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Metabolic Characterization of the Anthocyanidin Reductase Pathway Involved in the Biosynthesis of Flavan-3-ols in Elite Shuchazao Tea (Camellia sinensis) Cultivar in the Field

by Lei Zhao 1,2,†, Xiao-Lan Jiang 1,†, Yu-Mei Qian 1, Pei-Qiang Wang 1, De-Yu Xie 1,3,*, Li-Ping Gao 4,* and Tao Xia 1,*
1
State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, 130 West Changjiang Rd., Hefei 230036, China
2
College of Horticulture, Qingdao Key Laboratory of Genetic Improvement and Breeding in Horticultural Plants, Qingdao Agricultural University, 700 Changcheng Rd., Qingdao 266109, China
3
Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC 27695, USA
4
School of Life Science, Anhui Agricultural University, 130 West Changjiang Rd., Hefei 230036, China
*
Authors to whom correspondence should be addressed.
These authors contributed equally to this work.
Molecules 2017, 22(12), 2241; https://doi.org/10.3390/molecules22122241
Received: 15 November 2017 / Revised: 11 December 2017 / Accepted: 12 December 2017 / Published: 15 December 2017
Anthocyanidin reductase (ANR) is a key enzyme in the ANR biosynthetic pathway of flavan-3-ols and proanthocyanidins (PAs) in plants. Herein, we report characterization of the ANR pathway of flavan-3-ols in Shuchazao tea (Camellia sinesis), which is an elite and widely grown cultivar in China and is rich in flavan-3-ols providing with high nutritional value to human health. In our study, metabolic profiling was preformed to identify two conjugates and four aglycones of flavan-3-ols: (−)-epigallocatechin-gallate [(−)-EGCG], (−)-epicatechin-gallate [(−)-ECG], (−)-epigallocatechin [(−)-EGC], (−)-epicatechin [(−)-EC], (+)-catechin [(+)-Ca], and (+)-gallocatechin [(+)-GC], of which (−)-EGCG, (−)-ECG, (−)-EGC, and (−)-EC accounted for 70–85% of total flavan-3-ols in different tissues. Crude ANR enzyme was extracted from young leaves. Enzymatic assays showed that crude ANR extracts catalyzed cyanidin and delphinidin to (−)-EC and (−)-Ca and (−)-EGC and (−)-GC, respectively, in which (−)-EC and (−)-EGC were major products. Moreover, two ANR cDNAs were cloned from leaves, namely CssANRa and CssANRb. His-Tag fused recombinant CssANRa and CssANRb converted cyanidin and delphinidin to (−)-EC and (−)-Ca and (−)-EGC and (−)-GC, respectively. In addition, (+)-EC was observed from the catalysis of recombinant CssANRa and CssANRb. Further overexpression of the two genes in tobacco led to the formation of PAs in flowers and the reduction of anthocyanins. Taken together, these data indicate that the majority of leaf flavan-3-ols in Shuchazao’s leaves were produced from the ANR pathway. View Full-Text
Keywords: anthocyanidin reductase; (+)-catechin; (−)-epicatechin; (−)-epicatechin-gallate; (−)-epigallocatechin; (−)-epigallocatechin-gallate; (+)-gallocatechin anthocyanidin reductase; (+)-catechin; (−)-epicatechin; (−)-epicatechin-gallate; (−)-epigallocatechin; (−)-epigallocatechin-gallate; (+)-gallocatechin
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MDPI and ACS Style

Zhao, L.; Jiang, X.-L.; Qian, Y.-M.; Wang, P.-Q.; Xie, D.-Y.; Gao, L.-P.; Xia, T. Metabolic Characterization of the Anthocyanidin Reductase Pathway Involved in the Biosynthesis of Flavan-3-ols in Elite Shuchazao Tea (Camellia sinensis) Cultivar in the Field. Molecules 2017, 22, 2241.

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