Abstract
BACKGROUND: O-methyltransferase (OMT) is an important rate-limiting enzyme that plays a vital role in synthesizing various key metabolites, such as benzylisoquinoline alkaloids (BIA). Nevertheless, there is a dearth of extensive research on the analysis of the OMT gene family in Stephania japonica, a main source of cepharanthine with an anti-coronavirus effect. METHODS: Two OMT family genes, SjCCoAOMT and SjCOMT, were identified from the high-quality genome of S. japonica during this investigation. Further analysis of SjCCoAOMT and SjCOMT genes involved chromosome distribution, gene structure, phylogenetic relationship, conserved motif, expression profile, quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) experiments an d cis-acting elements analysis. RESULTS: There are six SjCCoAOMT members and fifty-two SjCOMT members in the genome of S. japonica, which are unevenly distributed on 11 chromosomes. OMTs could be clustered into SjCCoAOMT and SjCOMT subfamilies through phylogenetic relationship, consistent with the conserved motif and gene structure analysis results. The expression profile revealed SjCOMT11 and SjCOMT13 showed specific expression levels mainly in root. SjCOMT21, SjCOMT33 and SjCOMT37 were significantly expressed in the root and slightly expressed in the stem, bud and leaf. SjCOMT15 and SjCOMT45 were not only significantly expressed in root, but also expressed highly in leaf. Significantly enhanced expression of SjCOMT11, SjCOMT13, SjCOMT15, SjCOMT21, SjCOMT33, SjCOMT37, and SjCOMT45 suggested these OMTs are essential for cepharanthine synthesis in the S. japonica roots. Cis-acting element analysis revealed the potential roles of OMTs in S. japonica in growth, development, and resistance to stress. These findings provide insight into understanding the functions and characterization of OMTs from S. japonica and lay a foundation for further revealing the role of the OMT genes in the biosynthesis of cepharanthine.