RrGT1, a key gene associated with anthocyanin biosynthesis, was isolated from Rosa rugosa and identified via overexpression and VIGS.

At present, research on the flower color of Rosa rugosa requires very innovative and practical studies. Glycosylation plays an important role in increasing the stability and solubility of anthocyanins in plants. In this study, a gene with a full-length cDNA of 1161 bp encoding 386 amino acids, designated RrGT1 (MK034140), was isolated from the flowers of R. rugosa 'Zizhi' and then functionally characterized. Sequence alignment revealed that the coding regions of RrGT1 were highly specific among different species but still contained typical conserved amino acid residues that are crucial for RrGT1 enzyme activity. RrGT1 transcripts were detected in various tissues of R. rugosa 'Zizhi' and Rosa davurica, and their expression patterns corresponded with the accumulation of anthocyanins. Additionally, the in vivo function of RrGT1 was investigated via its overexpression in Arabidopsis thaliana. Transgenic Arabidopsis plants expressing RrGT1 regained red color pigmentation of their leaves and flower stems, indicating that RrGT1 could encode a functional glycosyltransferase (GT) protein for anthocyanin biosynthesis and could function in other species. The functional verification of RrGT1 for anthocyanin biosynthesis in R. rugosa was performed via virus-induced gene silencing (VIGS). This was the first time that a VIGS system was developed for use with perennial Rosa plants grown naturally in the field as experimental materials to study a key color-controlling gene in Rosa. When the RrGT1 gene was silenced, the Rosa plants displayed a pale petal color phenotype. The detection results showed that the expression of the endogenous RrGT1 gene was significantly downregulated while the six key structural genes in its upstream were normally expressed, and the contents of all anthocyanins also decreased significantly. Therefore, we speculated that glycosylation of RrGT1 plays a crucial role in anthocyanin biosynthesis in R. rugosa.