Two CLE genes are induced by phosphate in roots of Lotus japonicus

Genes of CLE (CLAVATA3/ESR-related) family encode peptide ligands that regulate plant development in response to external stimuli such as rhizobial infection and the nitrate application as well as various internal stimuli. To investigate whether LjCLE gene(s) may involve in plant response to inorganic phosphate (Pi), we analyzed Pi responses of 39 LjCLE genes in hydroponically grown Lotus japonicus plants (ecotype Miyakojima 'MG-20'). Two LjCLE genes, LjCLE19 and 20, were up-regulated specifically and greatly in roots of L. japonicus by Pi addition to the hydroponic solution. When the external Pi level increased, expressions of LjCLE19 and 20 increased before the increase in the Pi content in plants. On the other hand, when the external Pi level decreased, the Pi content in plants decreased first, then expression levels of LjCLE19 and 20 decreased. Based on our results, we discuss the relationship between LjCLE19 and 20 and the tissue Pi levels in plants. This is the first report showing induction of specific CLE genes by phosphate.