Physiological and transcriptome analyses for revealing the mechanism of adventitious root formation in Camellia luteoflora

Camellia luteoflora is a plant species endemic to China, is classified as a rare and endangered plant under Category II protection. This study aims to investigate the mechanism of adventitious roots (ARs) formation during the cutting process of C. luteoflora. This study combines anatomical observation, physiological index measurement, and transcriptome analysis at four stages: initial cutting stage(S1), callus formation stage(S2), ARs formation stage(S3), and ARs elongation stage(S4). The results demonstrated that root primordia of C. luteoflora originated from the phloem, and vascular cambium during ARs induction. In the initial stage of ARs induction, SOD activity was associated with elevated GA3 levels, which may promote ARs differentiation. Meanwhile CAT, PPO, POD, IAAO, ABA, SA, and IAA jointly regulated ARs development through the redox and hormone signaling networks. Concurrently, higher protein and sugar contents provided the necessary energy substances for ARs elongation. Furthermore, WGCNA identified three key genes modules with distinct regulatory roles in ARs formation: the black module genes (MYB4, MYB48, CYP71D10, bZIP2, POD1-like) were associated with oxidative stress response and positively regulated callus formation; the brown module genes (WRKY23, CYP71A4, CYP704C1, MYB4) enhanced stress resistance via secondary metabolite synthesis, promoting wound healing while potentially inhibiting ARs initiation; and the green module genes (PDC1, ADH, LAC-7, ZOG, ATP-PFK3) activated anaerobic respiration, cell wall modification and glycolysis pathways to positively regulate AR formation. During the induction and development of ARs in C. luteoflora, the origin of adventitious root primordia, physiological and biochemical processes, and hub gene modules all play specific regulatory roles. These findings play a crucial role in understanding ARs development in C. luteoflora, with significant implications for its efficient propagation, conservation of endangered germplasm, exploration of potential applications, and elucidation of the molecular mechanisms underlying rooting.