1. NLR-associating transcription factor bHLH84 and its paralogs function redundantly in plant immunity
- Author
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Fang Xu, Meng Li, Paul Kapos, Yu Ti Cheng, Yuelin Zhang, and Xin Li
- Subjects
lcsh:Immunologic diseases. Allergy ,Immunology ,Mutant ,Arabidopsis ,Repressor ,Biology ,medicine.disease_cause ,Microbiology ,NLR Proteins ,Gene Knockout Techniques ,Gene Expression Regulation, Plant ,Virology ,Genetics ,medicine ,Transcriptional regulation ,Immunoprecipitation ,Plant Immunity ,Molecular Biology ,Transcription factor ,lcsh:QH301-705.5 ,Regulation of gene expression ,Mutation ,Microscopy, Confocal ,Arabidopsis Proteins ,Reverse Transcriptase Polymerase Chain Reaction ,fungi ,Biology and Life Sciences ,Plants, Genetically Modified ,lcsh:Biology (General) ,Parasitology ,lcsh:RC581-607 ,Transcription Factors ,Research Article ,Genetic screen - Abstract
In plants and animals, nucleotide-binding and leucine-rich repeat domain containing (NLR) immune receptors are utilized to detect the presence or activities of pathogen-derived molecules. However, the mechanisms by which NLR proteins induce defense responses remain unclear. Here, we report the characterization of one basic Helix-loop-Helix (bHLH) type transcription factor (TF), bHLH84, identified from a reverse genetic screen. It functions as a transcriptional activator that enhances the autoimmunity of NLR mutant snc1 (suppressor of npr1-1, constitutive 1) and confers enhanced immunity in wild-type backgrounds when overexpressed. Simultaneously knocking out three closely related bHLH paralogs attenuates RPS4-mediated immunity and partially suppresses the autoimmune phenotypes of snc1, while overexpression of the other two close paralogs also renders strong autoimmunity, suggesting functional redundancy in the gene family. Intriguingly, the autoimmunity conferred by bHLH84 overexpression can be largely suppressed by the loss-of-function snc1-r1 mutation, suggesting that SNC1 is required for its proper function. In planta co-immunoprecipitation revealed interactions between not only bHLH84 and SNC1, but also bHLH84 and RPS4, indicating that bHLH84 associates with these NLRs. Together with previous finding that SNC1 associates with repressor TPR1 to repress negative regulators, we hypothesize that nuclear NLR proteins may interact with both transcriptional repressors and activators during immune responses, enabling potentially faster and more robust transcriptional reprogramming upon pathogen recognition., Author Summary In plants and animals, NLR immune receptors are utilized to detect pathogen-derived molecules and activate immunity. However, the mechanisms of plant NLR activation remain unclear. Here, we report on bHLH84, which functions as a transcriptional activator. Simultaneously knocking out three closely related bHLH paralogs partially suppresses the autoimmunity of snc1 and compromises RPS4-mediated defense, while overexpression of these close paralogs renders strong autoimmunity, suggesting functional redundancy in the gene family. In planta co-immunoprecipitation revealed interactions between not only bHLH84 and SNC1, but also bHLH84 and RPS4. Therefore bHLH84 family transcription factors associate with these NLRs to activate defense responses, enabling potentially faster and more robust transcriptional reprogramming upon pathogen recognition.
- Published
- 2014