Non-recognition-of-BTH4, an Arabidopsis mediator subunit homolog, is necessary for development and response to salicylic acid.
Salicylic acid (SA) signaling acts in defense and plant development. The only gene demonstrated to be required for the response to SA is Arabidopsis thaliana non-expresser of pathogenesis-related gene 1 (NPR1), and npr1 mutants are insensitive to SA. By focusing on the effect of analogs of SA on plant development, we identified mutants in additional genes acting in the SA response. In this work, we describe a gene necessary for the SA Non-Recognition-of-BTH4 (NRB4). Three nrb4 alleles recovered from the screen cause phenotypes similar to the wild type in the tested conditions, except for SA-related phenotypes. Plants with NRB4 null alleles express profound insensitivity to SA, even more than npr1. NRB4 null mutants are also sterile and their growth is compromised. Plants carrying weaker nrb4 alleles are also insensitive to SA, with some quantitative differences in some phenotypes, like systemic acquired resistance or pathogen growth restriction. When weak alleles are used, NPR1 and NRB4 mutations produce an additive phenotype, but we did not find evidence of a genetic interaction in F1 nor biochemical interaction in yeast or in planta. NRB4 is predicted to be a subunit of Mediator, the ortholog of MED15 in Arabidopsis. Mechanistically, NRB4 functions downstream of NPR1 to regulate the SA response.
Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Ciudad Politécnica de la Inovación, 46022 Valencia, Spain.
Juan Vicente
JV
Canet
Albor
A
Dobón
Pablo
P
Tornero
D000483:Alleles; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D003001:Cloning, Molecular; D020869:Gene Expression Profiling; D047908:Intracellular Signaling Peptides and Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D056892:Mediator Complex / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D010641:Phenotype; D025941:Protein Interaction Mapping; D020156:Salicylic Acid / Q000494:pharmacology*; D015398:Signal Transduction
D029681:Arabidopsis Proteins; D047908:Intracellular Signaling Peptides and Proteins; D056892:Mediator Complex; C105496:NPR1 protein, Arabidopsis; C581741:NRB4 protein, Arabidopsis; D020156:Salicylic Acid