CircRNA-mediated ceRNA regulatory network during flower development and color formation in Melastoma candidum

Melastoma candidum D. Don is widely distributed in South China. However, its application in the garden industry is not ideal due to its sole flower color; thus, its color needs urgent improvement. In this study, we conducted high throughput transcriptome sequencing for circular RNA (circRNA), mRNA, small RNA (sRNA), and widely targeted metabolome in flowers at three developmental stages. RNA expression and metabolite abundance analyses identified differentially expressed circRNAs (DEcircRNAs), mRNAs (DEmRNAs), miRNAs (DEmiRNAs), and differentially synthesized metabolites (DSmets). Alternative variants of genes were given statistics and the reason for their occurrence was analyzed. GO enrichment and KEGG analyses were conducted on the source gene of DEcircRNAs and KEGG analyses on DSmets. Key genes and metabolites were identified in flavonoid, flavone, anthocyanin, carotenoid, and alkaloid biosynthetic pathways. Based on the above analyses, we built a circRNA-mediated ceRNA regulatory network. Nine circRNA-mediated ceRNA regulatory routines were obtained. Within the ceRNA regulatory network, circRNAs and mRNAs displayed positive correlations, both of which exhibit negative correlations with miRNAs, indicating their important roles during flower development and color formation of M. candidum. Amongst, circ_000434-miR5207-McF3H could regulate the biosynthesis of Dihydroquercetin, Dihydromyricetin, and Pinobanksin; circ_000302-miR319–5p-McHST and circ_00012 -miR826-McTAT could regulate the biosynthesis of p-Counmaryl shikimic acid. Our research explored the role of circRNAs in flower development and the color formation process and provided a theoretical foundation for flower color improvement in M. candidum.