Molecular Mechanism Of Apple MdMYB25 Gene Regulating Anthocyanin Synthesis Induced By Visible Light And UV-B

As a common secondary metabolite,anthocyanins can play an important role in human health and resistance to certain diseases.The pigmentation of apple peel mainly comes from the accumulation of anthocyanins.Under the influence of a variety of biotic and abiotic factors,the upstream and downstream genes anthocyanin-related genes of apples jointly regulate the synthesis of anthocyanins.MYB is most extensively studied as part of the MBW complex,but functional studies of the MdMYB25 gene in apples have not been reported.In this experiment,the MdMYB25 gene was cloned from apple peel,and an overexpression vector was constructed for subsequent experiments.The results are as follows:(1)Apple MdMYB25 was cloned.The full length of the gene is 762 bp,encoding 253 amino acids,the molecular weight of the protein is 29.03 k Da,and the isoelectric point is 7.59.Through the comparison of multiple pairs of amino acid sequences,it was found that there was a R2R3 functional domain in the amino acid sequence of MdMYB25.(2)The results of tissue expression assay experiments,showed that MdMYB25 was highly expressed in peel and flesh.Affected by the action site of the promoter,MdMYB25 can be induced by methyl jasmonate,gibberellin and abscisic acid.The results of abiotic stress analysis showed that MdMYB25 was significantly expressed under low temperature stress.MdMYB25 does not have transcriptional self-activating activity.(3)MdMYB25 was transiently expressed and silenced in apple peel,and treated with visible light and UV-B.It was found that there was obvious accumulation of anthocyanin in the overexpressed region of the peel gene.The results of antioxidant enzyme activity assay showed that the antioxidant capacity of the overexpressed region was improved.Anthocyanin synthesis was inhibited in the gene silenced region of fruit peel.When overexpressing MdMYB25 in apple callus,the same obvious accumulation of anthocyanins can be observed,and the overexpression callus under 16 ℃ treatment has more anthocyanin accumulation than that under normal temperature treatment.Therefore,we speculate that the MdMYB25 gene is involved in the regulation of anthocyanin synthesis in apple peel.(4)LUC experiments and yeast one-hybrid proved that the c DNA region of MdMYB25 can combine with the promoter regions of MdANS and MdUFGT,and have an interactive relationship.Yeast two-hybrid experiments proved that MdMYB25 can interact with MdHY5,but not with MdUVR8.MdUVR8 interacts with MdHY5 and indirectly regulates MdMYB25.Therefore,we infer that the upstream MdHY5 and MdUVR8 act on MdMYB25,and MdMYB25 promotes the synthesis of anthocyanins in apple peel by regulating the transcription of downstream MdANS and MdUFGT.