Reciprocal regulation ofArabidopsis UGT78D2 and BANYULS is critical for regulation of the metabolic flux of anthocyanidins to condensed tannins in developing seed coats |
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Authors: | Yeon Lee Hye Ryon Yoon Yong Sook Paik Jang Ryul Liu Won-il Chung Giltsu Choi |
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Institution: | (1) Department of Biological Sciences, KAIST, 305-701 Daejeon, Korea;(2) Department of Chemistry, Kyung Hee University, 449-701 Suwon, Korea;(3) Korea Research Institute of Bioscience and Biotechnology, 305-333 Daejeon, Korea |
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Abstract: | Anthocyanins are major color pigments in plants. Their biosynthetic pathways are well established, and the majority of these
biosynthetic enzymes have been identified in model plants such asArabidopsis, maize, and petunia. One exception inArabidopsis is UDP-glucose:flavonoid 3-O-glucosyltransferase (UF3GT). This enzyme is known as Bronze-1 (Bz1 ) in maize, where it converts
anthocyanidins to anthocyanins. Phylogenetic sequence analysis of theArabidopsis thaliana UDP-glycosyltransferase (UGT) family previously indicated that UGT78D1, UGT78D2, and UGT78D3 cluster together with UF3GTs
from other species. Here, we report thatUGT78D2 encodes a cytosolic UGT that is functionally consistent with maize Bz-1. Biochemically, UGT78D2 catalyzes the glucosylation
of both flavonols and anthocyanidins at the 3-OH position. A T-DNA-insertedugt78d2 mutant accumulates very little anthocyanin and lacks 3-O-glucosylated quercetin. Expression analysis indicated thatUGT78D2, in opposite toBANYULS, is highly expressed in anthocyanin-accumulating seedlings but repressed in condensed tannin-accumulating seed coats. This
suggests that the reciprocal regulation of these two genes is important in directing the metabolic flux to either anthocyanins
or condensed tannins. Consistent with this, the ectopic expression of UGT78D2 produces purple-colored seed coats due to the
accumulation of anthocyanins. Taken together, our data indicate thatUGT78D2 encodes an enzyme equivalent to maize Bz1, and that the reciprocal regulation of UGT78D2 and BANYULS is critical for the
regulation of metabolic flux of anthocyanidins inArabidopsis. |
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Keywords: | anthocyanin Arabidopsis flavonoid metabolic flux UF3GT UCT78D2 |
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