title: A Medicago truncatula Cystathionine-β-Synthase-like Domain-Containing Protein Is Required for Rhizobial Infection and Symbiotic Nitrogen Fixation.
abstract: The symbiosis between leguminous plants and soil rhizobia culminates in the formation of nitrogen-fixing organs called nodules that support plant growth. Two Medicago truncatula Tnt1-insertion mutants were identified that produced small nodules, which were unable to fix nitrogen effectively due to ineffective rhizobial colonization. The gene underlying this phenotype was found to encode a protein containing a putative membrane-localized domain of unknown function (DUF21) and a cystathionine-β-synthase domain. The cbs1 mutants had defective infection threads that were sometimes devoid of rhizobia and formed small nodules with greatly reduced numbers of symbiosomes. We studied the expression of the gene, designated M truncatula Cystathionine-β-Synthase-like1 (MtCBS1), using a promoter-β-glucuronidase gene fusion, which revealed expression in infected root hair cells, developing nodules, and in the invasion zone of mature nodules. An MtCBS1-GFP fusion protein localized itself to the infection thread and symbiosomes. Nodulation factor-induced Ca(2+) responses were observed in the cbs1 mutant, indicating that MtCBS1 acts downstream of nodulation factor signaling. MtCBS1 expression occurred exclusively during Medicago-rhizobium symbiosis. Induction of MtCBS1 expression during symbiosis was found to be dependent on Nodule Inception (NIN), a key transcription factor that controls both rhizobial infection and nodule organogenesis. Interestingly, the closest homolog of MtCBS1, MtCBS2, was specifically induced in mycorrhizal roots, suggesting common infection mechanisms in nodulation and mycorrhization. Related proteins in Arabidopsis have been implicated in cell wall maturation, suggesting a potential role for CBS1 in the formation of the infection thread wall.
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73401 (S.S., J.N., S.Z., J.W., I.T.-J., M.K.U.); and John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK (C.L., A.B., D.G., S.S., I.T.-J., G.O., J.D.M.).
authors.forename: Senjuti
authors.identifier: 0000-0003-2323-2587
authors.initials: S
authors.lastname: Sinharoy
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73401 (S.S., J.N., S.Z., J.W., I.T.-J., M.K.U.); and John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK (C.L., A.B., D.G., S.S., I.T.-J., G.O., J.D.M.).
authors.forename: Chengwu
authors.identifier: 0000-0002-6650-6245
authors.initials: C
authors.lastname: Liu
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73401 (S.S., J.N., S.Z., J.W., I.T.-J., M.K.U.); and John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK (C.L., A.B., D.G., S.S., I.T.-J., G.O., J.D.M.).
authors.forename: Andrew
authors.initials: A
authors.lastname: Breakspear
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73401 (S.S., J.N., S.Z., J.W., I.T.-J., M.K.U.); and John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK (C.L., A.B., D.G., S.S., I.T.-J., G.O., J.D.M.).
authors.forename: Dian
authors.initials: D
authors.lastname: Guan
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73401 (S.S., J.N., S.Z., J.W., I.T.-J., M.K.U.); and John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK (C.L., A.B., D.G., S.S., I.T.-J., G.O., J.D.M.).
authors.forename: Sarah
authors.identifier: 0000-0003-0399-9588
authors.initials: S
authors.lastname: Shailes
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73401 (S.S., J.N., S.Z., J.W., I.T.-J., M.K.U.); and John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK (C.L., A.B., D.G., S.S., I.T.-J., G.O., J.D.M.).
authors.forename: Jin
authors.initials: J
authors.lastname: Nakashima
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73401 (S.S., J.N., S.Z., J.W., I.T.-J., M.K.U.); and John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK (C.L., A.B., D.G., S.S., I.T.-J., G.O., J.D.M.).
authors.forename: Shulan
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73401 (S.S., J.N., S.Z., J.W., I.T.-J., M.K.U.); and John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK (C.L., A.B., D.G., S.S., I.T.-J., G.O., J.D.M.).
authors.forename: Jiangqi
authors.identifier: 0000-0001-5113-7750
authors.initials: J
authors.lastname: Wen
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73401 (S.S., J.N., S.Z., J.W., I.T.-J., M.K.U.); and John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK (C.L., A.B., D.G., S.S., I.T.-J., G.O., J.D.M.).
authors.forename: Ivone
authors.initials: I
authors.lastname: Torres-Jerez
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73401 (S.S., J.N., S.Z., J.W., I.T.-J., M.K.U.); and John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK (C.L., A.B., D.G., S.S., I.T.-J., G.O., J.D.M.).
authors.forename: Giles
authors.initials: G
authors.lastname: Oldroyd
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73401 (S.S., J.N., S.Z., J.W., I.T.-J., M.K.U.); and John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK (C.L., A.B., D.G., S.S., I.T.-J., G.O., J.D.M.).
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: Murray
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73401 (S.S., J.N., S.Z., J.W., I.T.-J., M.K.U.); and John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK (C.L., A.B., D.G., S.S., I.T.-J., G.O., J.D.M.) mudvardi@noble.org.
authors.forename: Michael K
authors.initials: MK
authors.lastname: Udvardi
mesh_terms: D003541:Cystathionine beta-Synthase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004705:Endocytosis; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D049452:Green Fluorescent Proteins / Q000378:metabolism; D046913:Medicago truncatula / Q000201:enzymology* / Q000235:genetics / Q000382:microbiology*; D009154:Mutation / Q000235:genetics; D009586:Nitrogen Fixation; D010641:Phenotype; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D055170:Plant Root Nodulation; D011401:Promoter Regions, Genetic / Q000235:genetics; D000072417:Protein Domains; D012231:Rhizobium / Q000502:physiology*; D053204:Root Nodules, Plant / Q000235:genetics; D013559:Symbiosis
chemical_list: D010940:Plant Proteins; D049452:Green Fluorescent Proteins; D003541:Cystathionine beta-Synthase