A positive regulatory role for LjERF1 in the nodulation process is revealed by systematic analysis of nodule-associated transcription factors of Lotus japonicus.
We have used reverse genetics to identify genes involved in legume-rhizobium symbiosis in Lotus japonicus. We obtained the sequences of 20 putative transcription factors from previously reported large-scale transcriptome data. The transcription factors were classified according to their DNA binding domains and patterns of expression during the nodulation process. We identified two homologues of Medicago truncatula MtHAP2-1, which encodes a CCAAT-binding protein and has been shown to play a role in nodulation. The functions of the remaining genes in the nodulation process have not been reported. Seven genes were found to encode proteins with AP2-EREBP domains, six of which were similar to proteins that have been implicated in ethylene and/or jasmonic acid signal transduction and defense gene regulation in Arabidopsis (Arabidopsis thaliana). We identified a gene, LjERF1, that is most similar to Arabidopsis ERF1, which is up-regulated by ethylene and jasmonic acid and activates downstream defense genes. LjERF1 showed the same pattern of up-regulation in roots as Arabidopsis ERF1. The nodulation phenotype of roots that overexpressed LjERF1 or inhibited LjERF1 expression using an RNA interference construct indicated that this gene functions as a positive regulator of nodulation. We propose that LjERF1 functions as a key regulator of successful infection of L. japonicus by Mesorhizobium loti.
Department of Plant Genome Research, Kazusa DNA Research Institute, Kisarazu, Chiba 292-0818, Japan. asamizu@gene.tsukuba.ac.jp
Erika
E
Asamizu
Yoshikazu
Y
Shimoda
Hiroshi
H
Kouchi
Satoshi
S
Tabata
Shusei
S
Sato
D001483:Base Sequence; D003517:Cyclopentanes / Q000494:pharmacology; D005030:Ethylenes / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D000070116:Lotus / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology; D046913:Medicago truncatula / Q000502:physiology; D008969:Molecular Sequence Data; D005810:Multigene Family; D020411:Oligonucleotide Array Sequence Analysis; D054883:Oxylipins / Q000494:pharmacology; D010454:Peptide Termination Factors / Q000032:analysis / Q000737:chemistry / Q000502:physiology*; D010802:Phylogeny; D010940:Plant Proteins / Q000032:analysis / Q000737:chemistry / Q000502:physiology*; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D053204:Root Nodules, Plant / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D014157:Transcription Factors / Q000032:analysis / Q000737:chemistry / Q000502:physiology; D015854:Up-Regulation
D003517:Cyclopentanes; D005030:Ethylenes; D054883:Oxylipins; D010454:Peptide Termination Factors; D010940:Plant Proteins; D014157:Transcription Factors; C011006:jasmonic acid; C036216:ethylene