Comparative analysis of root anatomy, phytochemicals and gene expression in bolted and unbolted Saposhnikovia divaricata

Saposhnikovia divaricata (Turcz.) Schischk., known as Fangfeng, is a highly valued traditional Chinese medicinal herb esteemed for its therapeutic properties. Premature bolting in S. divaricata adversely affects root yield and medicinal quality. This study aimed to compare root anatomical structures, active phytochemical contents, and gene expression differences between unbolted (UBF) and bolted (BF) S. divaricata plants, which can provide a theoretical foundation for elucidating potential mechanisms driving premature bolting for future research and practical applications. The result showed that UBF roots exhibited intact secondary xylem and wider secondary phloem, whereas BF roots showed fragmented secondary xylem with lignified parenchyma cells. Chromone concentrations were higher in UBF plants, particularly within the secondary phloem. Transcriptome analysis identified 33 differentially expressed genes (DEGs) associated with bolting and flowering, 22 DEGs involved in plant hormone signal transduction pathways, including ETR, JAR1, EIN3, TCH4, GID2, ABF, BKI1, BSK, BIN, BZR1/2, CYCD3, and 11 DEGs involved in circadian rhythm pathways, including GI, ZTL, FT, PHYA, COP1, SPA, FKF1, were differentially expressed between BF and UBF groups, suggesting their potential role in regulating bolting and flowering in S. divaricata. These findings suggest that plant hormones and circadian rhythms may influence bolting and flowering in S. divaricata. These findings can provide a theoretical basis for analyzing the mechanisms of bolting and flowering in this species and the Apiaceae family. However, premature bolting adversely affects root quality, necessitating further investigation into its regulatory mechanisms to improve cultivation practices.