protein Response Mechanism of Adventitious Root Formation About Scaly Branches in Platycladus orientalis

Platycladus orientalis (P. orientalis) is a monoecious and evergreen tree. It is not only one of the most common ornamental species, but also has some pratical value. Cutting propagation is a common technique used to preserve excellent P. orientalis resources. But the rooting rate is influenced by both internal and external factors. In this study, we used our new cultivar "Liye" as the material to design experiment. We detected the determination of physiological indicators including soluble protein, peroxidase (POD), polyphenol oxidase (PPO), and indole acetic acid oxidase (IAAO). Meanwhile, the content of indole-3-acetic acid (IAA), zeatin riboside (ZR), abscisic acid (ABA), and gibberellin 3 (GA₃) were detected after indole-3-butyric acid (IBA) treatment. According to the data on phenotypic changes, we analyzed some proteins related with hormones by isobaric tag for relative absolute quantitation (iTRAQ). We found IAA is a key endogenous hormone that induced the formation of adventitious root in young branches of P. orientalis. Besides, the content of ZR, ABA, and GA₃ showed the different trends of change. We found 136 differential expression proteins related to hormones, and selected two proteins related to cytokinin, three proteins related to auxin, and one protein related to abscisic acid based on the changing trends of hormone content at different stages. The results provided a more holistic view of cellular processes and laid a theoretical foundation for the production of uniform and high quality seedlings in P. orientalis.