Cloning And Biochemical Characterization Of UDP-rhamnose Biosynthesis Genes From Morella Rubra And Prunus Persica

UDP-rhamnose(UDP-Rha)is an important sugar donor for plant glycoside derivatives and participates in the formation of various rhamnosides.Rhamnoside is widely present in different tissues of plants and has important biological activities.However,commercialized UDP-Rha is difficult to obtain,which limits the biological research related to plant rhamnosides.In this study,Chinese bayberry(Morella rubra)and peach(Prunus persica)were used as research materials.The types of flavonol rhamnosides were identified,and the genes for UDP-Rha synthesis were cloned,and their biochemical functions were analyzed.The main results are as follows:1.Three flavonol rhamnosides were detected in different tissues of Chinese bayberry by HPLC,including myricetin-3-O-rhamnoside(M3Rha),quercetin-3-O-rhamnoside(Q3Rha)and kaempferol-3-O-rhamnoside(K3Rha).Four flavonol rhamnosides were detected in different tissues of peach,including quercetin-3-O-rutinoside(Q3Rut),kaempferol-3-O-rutinoside(K3Rut),isorhamnetin-3-Orutinoside(I3Rut)and K3 Rha.2.Two genes for UDP-Rha synthase,named MrRHM1 and MrNRS/ER,were cloned from Chinese bayberry,which containted full-length cDNAs with 2016 bp and 909 bp,respectively.The amino acid sequence of MrNRS/ER is highly similar to the C-terminal sequence of MrRHM1.MrRHM1 can catalyze UDP-glucose(UDP-Glc)to UDP-Rha,and the optimum pH is 9.0,and the optimum temperature is 25℃.MrNRS/ER cannot catalyze the formation of UDP-Rha by UDP-Glc independently,while it can work together with N-terminal of AtRHM2(AtRHM2-N)to convert UDP-Glc to UDP-Rha.3.Two genes for UDP-Rha synthase,named PpRHM1 and PpRHM2,were cloned from peach,which containted full-length cDNAs with 2028 bp and 2016 bp,respectively.The amino acid sequence similarity of PpRHM1 and PpRHM2 is 84.47%.PpRHM1 and PpRHM2 can catalyze UDP-Glc to UDP-Rha.The optimum pH is 9.0 and 8.5,respectively,and the optimum temperature is 35℃ and 30℃,respectively.The results of this study indicate that MrRHM1,PpRHM1 and PpRHM2 can catalyze UDP-Glc to produce UDP-Rha,which is of great significance for the following research of plant rhamnose-related glycoside biosynthesis and regulation.