title: Different biosynthesis patterns among flavonoid 3-glycosides with distinct effects on accumulation of other flavonoid metabolites in pears (Pyrus bretschneideri Rehd.).
abstract: Flavonoid biosynthesis profile was clarified by fruit bagging and re-exposure treatments in the green Chinese pear 'Zaosu' (Pyrus bretschneideri Rehd.) and its red mutant 'Red Zaosu'. Two distinct biosynthesis patterns of flavonoid 3-glycosides were found in 'Zaosu' pear. By comparison with 'Red Zaosu', the biosynthesis of flavonoid 3-galactosides and flavonoid 3-arabinosides were inhibited by bagging and these compounds only re-accumulated to a small degree in the fruit peel of 'Zaosu' after the bags were removed. In contrast, the biosynthesis of flavonoid 3-gluctosides and flavonoid 3-rutinosides was reduced by bagging and then increased when the fruits were re-exposed to sunlight. A combination of correlation, multicollinearity test and partial-correlation analyses among major flavonoid metabolites indicated that biosynthesis of each phenolic compound was independent in 'Zaosu' pear, except for the positive correlation between flavonoid 3-rutincosides and flavanols. In contrast with the green pear cultivar, almost all phenolic compounds in the red mutant had similar biosynthesis patterns except for arbutin. However, only the biosynthesis of flavonoid 3-galactosides was relatively independent and strongly affected the synthesis of the other phenolic compounds. Therefore, we propose a hypothesis that the strong accumulation of flavonoid 3-galactosides stimulated the biosynthesis of other flavonoid compounds in the red mutant and, therefore, caused systemic variation of flavonoid biosynthesis profiles between 'Zaosu' and its red mutant. This hypothesis had been further demonstrated by the enzyme activity of UFGT, and transcript levels of flavonoid biosynthetic genes and been well tested by a stepwise linear regression forecasting model. The gene that encodes flavonoid 3-galacosyltransferase was also identified and isolated from the pear genome.
authors.affiliation: College of Horticulture, Northwest A&F University, Yangling, Shaanxi, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Zhai
authors.affiliation: College of Horticulture, Northwest A&F University, Yangling, Shaanxi, China.
authors.forename: Xiao-Ting
authors.initials: XT
authors.lastname: Liu
authors.affiliation: College of Horticulture, Northwest A&F University, Yangling, Shaanxi, China.
authors.forename: Wen-Ting
authors.initials: WT
authors.lastname: Feng
authors.affiliation: College of Horticulture, Northwest A&F University, Yangling, Shaanxi, China.
authors.forename: Sha-Sha
authors.initials: SS
authors.lastname: Chen
authors.affiliation: College of Horticulture, Northwest A&F University, Yangling, Shaanxi, China.
authors.forename: Ling-Fei
authors.initials: LF
authors.lastname: Xu
authors.affiliation: College of Horticulture, Northwest A&F University, Yangling, Shaanxi, China.
authors.forename: Zhi-Gang
authors.initials: ZG
authors.lastname: Wang
authors.affiliation: College of Horticulture, Northwest A&F University, Yangling, Shaanxi, China.
authors.forename: Jiang-Li
authors.initials: JL
authors.lastname: Zhang
authors.affiliation: College of Horticulture, Northwest A&F University, Yangling, Shaanxi, China.
authors.forename: Peng-Min
authors.initials: PM
authors.lastname: Li
authors.affiliation: College of Horticulture, Northwest A&F University, Yangling, Shaanxi, China.
authors.forename: Feng-Wang
authors.initials: FW
authors.lastname: Ma
mesh_terms: D000872:Anthocyanins / Q000378:metabolism; D005419:Flavonoids / Q000378:metabolism*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D006027:Glycosides / Q000096:biosynthesis*; D016695:Glycosyltransferases / Q000235:genetics; D053858:Metabolic Networks and Pathways; D010636:Phenols / Q000378:metabolism; D010641:Phenotype; D010802:Phylogeny; D010858:Pigmentation; D031989:Pyrus / Q000145:classification / Q000235:genetics / Q000378:metabolism*
chemical_list: D000872:Anthocyanins; D005419:Flavonoids; D006027:Glycosides; D010636:Phenols; D016695:Glycosyltransferases