The Peroxidase12 Gene Regulates Morphogenesis of the Daughter Root of Aconitum carmichaelii Debx. by Promoting Lignin Synthesis

Although the diterpenoid alkaloids of <i>Aconitum carmichaelii</i> Debx. have long been a research focus in phytochemistry and pharmacology, systematic studies on the growth and development of its daughter roots remain limited, yet this process critically determines the yield and quality of the medicinal material. This study utilized the Jiangyou-derived daughter root of <i>A. carmichaelii</i> as experimental material. Quantitative real-time polymerase chain reaction (qRT-PCR) and total lignin quantification demonstrated that both the expression level of <i>AcPRX12</i> and total lignin relative content were consistently higher in the non-swollen (PB) parts than in the swollen (P) parts of the daughter roots. The complete cDNA sequence of the <i>AcPRX12</i> (with a full length of 1357 bp and encoding 350 amino acids) was obtained by rapid amplification of cDNA ends (RACE). Bioinformatics analysis identified AcPRX12 as an extracellular class III peroxidase containing a secretory peroxidase domain, and further predicted its strong binding affinity for syringaldazine, an S-type lignin monomer analog. In addition, the heterologous expression of <i>AcPRX12</i> in Arabidopsis thaliana resulted in a significant increase in lignin content, which inhibited plant growth, as evidenced by shorter roots, thinner stems, smaller leaves, and shorter siliques. Collectively, these results support a model in which <i>AcPRX12</i> promotes lignin biosynthesis to modulate daughter root development, ultimately shaping its distinctive tapered morphology. In conclusion, our findings propose a lignin-mediated regulatory mechanism for daughter root development controlled by <i>AcPRX12</i>, offering a key gene resource and a theoretical basis for understanding its morphogenesis.