Transcriptomic and physiological analysis reveals the accumulation mechanism of anthocyanin and apigenin in purple celery (Apium graveolens L.)

Purple celery, belonging to the Apiaceae family, represents a novel type of celery species known for its abundant pigmentation and valuable nutritional and aesthetic properties. Nevertheless, the process behind the color development in purple celery remains unexplored, impeding the utilization and enhancement of its genetic assets. Here, by measuring the contents of total flavonoids, total carotenoids, and anthocyanin during the three development stages, we found that with the growth and development of purple celery, the accumulation of anthocyanin in the epidermal cells of the petiole promoted the red coloration. Meanwhile, we observed a trend of initial increase followed by a decrease in apigenin levels. Through transcriptomic database construction, GSEA and pathway analysis, we identified numerous candidate genes related to the biosynthesis of anthocyanin and apigenin, while AgFNS1 and AgFNS2 controlled a greater diversion of naringenin from the apigenin pathway to the anthocyanin pathway. Additionally, WGCNA and interaction network analysis showed that bHLH, AP2/ERF, MYB, and WRKY transcription factor families mainly participated in the co-regulatory mechanism of anthocyanin and apigenin. This research aims to elucidate the color formation process of purple celery and lay the groundwork for leveraging celery germplasm innovation.