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

## TL;DR

A gene called AcPRX12 helps shape the daughter roots of Aconitum carmichaelii by promoting lignin production, which affects root structure and medicinal quality.

## Contribution

The study identifies AcPRX12 as a key gene regulating daughter root morphogenesis through lignin synthesis in Aconitum carmichaelii.

## Key findings

- AcPRX12 expression is higher in non-swollen root regions and correlates with lignin accumulation.
- Heterologous expression of AcPRX12 in Arabidopsis increases lignin content and alters plant morphology.
- The gene encodes a peroxidase with predicted affinity for lignin monomers, supporting its role in lignin biosynthesis.

## Abstract

Research on the diterpenoid alkaloids of Aconitum carmichaelii Debx. has been relatively extensive, yet systematic studies on the development of its daughter roots remain limited. The daughter root serves as both the direct source of the medicinal material “Fuzi” and the vegetative propagation material, and its morphogenesis directly affects the yield and quality of the medicinal products. This study focused on key factors regulating the morphology of the daughter root and found that the expression of the peroxidase gene AcPRX12 was consistently higher in non-swollen regions than in swollen regions of the daughter root, with its expression pattern aligning with the trend of lignin accumulation. The full-length transcript of AcPRX12 was obtained using RACE technology, and bioinformatics analysis suggested that the encoded protein is likely involved in lignin biosynthesis. Heterologous expression of AcPRX12 in Arabidopsis significantly increased lignin content and inhibited plant growth, further confirming that this gene influences organ morphology by regulating lignin synthesis.

Although the diterpenoid alkaloids of Aconitum carmichaelii 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 A. carmichaelii as experimental material. Quantitative real-time polymerase chain reaction (qRT-PCR) and total lignin quantification demonstrated that both the expression level of AcPRX12 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 AcPRX12 (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 AcPRX12 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 AcPRX12 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 AcPRX12, offering a key gene resource and a theoretical basis for understanding its morphogenesis.