Modular organization analysis of specific naringin/neoeriocitrin related gene expression induced by UVC irradiation in Drynaria roosii

Drynaria roosii is a traditional medicinal fern, whose rhizome is particularly valued for its effective flavonoid components of naringin/neoeriocitrin. UV irradiation can induce flavonoid accumulation in plants, however the molecular mechanism of UVC-mediated naringin/neoeriocitrin synthesis in D. roosii has never been reported. Our HPLC-tandem mass spectrometry (MS/MS) results showed that UVC irradiation increased naringin/neoeriocitrin contents (NNCs) based on irradiation dosage in D. roosii. According to the NGS data, DEG-based heat map analysis revealed up-regulation of naringin/neoeriocitrin synthetic genes was more obvious in 12h UVC irradiation (UV dose = 81.648 kJ m−2) when compared with 24h (UV dose = 163.296 kJ m−2), especially for PAL, C3'H and HCT in old rhizomes. Through systems biology method of modular organization analysis, we clustered 15,678 DEGs into 19 modules, and calculated correlation coefficients between modules and samples, as well as modules and NNCs. Four significant naringin-related modules were achieved and displayed high correlations with specific samples. Moreover, weighted gene co-expression network analysis results discovered that 4CL, CHS and HCT, C3H acted as the hub responsive genes to UVC irradiation involved in naringin and neoeriocitrin synthesis respectively, and presented high co-expression with MYB/bHLH-regulated DEGs. Overall, we demonstrated that UVC irradiation up-regulated the naringin/neoeriocitrin related gene expression in separate new and old rhizomes to enhance NNCs in a dose-dependent manner. Hormetic UVC dose ranges improving NNCs in D. roosii were established for the first time. Our work also provided new insights into the study of secondary metabolites in medicinal plants.