Ethylene-induced rapid anthocyanin degradation in Vanda 'Sansai Blue' orchid cut flowers: Coordinated regulation of biosynthetic genes and class III peroxidases revealed by transcriptome analysis

Ethylene is a key regulator of postharvest senescence and quality deterioration in many ornamental crops, yet the molecular mechanisms underlying ethylene-induced petal discoloration remain poorly understood in orchids. In Vanda ‘Sansai Blue’ cut flowers, exposure to exogenous ethylene rapidly accelerates petal discoloration accompanied by anthocyanin loss. This study aimed to elucidate the genetic and molecular mechanisms regu­ lating ethylene-induced anthocyanin degradation. Cut florets were exposed for 24 h to either air (control) or to 10 µL L⁻¹ ethylene, and RNA-seq analysis was performed at three time points: prior to treatment, immediately after treatment, and 24 h post-treatment. Comparative transcriptome analysis between control flowers and ethylene-treated flowers identified differentially expressed genes (DEGs) associated with metabolism of various phytohormones, including ethylene, cytokinin, auxin and jasmonic acid signal transduction pathways. Ethylene treatment resulted in rapid downregulation of genes involved in phenylpropanoid and anthocyanin biosynthesis pathways. In contrast, several class III peroxidase (POD) genes were significantly upregulated. This response was accompanied by enhanced expression of ethylene signaling–related transcription factors (TFs), suggesting co­ ordinated regulation during the rapid discoloration process. These findings demonstrate that the ethyleneinduced petal discoloration in Vanda 'Sansai Blue' cut flowers involves coordinated downregulation of phenyl­ propanoid- and anthocyanin-related genes and TFs, accompanied by a simultaneous induction of POD genes, highlighting a complex regulatory network underlying this postharvest pigment degradation.