Transcription and Metabolic Profiling Analysis of Three Discolorations in a Day of Hibiscus mutabilis.

In this study, we used combined transcriptomics and metabolomics to analyze the H. mutabilis cultivar's genetic and physiological mechanisms during three flower color transition periods (from white to pink, then from pink to red) within the span of one day. As a result, 186 genes were found to be significantly increased with the deepening of the H. mutabilis flower color; these genes were mainly involved in the expression of peroxidase 30, zinc finger protein, phosphate transporter PHO1, etc. In contrast, 298 genes were significantly downregulated with the deepening of H. mutabilis flower color, including those involved in the expression of probable O-methyltransferase 3, copper binding protein 9, and heat stress transcription factor A-6b. Some genes showed differential expression strategies as the flower color gradually darkened. We further detected 19 metabolites that gradually increased with the deepening of the H. mutabilis flower color, including L-isoleucine, palmitic acid, L-methionine, and (+)-7-isonitrobenzene. The content of the metabolite hexadecanedioate decreased with the deepening of the H. mutabilis flower color. Combined transcriptomics and metabolomics revealed that the metabolic pathways, including those related to anthocyanin biosynthesis, cysteine and methionine metabolism, and sulfur metabolism, appear to be closely related to H. mutabilis flower color transition. This study served as the first report on the genetic and physiological mechanisms of short-term H. mutabilis flower color transition and will promote the molecular breeding of ornamental cultivars of H. mutabilis.