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.
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.
Yano
Koji
K
National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8602, Japan.
Shibata
Satoshi
S
Chen
Wen-Li
WL
Sato
Shusei
S
Kaneko
Takakazu
T
Jurkiewicz
Anna
A
Sandal
Niels
N
Banba
Mari
M
Imaizumi-Anraku
Haruko
H
Kojima
Tomoko
T
Ohtomo
Ryo
R
Szczyglowski
Krzysztof
K
Stougaard
Jens
J
Tabata
Satoshi
S
Hayashi
Makoto
M
Kouchi
Hiroshi
H
Umehara
Yosuke
Y
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
D018744:DNA, Plant; D010940:Plant Proteins