Impact of activated charcoal on the progression of somatic embryogenesis in grape cells: Histological and transcriptomic perspectives

•AC improves the consistency and synchronization of somatic embryogenesis in grapes.•ROS-, starch, cell wall, and hormone-related genes are involved in SE development.•Appropriate ROS concentration is crucial to SE formation in grapes.•AC provides favorable conditions for smooth SE development. Somatic embryogenesis is a crucial genetic transformation method in plants. Despite numerous studies being conducted for acquiring embryogenic competence in plant cells, somatic embryo (SE) induction from embryogenic cells (ECs) has attracted relatively limited research attention. In grapes, somatic cell induction is impeded by unidentified inhibitors, which hinders the progression of globular embryo (GE) formation and subsequently embryo development. We found that addition of activated charcoal (AC) to the grape SE induction medium augmented the speed, consistency, and synchronization of embryogenesis. Cell samples cultured in the induction medium with and without AC were thoroughly evaluated through histological anatomy analysis, subcellular structure observation, and comparative transcriptomic analysis. The histological observation revealed the specific timeline of SE formation. An intermediate developmental state, referred to as the globular embryo precursor (PGE), was observed during the induction of GE formation from EC. Members of transcription factor families such as WRKY, MYB, MADS, AP2/ERF, HB-KNOX, HB-HD-ZIP, HB-WOX, NAC, and GRF were identified in the early and middle stages of GE formation. Additionally, we explored the key roles of reactive oxygen species (ROS)-, starch-, cell wall-, and hormone-related genes. The cell wall-related genes were highly enriched in differentially expressed gene sets. Several amyloplasts in EC disappeared, potentially because of hydrolysis, and numerous mitochondria were observed. In AC-added samples, starch was consumed more, and cellulose hydrolysis-related genes were downregulated, whereas cellulose synthesis-related genes had higher expression than AC-free samples. ROS response-related genes were induced when GE induction was initiated. When applied, an optimal concentration of external H2O2 promoted SE initiation in grapes, whereas a high concentration caused delayed GE formation. This study suggests that, by absorbing and releasing substances, the added AC can create a stable buffer environment for cell survival, protect against excessive ROS- or inhibitor-induced cell damage, and support uninterrupted progress of som