Identification and functional characterization of IbSCPL18 regulating anthocyanin acylation and accumulation in sweetpotato

Anthocyanin acylation is a crucial determinant of pigment stability and chemical diversity in purple-fleshed sweetpotato ( Ipomoea batatas ). However, the molecular mechanisms governing this modification remain largely elusive. Here, we characterized a spontaneous mutant (M1–213 M) exhibiting a significant loss-of-anthocyanin phenotype. Targeted metabolomics revealed that this hypopigmentation was primarily attributed to a specific deficiency in acylated anthocyanins. Through comparative transcriptomics, IbSCPL18 , encoding a serine carboxypeptidase-like protein, was identified as a candidate regulator, showing downregulation in the mutant and a strong positive correlation with anthocyanin accumulation across diverse germplasms. Functional validation demonstrated that heterologous overexpression of IbSCPL18 in Petunia hybrida significantly enhanced floral pigmentation. This phenotypic change was metabolically coupled with the accumulation of specific anthocyanin derivatives and the transcriptional activation of endogenous biosynthetic and transporter genes. Collectively, these findings elucidate the role of IbSCPL18 as a positive regulator of anthocyanin acylation and accumulation, providing a valuable genetic target for enhancing the nutritional quality of sweetpotato.