Transcriptomic and metabolomic analyses provide new insights into the appropriate harvest period in regenerated bulbs of .

INTRODUCTION

The bulb of , a traditional cough and expectorant medicine, is usually harvested from June to September according to traditional cultivation experience, without practical scientific guidance. Although steroidal alkaloid metabolites have been identified in , the dynamic changes in their levels during bulb development and their molecular regulatory mechanisms are poorly understood.

METHODS

In this study, integrative analyses of the bulbus phenotype, bioactive chemical investigations, and metabolome and transcriptome profiles were performed to systematically explore the variations in steroidal alkaloid metabolite levels and identify the genes modulating their accumulation and the corresponding regulatory mechanisms.

RESULTS

The results showed that weight, size, and total alkaloid content of the regenerated bulbs reached a maximum at IM03 (post-withering stage, early July), whereas peiminine content reached a maximum at IM02 (withering stage, early June). There were no significant differences between IM02 and IM03, indicating that regenerated bulbs could be harvested appropriately in early June or July. Peiminine, peimine, tortifoline, hupehenine, korseveramine, delafrine, hericenone N-oxide, korseveridine, puqiedinone, pingbeinone, puqienine B, puqienine E, pingbeimine A, jervine, and ussuriedine levels were upregulated in IM02 and IM03, compared with IM01 (vigorous growth stage, early April). The Kyoto Encyclopedia of Genes and Genomes enrichment analysis indicated that the accumulation of steroidal alkaloid metabolites mainly occurred prior to IM02. , , , , and may play a positive role in peiminine, peimine, hupehenine, korseveramine, korseveridine, hericenone N-oxide, puqiedinone, delafrine, tortifoline, pingbeinone, puqienine B, puqienine E, pingbeimine A, jervine, and ussuriedine biosynthesis, whereas the downregulation of , and may lead to a reduction in peimisine levels. Weighted gene correlation network analysis showed that , , and were negatively correlated with peiminine and pingbeimine A, whereas and were positively correlated. and may play a negative role in peimine and korseveridine biosynthesis, whereas plays a positive role. In addition, the highly expressed C2H2, HSF, AP2/ERF, HB, GRAS, C3H, NAC, MYB-related transcription factors (TFs), GARP-G2-like TFs, and WRKY may play positive roles in the accumulation of peiminine, peimine, korseveridine, and pingbeimine A.

DISCUSSION

These results provide new insights into scientific harvesting of .