Modification of phenolic metabolism in soybean hairy roots through down regulation of chalcone synthase or isoflavone synthase |
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Authors: | Vera V Lozovaya Anatoliy V Lygin Olga V Zernova Alexander V Ulanov Shuxian Li Glen L Hartman Jack M Widholm |
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Institution: | (1) Department of Crop Sciences, University of Illinois, 1201 W. Gregory Dr., Urbana, IL 61801, USA;(2) USDA, Agricultural Research Service, University of Illinois, 1101 W. Peabody Dr., Urbana, IL 61801, USA;(3) USDA/ARS, MSA, CGPRU, 141 Experiment Station Road, P.O. Box 345, Stoneville, MS 38776, USA |
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Abstract: | Soybean hairy roots, transformed with the soybean chalcone synthase (CHS6) or isoflavone synthase (IFS2) genes, with dramatically decreased capacity to synthesize isoflavones were produced to determine what effects these changes
would have on susceptibility to a fungal pathogen. The isoflavone and coumestrol concentrations were decreased by about 90%
in most lines apparently due to gene silencing. The IFS2 transformed lines had very low IFS enzyme activity in microsomal fractions as measured by the conversion of naringenin to
genistein. The CHS6 lines with decreased isoflavone concentrations had 5 to 20-fold lower CHS enzyme activities than the appropriate controls.
Both IFS2 and CHS transformed lines accumulated higher concentrations of both soluble and cell wall bound phenolic acids compared to controls
with higher levels found in the CHS6 lines indicating alterations in the lignin biosynthetic branch of the pathway. Induction of the soybean phytoalexin glyceollin,
of which the precursor is the isoflavone daidzein, by the fungal pathogen Fusarium solani f. sp. glycines (FSG) that causes soybean sudden death syndrome (SDS) showed that the low isoflavone transformed lines did not accumulate
glyceollin while the control lines did. The (iso)liquritigenin content increased upon FSG induction in the IFS2 transformed
roots indicating that the pathway reactions before this point can control isoflavonoid synthesis. The lowest fungal growth
rate on hairy roots was found on the FSG partially resistant control roots followed by the SDS sensitive control roots and
the low isoflavone transformants. The results indicate the importance of phytoalexin synthesis in root resistance to the pathogen.
Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard
of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also
be suitable. |
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Keywords: | Disease Genetic engineering Phenylpropanoids Resistance Hairy roots Soybean |
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