Integrated phenotypic, phytochemical and transcriptomic analysis reveals shading effects on early bolting in Peucedanum praeruptorum Dunn

Peucedanum praeruptorum Dunn is a perennial and one-time flowering medical plant whose early bolting significantly compromises both yield and quality. Previous research has shown that light conditions play a crucial role in regulating this early bolting phenomenon. In an attempt to elucidate the regulatory mechanism underlying light-mediated bolting in P. praeruptorum, we conducted shading experiments to systematically analyze the dynamic phenotypic variations, phytochemical composition changes, and transcriptomic profiles between early bolting and non-bolting plants under altered light conditions. Results showed that low light effectively inhibited the occurrence of early bolting, but it also significantly suppressed the growth of the plant. Additionally, shading significantly affected the accumulation of active components, the contents of bergapten, praeruptorin A, and praeruptorin E showed a positive correlation with light intensity, while praeruptorin B exhibited an inverse correlation. The 70% shading treatment was identified as the optimal condition, effectively mitigating early bolting while maintaining acceptable levels of plant growth and medicinal quality for P. praeruptorum cultivation. Transcriptome analysis of 96 samples revealed a progressive reduction in both total gene expression and the number of differentially expressed genes as shading intensity increased. Among these, we identified 757 differentially expressed genes significantly associated with early bolting regulation. Notably, 23 candidate genes, including PHYA, FT, bZIP, NAC, ABF, ERF1, At1g72540, CYCD3, FKBP16, DELLA, JAZ, MYC2, SNRK2, and AUX/IAA, were identified as potential regulators of early bolting in response to shading condition. In addition, 11 candidate genes regulating coumarin components were identified, including 4CL, CCR, CSE, CCoaOMT, and the change trends of their expression profiles were consistent with the contents of coumarin components. These findings provide the first empirical evidence for the mechanisms underlying early bolting and quality formation in P. praeruptorum, and offer valuable insights into producing high-quality P. praeruptorum.