Deregulation of a Ca2+/calmodulin-dependent kinase leads to spontaneous nodule development.
Induced development of a new plant organ in response to rhizobia is the most prominent manifestation of legume root-nodule symbiosis with nitrogen-fixing bacteria. Here we show that the complex root-nodule organogenic programme can be genetically deregulated to trigger de novo nodule formation in the absence of rhizobia or exogenous rhizobial signals. In an ethylmethane sulphonate-induced snf1 (spontaneous nodule formation) mutant of Lotus japonicus, a single amino-acid replacement in a Ca2+/calmodulin-dependent protein kinase (CCaMK) is sufficient to turn fully differentiated root cortical cells into meristematic founder cells of root nodule primordia. These spontaneous nodules are genuine nodules with an ontogeny similar to that of rhizobial-induced root nodules, corroborating previous physiological studies. Using two receptor-deficient genetic backgrounds we provide evidence for a developmentally integrated spontaneous nodulation process that is independent of lipochitin-oligosaccharide signal perception and oscillations in Ca2+ second messenger levels. Our results reveal a key regulatory position of CCaMK upstream of all components required for cell-cycle activation, and a phenotypically divergent series of mutant alleles demonstrates positive and negative regulation of the process.
Tirichine
Leïla
L
Imaizumi-Anraku
Haruko
H
Yoshida
Satoko
S
Murakami
Yasuhiro
Y
Madsen
Lene H
LH
Miwa
Hiroki
H
Nakagawa
Tomomi
T
Sandal
Niels
N
Albrektsen
Anita S
AS
Kawaguchi
Masayoshi
M
Downie
Allan
A
Sato
Shusei
S
Tabata
Satoshi
S
Kouchi
Hiroshi
H
Parniske
Martin
M
Kawasaki
Shinji
S
Stougaard
Jens
J
D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017343:Genes, Plant / Q000235:genetics; D005816:Genetic Complementation Test; D000070116:Lotus / Q000166:cytology / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009586:Nitrogen Fixation / Q000502:physiology*; D010641:Phenotype; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000166:cytology / Q000378:metabolism / Q000382:microbiology / Q000502:physiology
D010940:Plant Proteins; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002118:Calcium