First identification of auxin glycosyltransferase MdUGT74BP1 from apple

Abstract The glycosylation modification of auxin is considered to be one of the important mechanisms for regulating the dynamic balance of plant active hormones in different tissue cells. It is closely related to maintaining the dynamic balance of auxin content in plants, plant growth and development, and environmental response. In this study, we successfully cloned a glycosyltransferase gene MdUGT74BP1 from an apple using molecular cloning technology. After constructing its prokaryotic expression vector, the active enzyme protein was purified and an in vitro enzymatic reaction revealed that MdUGT74BP1 may be a glycosylated growth element and its analogs. The overexpression of MdUGT74BP1 into Arabidopsis thaliana revealed that, compared to the wild-type, the MdUGT74BP1 -overexpressing line showed an auxin-deficient phenotype. After exogenously spraying auxin IBA, the free auxin and auxin sugar esters of each plant were extracted and tested by HPLC. Compared with mutant plants, the auxin sugar ester content in the overexpressed lines increased significantly, while the free auxin content decreased significantly. These results further illustrate that MdUGT74BP1 functions as glycosylated auxin in plants. We used qRT-PCR technology to detect the auxin pathway-related genes in each strain, revealing that the expression of the related genes was consistent with the phenotype. In conclusion, this study was the first to successfully identify glycosyltransferase MdUGT74BP1 from apples, providing a theoretical and practical basis for the development and utilization of apple germplasm resources.