Host: The Japanese Society of Plant Physiologists
Pages 0177
Rautenberg and Kuhn observed in 1864 that nitrogen sources inhibit nodulation. Since then, it has been shown that leguminous hypernodulating mutants (har1 etc.) exhibit a nitrate-tolerant phenotype. However little is known about the molecular mechanism.
In L. japonicus HAR1 is involved in systemic regulation of nodulation. Okamoto in our laboratory found that LjCLE1 and LjCLE2 are significantly up-regulated in response to Mesorhizobium loti and have the strong ability to suppress nodulation via HAR1. So we noticed that har1 mutant exhibits a nitrate-tolerant phenotype in nodulation and searched for LjCLE induced by nitrate treatment.
Expression analysis revealed that LjCLE2 among 32 LjCLE genes was specifically and significantly up-regulated by 10 mM nitrate. The increase of transcript level induced by rhizobial infection was cancelled by pretreatment of 10 mM nitrate. Based on these results, we propose a model in which LjCLE2 induced by nitrate suppresses nodulation via HAR1-mediated signaling.
