Expression of EuNOD-ARP1 encoding auxin-repressed protein homolog is upregulated by auxin and localized to the fixation zone in root nodules of Elaeagnus umbellata.
Root nodule formation is controlled by plant hormones such as auxin. Auxin-repressed protein (ARP) genes have been identified in various plant species but their functions are not clear. We have isolated a full-length cDNA clone (EuNOD-ARP1) showing high sequence homology to previously identified ARP genes from root nodules of Elaeagnus umbellata. Genomic Southern hybridization showed that there are at least four ARP-related genes in the genome of E. umbellata. The cDNA clone encodes a polypeptide of 120 amino acid residues with no signal peptide or organelle-targeting signals, indicating that it is a cytosolic protein. Its cytosolic location was confirmed using Arabidopsis protoplasts expressing a EuNOD-ARP1:smGFP fusion protein. Northern hybridization showed that EuNOD-ARP1 expression was higher in root nodules than in leaves or uninoculated roots. Unlike the ARP genes of strawberry and black locust, which are negatively regulated by exogenous auxin, EuNOD-ARP1 expression is induced by auxin in leaf tissue of E. umbellata. In situ hybridization revealed that EuNOD-ARP1 is mainly expressed in the fixation zone of root nodules.
Kim
Ho Bang
HB
School of Biological Sciences, College of Natural Sciences, Seoul National University, Seoul 151-747, Korea. hobang@snu.ac.kr
Lee
Hyoungseok
H
Oh
Chang Jae
CJ
Lee
Nam Houn
NH
An
Chung Sun
CS
D000595:Amino Acid Sequence; D015139:Blotting, Southern; D031263:Elaeagnaceae / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D018745:Genome, Plant / Q000187:drug effects; D007210:Indoleacetic Acids / Q000494:pharmacology*; D008969:Molecular Sequence Data; D005810:Multigene Family; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D053204:Root Nodules, Plant / Q000166:cytology / Q000187:drug effects*; D017386:Sequence Homology, Amino Acid; D015854:Up-Regulation / Q000187:drug effects*
D007210:Indoleacetic Acids; D010940:Plant Proteins; D012333:RNA, Messenger