Abstract
Wild-type petunia pollen accumulates high levels of flavonol 3-O-glycosides. Pollen from conditionally male-fertile petunia has no flavonols and is unable to germinate. Pollen function is restored both in vivo and in vitro by providing flavonol aglycones, but not flavonol glycosides, to the pollen. In the present study, incubation of an in vitro suspension of conditionally male-fertile pollen with kaempferol or quercetin resulted in the accumulation of kaempferol and quercetin 3-O-glycosides in the pollen. We identified two glycosyltransferase activities associated with the intact pollen grain that catalyze the formation of a gametophyte-specific class of flavonol glycosides. Feeding studies showed that product formation was highly specific for flavonols with an unsubstituted 3-hydroxyl group and was not dependent on an external source of UDP-hexose. Ultraviolet spectral analysis, fast atom bombardment mass spectrometry, 1H-nuclear magnetic resonance, and 13C-nuclear magnetic resonance identified the products as kaempferol and quercetin 3-O-(2"- O-beta-D-glucopyranosyl)-beta-D-galactopyranoside, identical with the flavonol 3-O-glycosides present in wild-type pollen. The sugars are linked in a 1-->2 configuration that results in a pollen-specific class of compounds. To retain both glycosyltransferase activities in a cell-free extract, it was necessary to add triton X-100, suggesting that one or both of the proteins may be associated with a pollen membrane. A model for flavonol glycoside biosynthesis and uptake into the pollen is discussed in terms of the germination requirement for flavonols.
Full Text
The Full Text of this article is available as a PDF (1.4 MB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Bar-Peled M., Lewinsohn E., Fluhr R., Gressel J. UDP-rhamnose:flavanone-7-O-glucoside-2''-O-rhamnosyltransferase. Purification and characterization of an enzyme catalyzing the production of bitter compounds in citrus. J Biol Chem. 1991 Nov 5;266(31):20953–20959. [PubMed] [Google Scholar]
- Herdt E., Sütfeld R., Wiermann R. The occurrence of enzymes involved in phenylpropanoid metabolism in the tapetum fraction of anthers. Cytobiologie. 1978 Aug;17(2):433–441. [PubMed] [Google Scholar]
- Kroon J., Souer E., de Graaff A., Xue Y., Mol J., Koes R. Cloning and structural analysis of the anthocyanin pigmentation locus Rt of Petunia hybrida: characterization of insertion sequences in two mutant alleles. Plant J. 1994 Jan;5(1):69–80. doi: 10.1046/j.1365-313x.1994.5010069.x. [DOI] [PubMed] [Google Scholar]
- Mo Y., Nagel C., Taylor L. P. Biochemical complementation of chalcone synthase mutants defines a role for flavonols in functional pollen. Proc Natl Acad Sci U S A. 1992 Aug 1;89(15):7213–7217. doi: 10.1073/pnas.89.15.7213. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Pollak P. E., Vogt T., Mo Y., Taylor L. P. Chalcone Synthase and Flavonol Accumulation in Stigmas and Anthers of Petunia hybrida. Plant Physiol. 1993 Jul;102(3):925–932. doi: 10.1104/pp.102.3.925. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Schlupmann H., Bacic A., Read S. M. Uridine Diphosphate Glucose Metabolism and Callose Synthesis in Cultured Pollen Tubes of Nicotiana alata Link et Otto. Plant Physiol. 1994 Jun;105(2):659–670. doi: 10.1104/pp.105.2.659. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Vogt T., Pollak P., Tarlyn N., Taylor L. P. Pollination- or Wound-Induced Kaempferol Accumulation in Petunia Stigmas Enhances Seed Production. Plant Cell. 1994 Jan;6(1):11–23. doi: 10.1105/tpc.6.1.11. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ylstra B., Touraev A., Moreno R. M., Stöger E., van Tunen A. J., Vicente O., Mol J. N., Heberle-Bors E. Flavonols stimulate development, germination, and tube growth of tobacco pollen. Plant Physiol. 1992 Oct;100(2):902–907. doi: 10.1104/pp.100.2.902. [DOI] [PMC free article] [PubMed] [Google Scholar]