title: [Identification and functional characterization of genes induced by seed exudates in Azorhizobium caulinodans ORS571].
abstract: OBJECTIVE
  To identify genes induced by plant seed exudates in Azorhizobium caulinodans ORS571.
  
  
  METHODS
  Using promoterless kanamycin resistance gene (Km(r)) on transposon as reporter gene and seed exudates as inducers, we screened genes of interest from transposon insertion mutants libraries. We streaked mutants on TY solid medium with Km, and another with Km and seed exudates correspondingly. If Km(r) is inserted into a gene that can be induced by plant signals, Km(r) will possibly express at the same time. Thus, mutants were selected that can grow on medium with Km and exudates, rather than on medium with Km.
  
  
  RESULTS
  We identified a lysE family gene named asiE in strain Azc0 that can be induced by seed exudates and further analysis indicated that the inducing substance is canavanine (CAN). lacZ transcriptional fusion of asiE confirmed that its expression increased by ten-fold or so under the induction of CAN. Besides, lysE gene in four different species of Rhizobia can be induced by CAN. lysE mutants are all sensitive to CAN treatment whereas wild type are resistant.
  
  
  CONCLUSIONS
  The existence of LysE can make rhizobia better survived in the rhizosphere and may play an important role in early stage of interaction between rhizobia and host plant.
authors.affiliation: College of Life Science, Nanjing Agricultural University, Nanjing 210095, China. caiwentong@163.com
authors.forename: Wentong
authors.initials: W
authors.lastname: Cai
authors.forename: Tao
authors.initials: T
authors.lastname: Cai
authors.forename: Jiang
authors.initials: J
authors.lastname: Zhang
authors.forename: Huiming
authors.initials: H
authors.lastname: Zheng
authors.forename: Zengtao
authors.initials: Z
authors.lastname: Zhong
authors.forename: Jun
authors.initials: J
authors.lastname: Zhu
mesh_terms: D020599:Azorhizobium caulinodans / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002172:Canavanine / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D053147:Plant Exudates / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D012639:Seeds / Q000737:chemistry / Q000378:metabolism; D049931:Sesbania / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D053147:Plant Exudates; D002172:Canavanine