Abstract
Nitrate inhibits Rhizobium-Legume symbiosis in processes of rhizobial infection into root hairs. To elucidate the nitrate-induced inhibition in early infection events during nodulation, we screened the transcriptional response of 19,000 genes in root hairs of Lotus japonicus. Results showed that after 4 days treatment of root hairs with nitrate, in addition to nitrogen assimilation related genes, novel nitrate inducible genes encoding HPP domain containing protein, MYB-type transcription factor, and leucine rich repeat protein were identified. Interestingly, genes encoding 12-oxo-phytodienoic acid reductase, glutathione S-transferase, and UDP-glucosyltransferase known as jasmonic acid (JA) inducible genes were reduced. Application of exogenous JA to Rhizobium infection assay showed that infection thread formation was enhanced remarkably in growth condition without nitrate. Our data indicate that decreasing accumulation of JA caused by nitrate might induce salicylic acid related defense responses on rhizobial infection process in root hairs.
