Mechanistic insights into adventitious root formation in Cinnamomum kanehirae stem cuttings based on phenotypic, physiological, and transcriptomic analyses

Cinnamomum kanehirae is a species of high economic worth, as it produces abundant aromatic oils for industrial use and its heartwood acts as an optimal substrate for cultivating the medicinal fungus Antrodia cinnamomea. The limited understanding of the underlying molecular and physiological mechanisms restricts the successful propagation of C. kanehirae. This study systematically investigated adventitious roots (ARs) formation in C. kanehirae through anatomical observation, physiological measurement, and transcriptomic analysis. Anatomical results demonstrated that ARs originate from callus tissue and develop through three distinct stages: callus formation, root primordium initiation, and root elongation. Nutrient metabolites, enzyme activities, and endogenous hormones play crucial roles in these processes. A notable decline in soluble sugar content during early AR formation indicated intensive energy utilization for cell division. During root primordium initiation and AR elongation, fluctuations in malondialdehyde levels and the activities of superoxide dismutase and peroxidase reflected the complex regulatory role in oxidative stress in root induction. Transcriptomic analysis identified differentially expressed genes that were significantly enriched in hormone signal transduction, energy metabolism, and circadian rhythm pathways. Auxin and abscisic acid emerged as central regulators within the hormone signaling network. Weighted gene co-expression network analysis further identified hub genes, including CkPYL4, CkOPR2, CkOFP7, CkMYB306, and CkRbohA, involved in hormonal signaling and redox regulation. These findings elucidate the coordinated anatomical, physiological, and molecular mechanisms governing AR formation in C. kanehirae, establishing a theoretical foundation for improving cutting propagation in woody plants.