Transcriptomics profiling and WGCNA provide new insights into anthocyanin metabolism in spring orchid (Cymbidium goeringii) flowers for future industrial applications

Given the rising demand for natural pigments and functional compounds, the flowers of spring orchid (Cymbidium goeringii), which are rich in bioactive anthocyanins, are a promising yet underutilized resource. Nevertheless, the metabolic regulatory mechanism that mediates the accumulation of anthocyanins in this species is still largely unknown. In this study, the physiological, comparative transcriptomics, and bioinformatics analyses were integrated to evaluate the total anthocyanin (TA) content and transcriptomic profiles of three floral tissues of the dark purple flowers from C. goeringii ‘Hei Ban’ (S: sepal, P: petal, and L: labellum) at three developmental stages (PB: bud stage, PH: half blooming stage, and PF: full blooming stage). The highest TA content in sepals was detected at PH [3.55 mg·g−1 fresh weight (FW)] and in petals at PB (3.65 mg·g−1 FW), highlighting their potential as a promising natural source for anthocyanin-based functional products. Subsequently, specific structural genes and transcription factors (TFs) potentially regulating flower color of C. goeringii were investigated based on the Weighted gene co-expression network analysis (WGCNA), including key structural genes [especially dihydroflavonol 4-reductase (DFR)] and TFs [MYB (myeloblastosis-related) and WRKY (WRKY domain-containing)]. During flower development, DFR (GL05021 and GL06597) expression levels were strongly positively correlated with MYB (GL08332) and WRKY (GL32178), which are the candidate genes potentially associated with anthocyanin accumulation. Further, the labellum color was potentially affected by carotenoid biosynthesis. These results provide valuable insights for the efficient utilization and value enhancement of spring orchid and other ornamental orchids in natural pigment extraction and functional products development.