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Type: Journal article
Title: Early production of rhizopine in nodules induced by Sinorhizobium meliloti strain L5-30
Author: Heinrich, K.
Ryder, M.
Murphy, P.
Citation: Canadian Journal of Microbiology, 2001; 47(2):165-171
Publisher: Natl Research Council Canada
Issue Date: 2001
ISSN: 0008-4166
Statement of
K Heinrich, M H Ryder, P J Murphy
Abstract: The rhizopine L-3-O-methyl-scyllo-inosamine (3-O-MSI) is metabolized by approximately 10% of the strains of Rhizobium leguminosarum by. viciae and Sinorhizobium meliloti. Rhizopine strains enjoy a substantial competitive advantage in nodulation, which is manifest before 14 days post-inoculation, implying that rhizopine is produced before this time. We were able to detect this compound in the roots of alfalfa (Medicago sativum L. cv. Hunter River) four days after germination (six days post-infection) with S. meliloti strain L5-30 by gas chromatography-mass spectrometry (GC-MS). At four days, nodules were not visible, and the concentration of rhizopine was extremely low, estimated at 67 pg/gfw (picograms/gram fresh weight). The amount increased gradually but remained low until 16 days, when there was a 50-fold increase from day four, by which time nodules were well established. This pattern of synthesis is consistent with previous studies indicating that rhizopine synthesis is regulated by nifA/ntrA regulatory genes, which are maximally expressed in bacteroids at the onset of nitrogen fixation. However, the low level of rhizopine synthesis must be responsible for the early effects on competition for nodulation. Production of rhizopine at this time most likely results from micro-aerobic induction of mos genes in free-living bacteria, either in the infection threads or in the rhizosphere.
Keywords: Sinorhizobium meliloti; Medicago sativa; Plant Roots; Inositol; Gas Chromatography-Mass Spectrometry
RMID: 0020010042
DOI: 10.1139/w00-136
Appears in Collections:Agriculture, Food and Wine publications

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