Transcriptome sequencing and anthocyanin metabolite analysis involved in leaf red color formation of Cinnamomum camphora

Cinnamomum camphora, a key multifunctional tree species, primarily serves in landscaping. Leaf color is crucial for its ornamental appeal, undergoing a transformation to red that enhances the ornamental value of C. camphora. However, the molecular mechanisms underlying this transformation remain largely unexplored. In this study, green leaf (GL), color turning red leaf (RL) and whole red leaf (WRL) were obtained to measure pigment contents, while GL and RL were analyzed for transcriptomic alterations. A decline in chlorophyll content and a rise in anthocyanins were observed during the transition from green to red leaves. Using LC MS/MS, 11 types of anthocyanins showed significant accumulative differences, with cyanidin-3,5-O-diglucoside exhibiting the greatest disparity. Comparative RNA-seq identified 22,948 genes against reference genes, revealing 544 novel genes. Of these, 3,222 genes were up-regulated and 7,391 genes were down-regulated when the FPKM mean value > 1 in at least one group. The ribosome was identified as the most abundant KEGG term, with a substantial number of down-regulated differentially expressed genes (DEGs). The results indicated a downward trend in protein content, with GL exhibiting the highest protein concentration. 22, 4, and 29 DEGs were associated with chlorophyll biosynthesis, chlorophyll degradation, and anthocyanin biosynthesis, respectively. Most DEGs related to chlorophyll biosynthesis were down-regulated. SGR and SGRL, which are associated with chlorophyll degradation, exhibited opposite differential expression, resulting in a significant decrease in chlorophyll content in RL. The significantly up-regulated genes ANS and UFGT are advantageous for anthocyanin biosynthesis, contributing to the red coloration observed. Additionally, differential expression was noted in 40 R2R3-MYBs. Two MYB90 (Ccam01G003512 and Ccam01G003515) homologs of AtMYB113 were also identified showed high levels of up-regulation in RL. These findings suggest a strong correlation between pigment metabolism and transcriptome data, elucidating the mechanism that leads to the red coloration of leaves in C. camphora.