| Autor: |
Jacques Batut, P. Boistard, B. Boesten |
| Rok vydání: |
1998 |
| Předmět: |
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| Zdroj: |
Biological Nitrogen Fixation for the 21st Century ISBN: 9789401061698 |
| DOI: |
10.1007/978-94-011-5159-7_166 |
| Popis: |
C4-dicarboxylic acids (dCA) are the only source of carbon partitioned to the bacteroids in sufficient amounts to sustain symbiotic N2-fixation. Accordingly efficient expression of the R. meliloti dctA gene, coding for a dCA uptakepermease is essential for symbiotic nitrogen fixation. The gene is expressed from a σ54 type promoter and under free-living conditions is induced in the presence of dCA. Induction is fully dependent on the regulatory dctBD genes which code for a two component regulatory system. The transcriptional activator DctD interacts with enhancer sequences (UAS) located upstream from the promoter. During symbiosis with the Medicago sativa (alfalfa) host plant, the dctA gene is expressed even when the dctBD genes are mutated. This implies an alternative mechanism of symbiotic activation (ASA). In order to evaluate the role of the ASA we monitored the in situ expression of the dctA gene in wild-type and dctD mutant strains during symbiosis with alfalfa. A number of gene fusions of dctA to the lacZ reporter gene were constructed. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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