title: CERBERUS, a novel U-box protein containing WD-40 repeats, is required for formation of the infection thread and nodule development in the legume-Rhizobium symbiosis.
abstract: Endosymbiotic infection of legume plants by Rhizobium bacteria is initiated through infection threads (ITs) which are initiated within and penetrate from root hairs and deliver the endosymbionts into nodule cells. Despite recent progress in understanding the mutual recognition and early symbiotic signaling cascades in host legumes, the molecular mechanisms underlying bacterial infection processes and successive nodule organogenesis are still poorly understood. We isolated a novel symbiotic mutant of Lotus japonicus, cerberus, which shows defects in IT formation and nodule organogenesis. Map-based cloning of the causal gene allowed us to identify the CERBERUS gene, which encodes a novel protein containing a U-box domain and WD-40 repeats. CERBERUS expression was detected in the roots and nodules, and was enhanced after inoculation of Mesorhizobium loti. Strong expression was detected in developing nodule primordia and the infected zone of mature nodules. In cerberus mutants, Rhizobium colonized curled root hair tips, but hardly penetrated into root hair cells. The occasional ITs that were formed inside the root hair cells were mostly arrested within the epidermal cell layer. Nodule organogenesis was aborted prematurely, resulting in the formation of a large number of small bumps which contained no endosymbiotic bacteria. These phenotypic and genetic analyses, together with comparisons with other legume mutants with defects in IT formation, indicate that CERBERUS plays a critical role in the very early steps of IT formation as well as in growth and differentiation of nodules.
authors.affiliation: National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8602, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Yano
authors.forename: Satoshi
authors.initials: S
authors.lastname: Shibata
authors.forename: Wen-Li
authors.initials: WL
authors.lastname: Chen
authors.forename: Shusei
authors.initials: S
authors.lastname: Sato
authors.forename: Takakazu
authors.initials: T
authors.lastname: Kaneko
authors.forename: Anna
authors.initials: A
authors.lastname: Jurkiewicz
authors.forename: Niels
authors.initials: N
authors.lastname: Sandal
authors.forename: Mari
authors.initials: M
authors.lastname: Banba
authors.forename: Haruko
authors.initials: H
authors.lastname: Imaizumi-Anraku
authors.forename: Tomoko
authors.initials: T
authors.lastname: Kojima
authors.forename: Ryo
authors.initials: R
authors.lastname: Ohtomo
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Szczyglowski
authors.forename: Jens
authors.initials: J
authors.lastname: Stougaard
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tabata
authors.forename: Makoto
authors.initials: M
authors.lastname: Hayashi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kouchi
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Umehara
mesh_terms: D000595:Amino Acid Sequence; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D018744:DNA, Plant / Q000235:genetics; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D000070116:Lotus / Q000235:genetics* / Q000382:microbiology; D008969:Molecular Sequence Data; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D012231:Rhizobium / Q000502:physiology*; D053204:Root Nodules, Plant / Q000254:growth & development* / Q000382:microbiology; D016415:Sequence Alignment; D013559:Symbiosis
chemical_list: D018744:DNA, Plant; D010940:Plant Proteins