Abstract
Rhizobia are soil bacteria which symbiotically infect legume roots and generate nodules in which they fix atmospheric nitrogen for the plant in exchange for photosynthetically fixed carbon. A crucial aspect of signal exchange between these symbionts is the secretion of phenolic compounds by the host root which induce nodulation gene expression in the bacteria. Stimulation of nod gene expression by host phenolics is required for nodule formation, is biochemically specific at 10-6M, and is mediated by nodD. We and others have shown that rhizobia display chemotaxis to 10-9M of the same phenolic compounds. Chemotaxis to inducer phenolics is selectively reduced or abolished by mutations in certain nod genes governing nodulation efficiency or host specificity. Conversely, mutations in rhizobia that affect general motility or chemotaxis have substantial effects on nodulation efficiency and competitiveness. These findings suggest that microbes entering the rhizosphere environment may utilize minor, non-nutrient components in root exudates as signals to guide their movement towards the root surface and elicit changes in gene expression appropriate to this environment.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 45-52 |
| Number of pages | 8 |
| Journal | Plant and Soil |
| Volume | 129 |
| Issue number | 1 |
| DOIs | |
| State | Published - Dec 1 1990 |
| Externally published | Yes |
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Keywords
- Rhizobium
- chemoattractants
- luteolin
- nod gene
- nodulation
- phenolics
- symbiosis
ASJC Scopus subject areas
- Soil Science
- Plant Science
Cite this
Chemotaxis, induced gene expression and competitiveness in the rhizosphere. / Bauer, Wolfgang D.; Caetano-Anollés, Gustavo.
In: Plant and Soil, Vol. 129, No. 1, 01.12.1990, p. 45-52.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Chemotaxis, induced gene expression and competitiveness in the rhizosphere
AU - Bauer, Wolfgang D.
AU - Caetano-Anollés, Gustavo
PY - 1990/12/1
Y1 - 1990/12/1
N2 - Rhizobia are soil bacteria which symbiotically infect legume roots and generate nodules in which they fix atmospheric nitrogen for the plant in exchange for photosynthetically fixed carbon. A crucial aspect of signal exchange between these symbionts is the secretion of phenolic compounds by the host root which induce nodulation gene expression in the bacteria. Stimulation of nod gene expression by host phenolics is required for nodule formation, is biochemically specific at 10-6M, and is mediated by nodD. We and others have shown that rhizobia display chemotaxis to 10-9M of the same phenolic compounds. Chemotaxis to inducer phenolics is selectively reduced or abolished by mutations in certain nod genes governing nodulation efficiency or host specificity. Conversely, mutations in rhizobia that affect general motility or chemotaxis have substantial effects on nodulation efficiency and competitiveness. These findings suggest that microbes entering the rhizosphere environment may utilize minor, non-nutrient components in root exudates as signals to guide their movement towards the root surface and elicit changes in gene expression appropriate to this environment.
AB - Rhizobia are soil bacteria which symbiotically infect legume roots and generate nodules in which they fix atmospheric nitrogen for the plant in exchange for photosynthetically fixed carbon. A crucial aspect of signal exchange between these symbionts is the secretion of phenolic compounds by the host root which induce nodulation gene expression in the bacteria. Stimulation of nod gene expression by host phenolics is required for nodule formation, is biochemically specific at 10-6M, and is mediated by nodD. We and others have shown that rhizobia display chemotaxis to 10-9M of the same phenolic compounds. Chemotaxis to inducer phenolics is selectively reduced or abolished by mutations in certain nod genes governing nodulation efficiency or host specificity. Conversely, mutations in rhizobia that affect general motility or chemotaxis have substantial effects on nodulation efficiency and competitiveness. These findings suggest that microbes entering the rhizosphere environment may utilize minor, non-nutrient components in root exudates as signals to guide their movement towards the root surface and elicit changes in gene expression appropriate to this environment.
KW - Rhizobium
KW - chemoattractants
KW - luteolin
KW - nod gene
KW - nodulation
KW - phenolics
KW - symbiosis
UR - http://www.scopus.com/inward/record.url?scp=0002509728&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0002509728&partnerID=8YFLogxK
U2 - 10.1007/BF00011690
DO - 10.1007/BF00011690
M3 - Article
AN - SCOPUS:0002509728
VL - 129
SP - 45
EP - 52
JO - Plant and Soil
JF - Plant and Soil
SN - 0032-079X
IS - 1
ER -