DNA damage repair and ROS manipulation in response to 60Co γ-ray radiation and FcMYB5-mediated flavonoid response mechanisms in axillary buds of Ficus carica L

Abstract

Abstract Background The irradiation of plant species has been used to induce inheritable genetic variations in cropgermplasms. However, the underlying mechanisms involved remain unclear. In the present study, young shoot cuttings of Ficus carica L. were treated with 100 grays (Gy) of 60Co γ-rays and axillary buds were collected at 3, 6, 12, 24, 48 h post-irradiation. Results RNA-seq analysis revealed 5337, 7135, 4289, 1595 and 2356 differentially expressed genes (DEGs) at five time points, respectively. KEGG enrichment revealed the homologous recombination pathway displayed significant differential regulation at 3 and 6 h after irradiation, while pathways for DNA replication, base excision repair and mismatch repair were only significantly enriched at 3 h. taking together the number of 16 retrotransposons found upregulation at 6 h. The results indicated the major routes of early DNA damage repair and the window time of mutation initiation. DEGs of MAPK signaling pathway were significantly enriched at 6, 12, 24 and 48 h after irradiation demonstrated the mobilization of kinase signaling cascades in response to cellular stress. The SOD, POD and CAT enzyme activities of fig axillary buds after radiation treatment showed a decreasing and then increasing trend with increasing time, while the MDA and H2O2 contents basically maintained an increasing trend. Enriched DEGs in reactive oxygen species (ROS) scavenging, glutathione-S-transferase and of biosynthetic pathways for phenylpropanoids and flavonoids were detected at all time points, indicating a comprehensive mechanism for eliminating the radiation-induced cellular ROS burst. Among them, a large number of changes in MYB, WARKY and bHLH transcription factor family genes were found within 6 h. of radiation. Luciferase assay and yeast one-hybrid screen revealed that FcMYB5 binds the promoter region of FcCHS in the flavonoid biosynthesis pathway, suggesting that radiation may promote the functional activation of some transcription factors leading to the accumulation of antioxidant-like secondary metabolites. Conclusions Our results could help to improve the efficiency of radiation induced mutagenesis, support new traits creation and enable a better understanding of the mechanisms underlying radiation tolerance in different plant materials.