RESUMO
Our previous study indicated org35 was involved in chemotaxis and interacted with nitrogen fixation transcriptional activator NifA via PAS domain. In order to reveal the role of org35 in nitrogen regulation, the downstream target genes of org35 were identified. We here report differentially expressed genes in org35 mutants comparing with wild type Sp7 by means of cDNA-AFLP. Four up-regulated transcript-derived fragments (TDFs) homologues of chemotaxis transduction proteins were found, including CheW, methyl-accepting chemotaxis protein and response regulator CheY-like receiver. Three distinct TDFs (AB46, AB58 and AB63) were similar to PHB de-polymerase C-terminus, cell shape-determining protein and flagellin domain protein. And 11 TDFs showed similarities with signal transduction proteins, including homologous protein of the nitrogen regulation protein NtrY and nitrate/nitrite response regulator protein NarL. These data suggested that the Azospirillum brasilense org35 was a multi-effecter and involved in chemotaxis, cyst development and regulation of nitrogen fixation.
Assuntos
Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , Azospirillum brasilense/fisiologia , Quimiotaxia , DNA Complementar/genética , Perfilação da Expressão Gênica , Regulação Bacteriana da Expressão Gênica , Fatores de Transcrição/metabolismo , Azospirillum brasilense/genética , Azospirillum brasilense/crescimento & desenvolvimento , Deleção de Genes , Mutagênese Insercional , Regulon , Transdução de Sinais , Fatores de Transcrição/genéticaRESUMO
We here report the sequence and functional analysis of cstB of Azospirillum brasilense Sp7. The predicted cstB contains C-terminal two PAS domains and N-terminal part which has similarity with CheB-CheR fusion protein. cstB mutants had reduced swarming ability compared to that of A. brasilense wild-type strain, implying that cstB was involved in chemotaxis in A. brasilense. A microscopic analysis revealed that cstB mutants developed mature cyst cells more quickly than wild type, indicating that cstB is involved in cyst formation. cstB mutants were affected in colony morphology and the production of exopolysaccharides (EPS) which are essential for A. brasilense cells to differentiate into cyst-like forms. These observations suggested that cstB was a multi-effector involved in cyst development and chemotaxis in A. brasilense.
Assuntos
Azospirillum brasilense/citologia , Azospirillum brasilense/fisiologia , Proteínas de Bactérias/metabolismo , Quimiotaxia , Fusão Gênica , Metiltransferases/metabolismo , Azospirillum brasilense/genética , Azospirillum brasilense/crescimento & desenvolvimento , Proteínas de Bactérias/genética , DNA Bacteriano/química , DNA Bacteriano/genética , Deleção de Genes , Locomoção , Metiltransferases/genética , Dados de Sequência Molecular , Polissacarídeos Bacterianos/metabolismo , Estrutura Terciária de Proteína , Análise de Sequência de DNARESUMO
We here report the sequence and functional analysis of org35 of Azospirillum brasilense Sp7, which was originally identified to be able to interact with NifA in yeast-two-hybrid system. The org35 encodes a hybrid two-component system protein, including N-terminal PAS domains, a histidine kinase (HPK) domain and a response regulator (RR) domain in C-terminal. To determine the function of the Org35, a deletion-insertion mutant in PAS domain [named Sp7353] and a complemental strain Sp7353C were constructed. The mutant had reduced chemotaxis ability compared to that of wild-type, and the complemental strain was similar to the wild-type strain. These data suggested that the A. brasilense org35 played a key role in chemotaxis. Variants containing different domains of the org35 were expressed, and the functions of these domains were studied in vitro. Phosphorylation assays in vitro demonstrated that the HPK domain of Org35 possessed the autokinase activity and that the phosphorylated HPK was able to transfer phosphate groups to the RR domain. The result indicated Org35 was a phosphorylation-communicating protein.