Nod factor/nitrate-induced CLE genes that drive HAR1-mediated systemic regulation of nodulation.
Host legumes control root nodule numbers by sensing external and internal cues. A major external cue is soil nitrate, whereas a feedback regulatory system in which earlier formed nodules suppress further nodulation through shoot-root communication is an important internal cue. The latter is known as autoregulation of nodulation (AUT), and is believed to consist of two long-distance signals: a root-derived signal that is generated in infected roots and transmitted to the shoot; and a shoot-derived signal that systemically inhibits nodulation. In Lotus japonicus, the leucine-rich repeat receptor-like kinase, HYPERNODULATION ABERRANT ROOT FORMATION 1 (HAR1), mediates AUT and nitrate inhibition of nodulation, and is hypothesized to recognize the root-derived signal. Here we identify L. japonicus CLE-Root Signal 1 (LjCLE-RS1) and LjCLE-RS2 as strong candidates for the root-derived signal. A hairy root transformation study shows that overexpressing LjCLE-RS1 and -RS2 inhibits nodulation systemically and, furthermore, that the systemic suppression depends on HAR1. Moreover, LjCLE-RS2 expression is strongly up-regulated in roots by nitrate addition. Based on these findings, we propose a simple model for AUT and nitrate inhibition of nodulation mediated by LjCLE-RS1, -RS2 peptides and the HAR1 receptor-like kinase.
Okamoto
Satoru
S
Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo, Tokyo, Japan.
Ohnishi
Erika
E
Sato
Shusei
S
Takahashi
Hirokazu
H
Nakazono
Mikio
M
Tabata
Satoshi
S
Kawaguchi
Masayoshi
M
D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D018745:Genome, Plant; D000070116:Lotus / Q000235:genetics* / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism; D009586:Nitrogen Fixation; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018749:RNA, Plant / Q000235:genetics; D012230:Rhizobiaceae / Q000502:physiology; D053204:Root Nodules, Plant / Q000235:genetics* / Q000378:metabolism; D013559:Symbiosis; D014170:Transformation, Genetic
D009566:Nitrates; D010940:Plant Proteins; D018749:RNA, Plant