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Phytotropins: receptors and endogenous ligands
1University of Cambridge, Department of Biochemistry, England.
Symposia of the Society for Experimental Biology
|January 1, 1990
Summary
Plant hormones called phytotropins regulate growth responses. Recent studies suggest flavonoids like quercetin may act as natural regulators of auxin transport by interacting with the phytotropin receptor.
Area of Science:
- Plant Biology
- Biochemistry
- Molecular Biology
Background:
- Phytotropins are compounds inhibiting plant gravitropism, phototropism, and auxin transport.
- 1-N-naphthylphthalamic acid (NPA) is a key synthetic phytotropin, binding to a plasma membrane receptor.
- Not all polar auxin transport inhibitors (PATIS) are phytotropins; exceptions include triiodobenzoic acid and morphactins.
Purpose of the Study:
- To investigate potential endogenous regulators of auxin transport that interact with the NPA receptor.
- To explore the role of flavonoid compounds in modulating auxin transport pathways.
Main Methods:
- Structure-activity relationship analysis of phytotropins and related compounds.
- Assays for inhibition of NPA binding to the receptor.
- Assessment of effects on transmembrane and polar auxin transport.
Main Results:
- Certain C-15 flavonoids, including quercetin and apigenin, exhibit NPA-like effects and inhibit NPA binding.
- Active flavonoids require specific structural features: hydroxyl groups on A and B rings, linked by a pyrone ring.
- Flavonoid aglycones are active, while glycosides are not; exceptions like morin and genistein show differential binding and transport effects.
Conclusions:
- Flavonoids are potential endogenous regulators of auxin transport, acting via the NPA receptor.
- The structural requirements for flavonoid activity suggest a specific binding interaction.
- Environmental control over flavonoid synthesis parallels that of auxin transport, hinting at coordinated regulation.
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