Identification of salt stress inducible genes that control cell envelope related functions in <Emphasis Type="Italic">Azospirillum brasilense</Emphasis> Sp7 |
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Authors: | Thirunavukkarasu Nagarajan Jos Vanderleyden Anil Kumar Tripathi |
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Institution: | (1) Bacterial Genetics Laboratory, School of Biotechnology, Faculty of Science, Banaras Hindu University, Varanasi, 221005, India;(2) Centre for Microbial and Plant Genetics, K.U. Leuven, Kasteelpark Arenberg 20, 3001 Leuven, Belgium |
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Abstract: | Plant growth promoting rhizobacteria such as Azospirillum brasilense are agronomically important as they are frequently used for crop inoculation. But adverse factors such as increasing soil
salinity limit their survival, multiplication and phytostimulatory effect. In order to understand the role of the genes involved
in the adaptation of A. brasilense Sp7 to salt stress, a mutant library (6,800 mutants) was constructed after random integration of a mini-Transposon Tn5 derivative
containing a promoterless gusA and oriV. The library was screened for salt stress inducible Gus activity on minimal malate agar medium containing NaCl and 5-bromo-4-chloro-3-indolyl-β-d-glucuronide. Salt stress responsiveness of the promoters was estimated by quantifying GusA activity in the presence and absence
of NaCl stress using p-nitrophenyl-β-d-glucuronide as a substrate. In 11 mutants showing high levels of gusA expression in the presence of salt-stress, the partial nucleotide sequence of the DNA region flanking the site of Tn5 insertion
was determined and analysed using the NCBI-BLAST programs. Similarity searches revealed that 10 out of the 11 genes sequenced
showed notable similarity with genes involved in functions related to modulation in the composition of exopolysaccharides,
capsular polysaccharides, lipopolysaccharides, peptidoglycan and lipid bilayer of the cell envelope. Induction of cell envelope
related genes in response to salt stress and salt sensitive phenotype of several mutants in A. brasilense indicate a prominent role of cell envelope in salt-stress adaptation. |
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Keywords: | Azosprillum brasilense Transposon mutagenesis Salinity-stress induced genes |
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