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A Chalcone and Two Related Flavonoids Released from Alfalfa Roots Induce nod Genes of Rhizobium meliloti  

A Chalcone and Two Related Flavonoids Released from Alfalfa Roots Induce nod Genes of Rhizobium... Abstract Flavonoid signals from alfalfa (Medicago sativa L.) induce transcription of nodulation (nod) genes in Rhizobium meliloti. Previous investigations identified the flavone luteolin as an active inducer in alfalfa seed extracts, but the nature of nod inducers released from roots has not been reported. Root exudate from 3-day-old alfalfa seedlings was purified and then assayed for biological activity with a nodABC-lacZ fusion in R. meliloti. Indentities of major nod inducers were established by spectroscopic analyses (ultraviolet/visible, proton nuclear magnetic resonance, and mass spectroscopy) and comparison with authentic standards. Major nod inducers, which were identified as 4′,7-dihydroxyflavone, 4′-7-dihydroxyflavanone, and 4,4′-dihydroxy-2′-methoxychalcone, were released from seedling roots at 54, 22, and 20 picomole·plant−1·day−1, respectively. Luteolin was not found in these root exudates. The 4,4′-dihydroxy-2′-methoxychalcone induced nod genes at a concentration one order of magnitude lower than luteolin and is the first naturally released chalcone reported to have this function. Moderate and weak nod-inducing activity was associated, respectively, with 4′,7-dihydroxyflavone and 4′,7-dihydroxyflavanone. 1 Supported in part by U.S. Department of Agriculture CRGO grant 87-CRCR-1-2552 and grant IS-1348-87 from BARD, the U.S.-Israel Binational Agricultural Research and Development Fund. U. A. H. was supported by the Swiss National Research Foundation. This content is only available as a PDF. © 1989 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Plant Physiology Oxford University Press

A Chalcone and Two Related Flavonoids Released from Alfalfa Roots Induce nod Genes of Rhizobium meliloti  

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References (25)

Publisher
Oxford University Press
Copyright
Copyright © 2021 American Society of Plant Biologists
ISSN
0032-0889
eISSN
1532-2548
DOI
10.1104/pp.91.3.842
Publisher site
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Abstract

Abstract Flavonoid signals from alfalfa (Medicago sativa L.) induce transcription of nodulation (nod) genes in Rhizobium meliloti. Previous investigations identified the flavone luteolin as an active inducer in alfalfa seed extracts, but the nature of nod inducers released from roots has not been reported. Root exudate from 3-day-old alfalfa seedlings was purified and then assayed for biological activity with a nodABC-lacZ fusion in R. meliloti. Indentities of major nod inducers were established by spectroscopic analyses (ultraviolet/visible, proton nuclear magnetic resonance, and mass spectroscopy) and comparison with authentic standards. Major nod inducers, which were identified as 4′,7-dihydroxyflavone, 4′-7-dihydroxyflavanone, and 4,4′-dihydroxy-2′-methoxychalcone, were released from seedling roots at 54, 22, and 20 picomole·plant−1·day−1, respectively. Luteolin was not found in these root exudates. The 4,4′-dihydroxy-2′-methoxychalcone induced nod genes at a concentration one order of magnitude lower than luteolin and is the first naturally released chalcone reported to have this function. Moderate and weak nod-inducing activity was associated, respectively, with 4′,7-dihydroxyflavone and 4′,7-dihydroxyflavanone. 1 Supported in part by U.S. Department of Agriculture CRGO grant 87-CRCR-1-2552 and grant IS-1348-87 from BARD, the U.S.-Israel Binational Agricultural Research and Development Fund. U. A. H. was supported by the Swiss National Research Foundation. This content is only available as a PDF. © 1989 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Journal

Plant Physiology – Oxford University Press

Published: Nov 1, 1989

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