Modulation of Terpenoid Indole Alkaloid Biosynthesis in Catharanthus roseus by Sphingomonas Sp Y503 via the CrMAPKKK1‐CrMAPKK1/CrMAPKK2‐CrMPK3 Signaling Cascade

ABSTRACT Catharanthus roseus is a highly relevant model for investigating plant defense mechanisms and the biosynthesis of therapeutically valuable compounds, including terpenoid indole alkaloids (TIAs). It has been demonstrated that beneficial microbial interactions can regulate TIA biosynthesis in C. roseus , highlighting the need to fully comprehend the molecular mechanisms involved to efficiently implement eco‐friendly strategies. This study explores the effects of a novel microbial strain, Y503, identified as Sphingomonas sp., on TIA production and the underlying mechanisms in C. roseus . Through bioinformatics analysis, we have identified 17 MAPKKKs, 7 MAPKKs, and 13 MAPKs within the C. roseus genome. Further investigation has verified the presence of the MAPK module (CrMAPKKK1‐CrMAPKK1/CrMAPKK2‐CrMPK3) mediating Y503 in regulating TIA biosynthesis in C. roseus . This study provides foundational information for strengthening the plant defense system in C. roseus through advantageous microbial interactions, which could contribute to the sustainable cultivation of medicinal plants such as C. roseus .