The salicylic acid receptor NPR3 is a negative regulator of the transcriptional defense response during early flower development in Arabidopsis.
Arabidopsis non-expressor of PR1 (NPR1) is a transcription co-activator that plays a central role in regulating the transcriptional response to plant pathogens. The NPR family consists of NPR1 and five NPR1-like genes. The NPR1 paralog NPR3 has recently been shown to function as a receptor of the plant hormone salicylic acid and to mediate proteosomal degradation of NPR1. The function of NPR3 protein during early flower development was revealed through a detailed molecular-genetic analysis including promoter transcriptional fusion analysis, phenotype characterization of npr3-3 mutants/overexpressors, and whole-plant fitness analysis. The physical interaction between NPR3 and NPR1/TGA2 was explored using bimolecular fluorescence complementation analysis in onion epidermal cells. Here, we show that NPR3 expression was strongest in the petals and sepals of developing flowers and declined after flower opening. Consistently with this observation, an npr3 knockout mutant displayed enhanced resistance to Pseudomonas syringae infection of immature flowers, but not leaves. Developing npr3 flowers exhibited increased levels of basal and induced PR1 transcript accumulation. However, the npr3 mutant showed lower fitness compared to Col-0 in the absence of pathogen. Moreover, NPR3 was shown to interact with NPR1 and TGA2 in vivo. Our data suggest that NPR3 is a negative regulator of defense responses during early flower development and it may function through the association with both NPR1 and TGA2.
['Shi|Zi|Z|', 'Maximova|Siela|S|', 'Liu|Yi|Y|', 'Verica|Joseph|J|', 'Guiltinan|Mark J|MJ|']
D017360:Arabidopsis D029681:Arabidopsis Proteins D060467:Disease Resistance D035264:Flowers D005453:Fluorescence D020869:Gene Expression Profiling D018506:Gene Expression Regulation, Plant D005799:Genes, Dominant D017343:Genes, Plant D049452:Green Fluorescent Proteins D009154:Mutation D010802:Phylogeny D010935:Plant Diseases D030821:Plants, Genetically Modified D011401:Promoter Regions, Genetic D011485:Protein Binding D044224:Pseudomonas syringae D012097:Repressor Proteins D020156:Salicylic Acid D015398:Signal Transduction D014158:Transcription, Genetic
NPR3 negative regulator flower Arabidopsis plant defense