title: MucR Is Required for Transcriptional Activation of Conserved Ion Transporters to Support Nitrogen Fixation of Sinorhizobium fredii in Soybean Nodules.
abstract: To achieve effective symbiosis with legume, rhizobia should fine-tune their background regulation network in addition to activating key genes involved in nodulation (nod) and nitrogen fixation (nif). Here, we report that an ancestral zinc finger regulator, MucR1, other than its paralog, MucR2, carrying a frameshift mutation, is essential for supporting nitrogen fixation of Sinorhizobium fredii CCBAU45436 within soybean nodules. In contrast to the chromosomal mucR1, mucR2 is located on symbiosis plasmid, indicating its horizontal transfer potential. A MucR2 homolog lacking the frameshift mutation, such as the one from S. fredii NGR234, can complement phenotypic defects of the mucR1 mutant of CCBAU45436. RNA-seq analysis revealed that the MucR1 regulon of CCBAU45436 within nodules exhibits significant difference compared with that of free-living cells. MucR1 is required for active expression of transporters for phosphate, zinc, and elements essential for nitrogenase activity (iron, molybdenum, and sulfur) in nodules but is dispensable for transcription of key genes (nif/fix) involved in nitrogen fixation. Further reverse genetics suggests that S. fredii uses high-affinity transporters to meet the demand for zinc and phosphate within nodules. These findings, together with the horizontal transfer potential of the mucR homolog, imply an intriguing evolutionary role of this ancestral regulator in supporting nitrogen fixation.
authors.affiliation: 1 State Key Laboratory of Agrobiotechnology, and College of Biological Sciences, China Agricultural University, Beijing, China;|2 Key Laboratory of Soil Microbiology, Ministry of Agriculture, China Agricultural University, Beijing, China; and.|3 Rhizobium Research Center, China Agricultural University, Beijing, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Jiao
authors.affiliation: 1 State Key Laboratory of Agrobiotechnology, and College of Biological Sciences, China Agricultural University, Beijing, China;|2 Key Laboratory of Soil Microbiology, Ministry of Agriculture, China Agricultural University, Beijing, China; and.|3 Rhizobium Research Center, China Agricultural University, Beijing, China.
authors.forename: Li Juan
authors.initials: LJ
authors.lastname: Wu
authors.affiliation: 1 State Key Laboratory of Agrobiotechnology, and College of Biological Sciences, China Agricultural University, Beijing, China;
authors.forename: Biliang
authors.initials: B
authors.lastname: Zhang
authors.affiliation: 1 State Key Laboratory of Agrobiotechnology, and College of Biological Sciences, China Agricultural University, Beijing, China;|2 Key Laboratory of Soil Microbiology, Ministry of Agriculture, China Agricultural University, Beijing, China; and.|3 Rhizobium Research Center, China Agricultural University, Beijing, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Hu
authors.affiliation: 1 State Key Laboratory of Agrobiotechnology, and College of Biological Sciences, China Agricultural University, Beijing, China;|2 Key Laboratory of Soil Microbiology, Ministry of Agriculture, China Agricultural University, Beijing, China; and.|3 Rhizobium Research Center, China Agricultural University, Beijing, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.affiliation: 1 State Key Laboratory of Agrobiotechnology, and College of Biological Sciences, China Agricultural University, Beijing, China;|2 Key Laboratory of Soil Microbiology, Ministry of Agriculture, China Agricultural University, Beijing, China; and.|3 Rhizobium Research Center, China Agricultural University, Beijing, China.
authors.forename: Xing Xing
authors.initials: XX
authors.lastname: Zhang
authors.affiliation: 1 State Key Laboratory of Agrobiotechnology, and College of Biological Sciences, China Agricultural University, Beijing, China;|2 Key Laboratory of Soil Microbiology, Ministry of Agriculture, China Agricultural University, Beijing, China; and.|3 Rhizobium Research Center, China Agricultural University, Beijing, China.
authors.forename: Hui Juan
authors.initials: HJ
authors.lastname: Guo
authors.affiliation: 1 State Key Laboratory of Agrobiotechnology, and College of Biological Sciences, China Agricultural University, Beijing, China;|2 Key Laboratory of Soil Microbiology, Ministry of Agriculture, China Agricultural University, Beijing, China; and.|3 Rhizobium Research Center, China Agricultural University, Beijing, China.
authors.forename: Li Xue
authors.initials: LX
authors.lastname: Liu
authors.affiliation: 1 State Key Laboratory of Agrobiotechnology, and College of Biological Sciences, China Agricultural University, Beijing, China;|2 Key Laboratory of Soil Microbiology, Ministry of Agriculture, China Agricultural University, Beijing, China; and.|3 Rhizobium Research Center, China Agricultural University, Beijing, China.
authors.forename: Wen Xin
authors.initials: WX
authors.lastname: Chen
authors.affiliation: 1 State Key Laboratory of Agrobiotechnology, and College of Biological Sciences, China Agricultural University, Beijing, China;
authors.forename: Ziding
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: 1 State Key Laboratory of Agrobiotechnology, and College of Biological Sciences, China Agricultural University, Beijing, China;|2 Key Laboratory of Soil Microbiology, Ministry of Agriculture, China Agricultural University, Beijing, China; and.|3 Rhizobium Research Center, China Agricultural University, Beijing, China.
authors.forename: Chang Fu
authors.initials: CF
authors.lastname: Tian
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins; D016368:Frameshift Mutation; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D017136:Ion Transport; D009586:Nitrogen Fixation / Q000502:physiology*; D010802:Phylogeny; D012329:RNA, Bacterial / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D053204:Root Nodules, Plant / Q000382:microbiology*; D042181:Sinorhizobium fredii / Q000378:metabolism*; D013025:Glycine max / Q000382:microbiology*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D012329:RNA, Bacterial