Uncovering protein regulation during adventitious root formation in Platycladus orientalis cuttings.

This article focuses on the cellular basis and physiological regulation of adventitious root (AR) formation in stem cuttings of Platycladus orientalis, an ecologically important coniferous species in China. The study demonstrates that AR primordia originate mainly from cortical parenchyma cells during direct rooting induced by lower concentrations of indole-3-butyric acid (IBA) and from undifferentiated xylem cells during indirect rooting involving callus formation at higher IBA concentrations. Dynamic changes in soluble protein content and enzyme activities—peroxidase (POD), polyphenol oxidase (PPO), and indole acetic acid oxidase (IAAO)—were closely associated with AR development, with POD and PPO activities positively and IAAO activity negatively correlated with root initiation. Proteomic analysis using tandem mass tag (TMT) technology identified 4,265 proteins, including hormone-related and oxidase proteins, which co-regulate AR primordium formation and regeneration, leading to a proposed regulatory network model. These findings provide a molecular and physiological framework to improve clonal propagation techniques for P. orientalis.