title: Involvement of the azorhizobial chromosome partition gene (parA) in the onset of bacteroid differentiation during Sesbania rostrata stem nodule development.
abstract: A parA gene in-frame deletion mutant of Azorhizobium caulinodans ORS571 (ORS571-ΔparA) was constructed to evaluate the roles of the chromosome-partitioning gene on various bacterial traits and on the development of stem-positioned nodules. The ΔparA mutant showed a pleiomorphic cell shape phenotype and was polyploid, with differences in nucleoid sizes due to dramatic defects in chromosome partitioning. Upon inoculation of the ΔparA mutant onto the stem of Sesbania rostrata, three types of immature nodule-like structures with impaired nitrogen-fixing activity were generated. Most showed signs of bacteroid early senescence. Moreover, the ΔparA cells within the nodule-like structures exhibited multiple developmental-stage phenotypes. Since the bacA gene has been considered an indicator for bacteroid formation, we applied the expression pattern of bacA as a nodule maturity index in this study. Our data indicate that the bacA gene expression is parA dependent in symbiosis. The presence of the parA gene transcript was inversely correlated with the maturity of nodule; the transcript was switched off in fully mature bacteroids. In summary, our experimental evidence demonstrates that the parA gene not only plays crucial roles in cellular development when the microbe is free-living but also negatively regulates bacteroid formation in S. rostrata stem nodules.
authors.affiliation: Institute of Biotechnology, National Taiwan University, R412, No. 81, Chang-Xing St., Taipei 106, Taiwan. chiteliu@ntu.edu.tw
authors.forename: Chi-Te
authors.initials: CT
authors.lastname: Liu
authors.forename: Kyung-Bum
authors.initials: KB
authors.lastname: Lee
authors.forename: Yu-Sheng
authors.initials: YS
authors.lastname: Wang
authors.forename: Min-Hua
authors.initials: MH
authors.lastname: Peng
authors.forename: Kung-Ta
authors.initials: KT
authors.lastname: Lee
authors.forename: Shino
authors.initials: S
authors.lastname: Suzuki
authors.forename: Tadahiro
authors.initials: T
authors.lastname: Suzuki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Oyaizu
mesh_terms: D020599:Azorhizobium caulinodans / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism / Q000502:physiology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D026901:Membrane Transport Proteins / Q000378:metabolism; D009586:Nitrogen Fixation; D018547:Plant Stems / Q000382:microbiology* / Q000502:physiology; D049931:Sesbania / Q000382:microbiology* / Q000502:physiology; D013559:Symbiosis
chemical_list: D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; C052883:chromosome partition proteins, bacterial