Unraveling the Mechanism Underlying the Glycosylation and Methylation of Anthocyanins in Peach    

Abstract

Modification of anthocyanin plays an important role in increasing its stability in plants. Here, six anthocyanins were identified in peach (Prunus persica), and their structural diversity is attributed to glycosylation and methylation. Interestingly, peach is quite similar to the wild species Prunus ferganensis but differs from both Prunus davidiana and Prunus kansueasis in terms of anthocyanin composition in flowers. This indicates that peach is probably domesticated from P. ferganensis. Subsequently, genes responsible for both methylation and glycosylation of anthocyanins were identified, and their spatiotemporal expression results in different patterns of anthocyanin accumulation in flowers, leaves, and fruits. Two tandem-duplicated genes encoding flavonoid 3-O-glycosyltransferase (F3GT) in peach, PpUGT78A1 and PpUGT78A2, showed different activity toward anthocyanin, providing an example of divergent evolution of F3GT genes in plants. Two genes encoding anthocyanin O-methyltransferase (AOMT), PpAOMT1 and PpAOMT2, are expressed in leaves and flowers, but only PpAOMT2 is responsible for the O-methylation of anthocyanins at the 39 position in peach. In addition, our study reveals a novel branch of UGT78 genes in plants that lack the highly conserved intron 2 of the UGT gene family, with a great variation of the amino acid residue at position 22 of the plant secondary product glycosyltransferase box. Our results not only provide insights into the mechanisms underlying anthocyanin glycosylation and methylation in peach but will also aid in future attempts to manipulate flavonoid biosynthesis in peach as well as in other plants.

Advances in flavonoid glycosyltransferase research: integrating recent findings with long-term citrus studies

“…In the glucose containing structures, the last two residues of the PSPG box (x and y) interact with the sugar, and are strongly conserved across all the enzymes. The terminal PSPG box residue (y) has been suggested as being indicative of sugar usage with glutamine associated with glucose activity and histidine with galactose activity (Kubo et al 2004;Cheng et al 2014). Although mutagenesis from histidine to glutamine in a S. baicalensis galactosytransferase was able to convey glucosyltransferase activity, the complementary mutation was not able to impart galactosyltransferase activity to a glucosyltransferase.…”

Genome-Wide Identification, Expression Patterns, and Functional Analysis of UDP Glycosyltransferase Family in Peach (Prunus persica L. Batsch)

“…Recently, UGT genes were likely to be responsible for glycosylation of anthocyanins in peach flowers (Cheng et al, 2014). This observation prompts us to further explore and characterize the potential functions of peach UGTs .…”

Biochemical and functional characterization of AcUFGT3a, a galactosyltransferase involved in anthocyanin biosynthesis in the red‐fleshed kiwifruit (Actinidia chinensis)

“…Many regulation genes involved in anthocyanin biosynthesis have been identified in fruits such as peach (Tuan et al , Zhou et al ), grape (Kobayashi et al , Deluc et al , Hichri et al , Matus et al , Perez‐Diaz et al ), apple (An et al , Chagne et al ), pear (Wang et al , Zhai et al ), litchi (Lai et al , Lai et al ) and Myrica rubra (Liu et al , Huang et al ). However, few studies have reported on the functional characterization of the structural gene families in fruiting plants (Gonzalez et al , Cheng et al , Li et al ).…”

“…The genes encoding UFGTs in a range of species can be divided into two groups, based on their specificity for sugar acceptors. The first group is responsible for attaching a sugar to anthocyanin aglycones, including anthocyanidin 3‐ O ‐glycosyltransferase (Fedoroff et al , Tohge et al , Gonzalez et al , Zhao et al , Cheng et al , Li et al , Sun et al ) and anthocyanidin 5,3‐ O ‐glucosyltransferase (Ogata et al ). The second group is responsible for further glycosylation of anthocyanidin 3‐ O ‐glycosides, leading to the formation of diglycoside and these have been reported in petunia (Kroon et al ), Japanese morning glory (Morita et al ), daisy (Sawada et al ) and Arabidopsis thaliana (Yonekura‐Sakakibara et al ).…”