Open AccessIsolation of transposon mutants from Azospirillum brasilense Yu62 and characterization of genes involved in indole‐3‐acetic acid biosynthesis
Author(s) -
Xie Baoen,
Xu Ke,
Zhao Hong Xin,
Chen San Feng
Publication year - 2005
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1016/j.femsle.2005.05.020
Subject(s) - complementation , mutant , biology , azospirillum brasilense , biochemistry , transposon mutagenesis , indole 3 acetic acid , mutagenesis , gene , transposable element , wild type , microbiology and biotechnology , bacteria , genetics , auxin , microbial inoculant
The molecular genetics of indole‐3‐acetic (IAA) synthesis and regulation in Azospirillum brasilense was investigated in this study. Tn5 mutagenesis was performed and five mutants with decreased IAA production were isolated. Five Tn5‐inserted genes from these mutants were cloned and sequenced. Four genes were reported for the first time to be involved in IAA production, namely, atrA , ftsA , omaA and aldA that code for GntR‐family transcriptional regulator, iron‐binding protein component of ABC‐type Fe 3+ transport system, outer membrane protein, and aldehyde dehydrogenase, respectively. In addition, two genes atrB and atrC , with predicted proteins that showed high homology to aminotransferases, were cloned from the downstream of atrA in this bacterium. Studies also showed that complementation of atrA , ftsA and omaA were able to restore the IAA production of the corresponding IAA − mutants. Comparison of Fe 3+ concentrations in culture supernatants of the wild‐type strain, the ftsA mutant and the complemented strain revealed that the iron‐uptake ability of the ftsA mutant was highly reduced. This result also points to the necessity of iron as a metal ion in IAA synthesis. Statistical analysis showed no significant difference in the IAA accumulated in cells between the omaA mutant and the wild‐type strain, suggesting the omaA might not affect IAA secretion but be involved in IAA production in other unknown ways.