The Correlation Between Anthocyanidin Accumulation And Activities Of Enzymes Involved In Anthocyanidin Biosynthesis In Puple-fleshed Sweetpotato [Ipomoea Batatas (L.)Lam.]

Purple-fleshed sweet potato [Ipomoea batatas (L.)Lam.] is an excellent new type of sweet potato cultivar which was focused as an important source of natural anthocyanin pigment in the world. Anthocyanin has a variety of medincnal functions such as preventing oxidation and aging, scavenging the free radical, Antimutagenic as well as preventing and curing angiocardiopathy. Many important enzymes are involved in the biosynthesis and accumulation of anthocyanin, such as phenylalanine ammonialyase (PAL), chalcone synthase (CHS), dihydroflavonol 4-reductase (DFR) and UDP-glucose flavonoid-3-oxyglucosy transferase (UF3GT). However, there are some different dissensions about whether those enzymes are the key enzymes of the biosynthetic pathway of anthocyanin or not in different plants.In this paper, four purple-fleshed sweet potato strains'A1','A3','A5', 'Yamakawamurasaki'and one white-fleshed sweet potato strain'Yubeibai'were used as experiment materials. In order to determine the key enzymes and the site of the biosynthesis of anthocyanin in different strains of purple-fleshed sweet potato, the correlation among the contents of anthocyanin, PAL activities and DFR activities were annlyzed. First of all, the contents of anthocyanin and the enzyme activities of phenylalanine ammonialyase and dihyoflavonol 4-reductase in different organs of three different strains in the same growth period, including two purple-fleshed sweet potato strains 'A3','Yamakawamurasaki'and one white-fleshed sweet potato strain 'Yubeibai' were determined. The relations between the content of anthocyanin and the PAL activity and the relations between the content of anthocyanin and the DFR activity were investigated by correlation analysis and the linear regression models were established. Subsequently, the contents of anthocyanin and the enzyme activities of phenylalanine ammonialyase and dihyoflavonol 4-reductase in different organs of five different sweet potato strains in five different growth stages were determined. The relations between the content of anthocyanin and the PAL activity and the relations between the content of anthocyanin and the DFR activity were also investigated by correlation analysis and establishing the linear regression models.This research aimed to reinforce the theoretical foundation for the exploitation and molecular breeding of purple-fleshed sweetpotato. Main works and results were listed as follows:1. In the same growth period, no matter in different organs of the same strain or the whole plant of different strains, purple-fleshed sweetpotato anthocyanin content showed significant differences, this suggested that the accumulation of anthocyanin in purple-fleshed sweetpotato is space-specific.2. In different growth stages, purple-fleshed sweetpotato anthocyanin content showed significant differences in each organ of the same strain, this suggested that anthocyanin accumulation in purple-fleshed sweetpotato is time-specific.3. In the same growth period, no matter in different organs of the same strain or the whole plant of different sweetpotato strains, the activities of PAL and DFR both showed significant differences, which means that the activities of PAL and DFR are space-specific in purple-fleshed sweetpotato.4. In different growth stages, the activities of PAL and DFR also showed significant differences both in each organ of the same strain, which means that the activities of PAL and DFR are time-specific in purple-fleshed sweetpotato.5. The activities of PAL and DFR are dramatically and positively correlated with the content of anthocyanin no matter in different organs of the same strain or in same organ of the same strain in different growth stages. The results indicated that the activities of PAL and DFR were consistent with the content of anthocyanin both in space and time and there was no transportation in the process of the biosynthesis of anthocyanin in purple-fleshed sweet potato. Namely, the biosynthesis of anthocyanin is in situ synthesis.6. Phenylalanine ammonialyase and dihyoflavonol 4-reductase are both key enzymes of the biosynthetic pathway of anthocyanin in purple-fleshed sweet potato.7. The impact of DFR is greater than that of PAL in the biosynthesis and accumulation of anthocyanin in purple-fleshed sweet potato.