title: Physical organization and phylogenetic analysis of acdR as leucine-responsive regulator of the 1-aminocyclopropane-1-carboxylate deaminase gene acdS in phytobeneficial Azospirillum lipoferum 4B and other Proteobacteria.
abstract: The phytostimulatory alphaproteobacterium Azospirillum lipoferum 4B exhibits the plant-beneficial gene acdS, which enables deamination of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC). Here, we show that acdS is in the vicinity of acdR, a homolog to leucine-responsive regulator lrp, in A. lipoferum 4B and most other acdS+ Proteobacteria. Unlike in Beta- and Gammaproteobacteria, acdS (and acdR) is preferentially located on symbiotic islands and plasmids in Alphaproteobacteria. In A. lipoferum 4B, acdS was mapped on a 750-kb plasmid that is lost during phenotypic variation, whereas other phytobeneficial genes such as nifH (associative nitrogen fixation) are maintained. In Proteobacteria, the phylogenies of acdR and acdS were largely but not totally congruent, despite physical proximity of the genes, regardless of whether DNA or deduced protein sequences were used. Potential Lrp, cAMP receptor protein (CRP) and fumarate-nitrate reduction regulator (FNR) binding sites were evidenced in the acdS promoter regions of strain 4B and most of 46 other acdS+ Proteobacteria. Indeed, transcriptional and enzymatic analyses done in vitro pointed to the involvement of Lrp- and FNR-like transcriptional up-regulation of ACC deaminase activity in A. lipoferum 4B. This is the first synteny, phylogenetic, and functional analysis of factors modulating acdS expression in Azospirillum plant growth-promoting rhizobacterium.
authors.affiliation: Université de Lyon, Lyon, F-69003, France.
authors.forename: Claire
authors.initials: C
authors.lastname: Prigent-Combaret
authors.forename: Didier
authors.initials: D
authors.lastname: Blaha
authors.forename: Joël F
authors.initials: JF
authors.lastname: Pothier
authors.forename: Ludovic
authors.initials: L
authors.lastname: Vial
authors.forename: Marie-Andrée
authors.initials: MA
authors.lastname: Poirier
authors.forename: Florence
authors.initials: F
authors.lastname: Wisniewski-Dyé
authors.forename: Yvan
authors.initials: Y
authors.lastname: Moënne-Loccoz
mesh_terms: D000595:Amino Acid Sequence; D000598:Amino Acids, Cyclic / Q000378:metabolism; D042081:Azospirillum lipoferum / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D019755:Carbon-Carbon Lyases / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D007930:Leucine / Q000378:metabolism; D051756:Leucine-Responsive Regulatory Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010641:Phenotype; D010802:Phylogeny; D020560:Proteobacteria / Q000145:classification / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D000598:Amino Acids, Cyclic; D001426:Bacterial Proteins; D051756:Leucine-Responsive Regulatory Protein; C023863:1-aminocyclopropane-1-carboxylic acid; C033634:1-aminocyclopropane-1-carboxylate deaminase; D019755:Carbon-Carbon Lyases; D007930:Leucine