PLANT PHYSIOLOGY , Vol 102, Issue 3 925-932, Copyright © 1993 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Chalcone Synthase and Flavonol Accumulation in Stigmas and Anthers of Petunia hybrida
P. E. Pollak, T. Vogt, Y. Mo and L. P. Taylor
Department of Horticulture and Program in Plant Physiology, Washington State University, Pullman, Washington 99164-6414
Flavonol aglycones are required for pollen germination in petunia (Petunia
hybrida L.). Mutant plants lacking chalcone synthase (CHS), which catalyzes
the first committed step in flavonoid synthesis, do not accumulate
flavonols and are self-sterile. The mutant pollen can be induced to
germinate by supplementing it with kaempferol, a flavonol aglycone, either
at the time of pollination or by addition to an in vitro germination
system. Biochemical complementation occurs naturally when the mutant,
flavonol-deficient pollen is crossed to wild-type, flavonoid-producing
stigmas. We found that successful pollination depends on stigma maturity,
indicating that flavonol aglycone accumulation may be developmentally
regulated. Quantitative immunoblotting, in vitro and in vivo pollen
germination, and high-performance liquid chromatographic analyses of stigma
and anther extracts were used to determine the relationship between CHS
levels and flavonol aglycone accumulation in developing petunia flowers.
Although substantial levels of CHS were measured, we detected no flavonol
aglycones in wild-type stigma or anther extracts. Instead, the occurrence
of a conjugated form (flavonol glycoside) suggests that a mechanism may
operate to convert glycosides to the active aglycone form.
