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Identification of aHighly SpecificIsoflavone7-O-glucosyltransferase in the soybean(Glycine max(L.)Merr.) Ayuta FunakiToshiyuki WakiAkio Noguchi2015 год

Identification of a Highly Specific Isoflavone 7-O-glucosyltransferase in the soybean (Glycine max(L.) Merr.)
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Аннотация: Isoflavone conjugates [7-O-β-D-glucosides and 7-O-(6″-malonyl-β-D-glucosides) of daidzein and genistein] accumulate in soybean roots and serve as the stored precursors of isoflavones (aglycons), which play very important roles in the rhizobia-mediated nodulation of this plant. Thus far, the isoflavone 7-O-glucosyltransferase (GmIF7GT or GmUGT1) has been biochemically characterized and is believed to be involved in isoflavone conjugate biosynthesis. The soybean genome encodes many other glycosyltransferase homologs (GmUGTs) that are related to GmUGT1; however, their catalytic properties, substrate specificities, and role(s) in isoflavone conjugation are unknown. In this study, nine different GmUGT1-related GmUGT cDNAs were isolated; six of these cDNAs belonged to two distinct phylogenetic subgroups (A and B), and these six were functionally characterized. The results showed that GmUGT4, a representative of subgroup A, encoded a UGT that was highly specific for isoflavones showing kcat and kcat/Km values for daidzein of 5.89 ± 0.65 s−1 and 2.91 × 105 s−1M−1, respectively. Moreover, GmUGT4 was expressed in the roots (mainly in lateral roots) of the 7-day-old seedlings and seeds, both of which contained abundant amounts of isoflavone conjugates. By contrast, GmUGT1 and GmUGT7, which were subgroup B members, encoded enzymes with broad glucosyl-acceptor specificities and were mainly expressed in the aerial portions (cotyledons and hypocotyls) of the seedlings. In the present study, we proposed that the role of isoflavone glucosylation in a soybean plant is assigned to different GmUGT members in an organ/tissue-dependent manner. We also established the functional importance of GmUGT4 in the biosynthesis of isoflavone conjugates in lateral roots that make a major contribution to overall N2 fixation.
Год издания: 2015
Авторы: Ayuta Funaki, Toshiyuki Waki, Akio Noguchi, Yosuke Kawai, Satoshi Yamashita, Seiji Takahashi, Tôru Nakayama
Издательство: Oxford University Press
Источник: Plant and Cell Physiology
Ключевые слова: Legume Nitrogen Fixing Symbiosis, Soybean genetics and cultivation, Plant nutrient uptake and metabolism
Другие ссылки: Plant and Cell Physiology (PDF)
Plant and Cell Physiology (HTML)
PubMed (HTML)