| Abstrakt: |
Main conclusion: Two glycosyltransferase genes belonging to UGT88 family were identified to have 6ʹ-deoxychalcone 4ʹ-glucosyltransferase activity in dahlia. 6ʹ-Deoxychalcones (isoliquiritigenin and butein) are important pigments for yellow and orange to red flower color. 6ʹ-Deoxychalcones are glucosylated at the 4ʹ-position in vivo, but the genes encoding 6ʹ-deoxychalcone 4ʹ-glucosyltransferase have not yet been identified. In our previous study, it was indicated that snapdragon (Antirrhinum majus) chalcone 4ʹ-O-glucosyltransferase (Am4ʹCGT) has isoliquiritigenin 4ʹ-glucosylation activity. Therefore, to identify genes encoding 6ʹ-deoxychalcone 4ʹ-glucosyltransferase in dahlia (Dahlia variabilis), genes expressed in ray florets that shared high homology with Am4ʹCGT were explored. As a result, c34671_g1_i1 and c35662_g1_i1 were selected as candidate genes for 6ʹ-deoxychalcone 4ʹ-glucosyltransferases in dahlia. We conducted transient co-overexpression of three genes (c34671_g1_i1 or c35662_g1_i1, dahlia aldo-keto reductase1 (DvAKR1) or soybean (Glycine max) chalcone reductase5 (GmCHR5), and chili pepper (Capsicum annuum) MYB transcription factor (CaMYBA)) in Nicotiana benthamiana by agroinfiltration. Transient overexpression of c34671_g1_i1, DvAKR1, and CaMYBA resulted in increase in the accumulation of isoliquiritigenin 4ʹ-glucosides, isoliquiritigenin 4ʹ-O-glucoside, and isoliquiritigenin 4ʹ-O-[6-O-(malonyl)-glucoside]. However, transient overexpression of c35662_g1_i1, DvAKR1, and CaMYBA did not increase accumulation of isoliquiritigenin 4ʹ-glucosides. Using GmCHR5 instead of DvAKR1 showed similar results suggesting that c34671_g1_i1 has isoliquiritigenin 4ʹ-glucosyltransferase activity. In addition, we conducted co-overexpression of four genes (c34671_g1_i1, c35662_g1_i1 or Am4ʹCGT, DvAKR1 or GmCHR5, CaMYBA, and chalcone 3-hydroxylase from dahlia). Accumulation of butein 4ʹ-O-glucoside and butein 4ʹ-O-[6-O-(malonyl)-glucoside] was detected for c35662_g1_i1, suggesting that c35662_g1_i1 has butein 4ʹ-glucosyltransferase activity. Recombinant enzyme analysis also supported butein 4ʹ-glucosyltransferases activity of c35662_g1_i1. Therefore, our results suggested that both c34671_g1_i1 and c35662_g1_i1 are 6ʹ-deoxychalcone 4ʹ-glucosyltransferases but with different substrate preference. [ABSTRACT FROM AUTHOR] |
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