cDNA-AFLP reveals differentially expressed genes related to cell aggregation of Azospirillum brasilense.
The response regulatory gene flcA controls the differentiation process of Azospirillum brasilense from vegetative state to cyst-like forms, both in culture and in association with plants. In contrast to the wild type parental strain Sp7, strain Sp72002, a Tn5 induced flcA(-) mutant, does not aggregate, does not differentiate from motile, vibroid cells into nonmotile, cyst-like forms and lacks some of the exopolysaccharide material on its cell surface. Here we aimed to identify differentially expressed genes whose expression could be modulated by flcA. Using cDNA-amplified fragment length polymorphism, we detected 81 transcript-derived fragments showing differential expression during exponential growth phase in an aggregation-inducing medium containing high C : N ratio. The fragments were sequenced and analyzed, and expression of ten genes encoding known proteins was compared between the two strains by reverse transcriptase polymerase chain reaction-(RT-PCR). RT-PCR analyses confirmed the differential patterns observed by cDNA-AFLP in nine of those genes. Among them are genes homologous to nodQ, involved in sulfation; narK, involved in nitrite/nitrate transport, and flp, involved in autoaggregation; as well as genes encoding a biopolymer transport protein, and the signal recognition particle. This work demonstrates the usefulness of the cDNA-AFLP approach to reveal genes that are differentially expressed during aggregation in Azospirillum brasilense and provides insights into the aggregation process of this bacterium.
Valverde
Angel
A
Department of Plant Pathology and Microbiology, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot, Israel.
Okon
Yaacov
Y
Burdman
Saul
S
D000595:Amino Acid Sequence; D015806:Azospirillum brasilense / Q000235:genetics* / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics*; D018076:DNA, Complementary; D005427:Flocculation; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D008969:Molecular Sequence Data; D021141:Nucleic Acid Amplification Techniques; D011110:Polymorphism, Genetic; D011135:Polysaccharides, Bacterial / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics*
D001426:Bacterial Proteins; D018076:DNA, Complementary; C111095:FlcA protein, Azospirillum brasilense; D011135:Polysaccharides, Bacterial; D014157:Transcription Factors