A G6P1E isomerase of sugar metabolism is involved in the flower colors of Dianthus chinensis

Abstract

Dianthus chinensis L. is indigenous to northern China, Korea, Mongolia, Kazakhstan, and southeastern Russia. It is widely cultivated in urban landscapes. Its flower has a great variety of colors and color schemes. Sugars control and induce anthocyanin synthesis and accumulation in plants. In sugar metabolism, many enzymes are specific for their substrate’s α or β anomer. Gaining and characterizing genes involved in sugar metabolism and flower color will be beneficial in clarifying the role of sugar in the flower colors of D. chinensis. Glucose-6-phosphate-1-epimerase (G6P1E, EC 5.1.3.15) catalyzes the α or β change of glucose-6-phosphate at the branch point of glucose metabolism. DchG6P1E1 (MZ292712) was isolated in D. chinensis and characterized using the tobacco rattle virus (TRV)-based virus-induced gene silencing (VIGS) system. Its cDNA full length is 1401 bp, including an open reading frame of 918 bp. In the DchG6P1E1-silenced flowers, the reducing purple was observed, as well as the anthocyanin content, reducing sugar content, G6P1E activity, and DchG6P1E1 expression were significantly decreased. During the development of floral buds and among the three flower colors, the anthocyanin content, reduced sugar content, G6P1E activity, and DchG6P1E1 expression rose dramatically, with pigments increasing in the petals. Among the organs, the flowers had the highest anthocyanin contents and reducing sugar. The highest levels of G6P1E activity and DchG6P1E1 expression were in the roots. The anthocyanin content was positively related to the reducing sugar content at 0.05 levels by correlation analysis. In conclusion, DchG6P1E1 is a root-enriched gene associated with flower colors in D. chinensis.