Heterologous Expression and Characterization of Putative Secondary Product Glucosyltransferase (PGT)Clones 4 and 11 Isolated from Citrus paradisi

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Plant secondary products such as flavonoids have a variety of roles in plants including UV protection, antifeedant activity, pollinator attraction, stress response, flavor, and many more. These compounds also have effects on human physiology. Glucosylation is an important modification of many flavonoids and other plant secondary products. In grapefruit, glucosylation is important in the synthesis of the bitter compound naringin and several flavonoid glucosyltransferase (GT) enzymes have been characterized from young grapefruit leaf tissue. To study structure and function of flavonoid GTs, it is necessary to isolate cDNA’s that can be cloned and manipulated. In prior work, the plant secondary product glucosyltransferase (PSPG) box was used to identify putative GT clones. We report on results from experiments to test the hypothesis that PGT clones 4 and 11 are plant secondary product GTs, specifically flavonoid GTs. Previously, PGT 4 was cloned into a bacterial expression system, however all protein was localized into inclusion bodies and GT activity could not be tested. For this work, recombinant PGT 4 and PGT 11 were transformed into yeast and the proteins expressed and screened for glucosyltransferase activity with a variety of flavonoid substrates including flavanones, flavones, and flavonols.


Corvallis, OR

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