Lotus japonicus NLP1 and NLP4 transcription factors have different roles in the regulation of nitrate transporter family gene expression

Root nodule symbiosis is promoted in nitrogen-deficient environments, whereas host plants cease the symbiosis if they can obtain enough nitrogen from their surrounding soil. In Lotus japonicus, recent reports indicate that two NODULE INCEPTION (NIN)-LIKE PROTEIN (NLP) transcription factors, LjNLP1 and LjNLP4, play important roles in the regulation of gene expression and nodulation in response to nitrate. To characterize the redundant and unique roles of LjNLP1 and LjNLP4 in more detail, we reanalyzed our previous transcriptome data using Ljnlp1 and Ljnlp4 mutants. Although downstream genes of LjNLP1 and LjNLP4 mostly overlapped, we found that nitrate-induced expression of NITRATE TRANSPORTER 2 (LjNRT2) family genes was specifically regulated by LjNLP1. In contrast, LjNRT1 gene family expression was regulated by both LjNLP1 and LjNLP4. Therefore, it is likely that the two NLPs play distinct roles in the regulation of nitrate transport.

Automated summary

Root nodule symbiosis is influenced by nitrogen availability and Lotus japonicus NODULE INCEPTION (NIN)-LIKE PROTEIN (NLP) transcription factors LjNLP1 and LjNLP4 play important roles in gene regulation and nodulation response to nitrate. LjNLP1 specifically regulates the expression of the NITRATE TRANSPORTER 2 (LjNRT2) gene family, while both LjNLP1 and LjNLP4 regulate the expression of the LjNRT1 gene family, suggesting distinct functions in nitrate transport regulation.