Comparative Transcriptomic Analysis Provides Insights into PSK-α-Mediated Regulation of Diosgenin Biosynthesis in Trigonella foenum-graecum.

Diosgenin is an important steroidal sapogenin widely used for the industrial production of steroidal drugs. Phytosulfokine-α (PSK-α) is a sulfated pentapeptide hormone known to regulate plant growth, development, and stress responses. However, its role in the regulation of diosgenin biosynthesis remains unclear. Fenugreek seedlings were treated with PSK-α to investigate its effects on diosgenin biosynthesis through metabolite profiling and comparative transcriptomic analyses. PSK-α induced a dynamic response in diosgenin accumulation, characterized by an initial decrease during the early stage of treatment followed by a gradual increase, ultimately resulting in 61.4% and 72.1% increases in diosgenin accumulation after 10 days and 15 days, respectively, compared with the corresponding random pentapeptide control. Comparative transcriptomic analysis between PSK-α-treated seedlings and the corresponding controls at 5 and 15 days identified key genes or transcript isoforms involved in diosgenin biosynthesis, PSK signaling and MAPK signaling pathways. Meanwhile, five candidate genes involved in diosgenin biosynthesis and PSK signaling exhibited expression patterns consistent with the dynamic accumulation pattern of diosgenin. To further dissect the regulatory network, co-expression network analysis between these 28 candidate genes involved in diosgenin biosynthesis and PSK signaling and 1407 transcription factor-encoding genes identified candidate transcription factors potentially involved in the coordinated regulation of diosgenin biosynthesis and PSK signaling. This study suggests that PSK-α may contribute to enhanced diosgenin accumulation through coordinated transcriptional regulation of diosgenin biosynthesis and PSK signaling pathways, providing new insights into the regulation of plant secondary metabolism by peptide hormones.