Abstract
Andrographis paniculata, commonly known as the "King of Bitters," is a medicinal plant valued for its bioactive diterpenoids, particularly andrographolides. Dicer-like (DCL) proteins are central to the miRNA pathway, processing precursor miRNAs into mature miRNAs that regulate gene expression. While miRNAs influence plant metabolism, their role in secondary metabolite biosynthesis in A. paniculata remains unexplored. This study identified and characterized five ApDCL genes, mapped to distinct chromosomes in A. paniculata. The structural analysis revealed that ApDCL3 contained the highest number of introns (24), whereas ApDCL2 had the fewest (10). Conserved RNA-processing domains were confirmed, and phylogenetic analysis revealed evolutionary conservation, showing that ApDCLs are closely related to the DCLs of Sesamum indicum and Salvia miltiorrhiza. Expression analysis showed ApDCL1 and ApDCL2 were predominantly expressed in roots, whereas ApDCL3, ApDCL4a, and ApDCL4b were more abundant in leaves. Methyl jasmonate treatment upregulated ApDCL3 (~ 3.5-fold) and ApDCL4a (~ 1.5-fold), but further research is needed to determine whether this response directly influences secondary metabolism or results from MeJ-induced stress. These findings provide a foundation for functional validation through gene knockdown, overexpression, and CRISPR-Cas-based genome editing to elucidate DCL-mediated regulatory mechanisms. Future research leveraging these insights could aid in modulating RNA silencing pathways to enhance the biosynthesis of pharmacologically significant metabolites in A. paniculata through biotechnological interventions.