title: Abscisic acid promotes proteasome-mediated degradation of the transcription coactivator NPR1 in Arabidopsis thaliana.
abstract: Proteasome-mediated turnover of the transcription coactivator NPR1 is pivotal for efficient activation of the broad-spectrum plant immune responses known as localized acquired resistance (LAR) and systemic acquired resistance (SAR) in adjacent and systemic tissues, respectively, and requires the CUL3-based E3 ligase and its adaptor proteins, NPR3 and NPR4, which are receptors for the signaling molecule salicylic acid (SA). It has been shown that SA prevents NPR1 turnover under non-inducing and LAR/SAR-inducing conditions, but how cellular NPR1 homeostasis is maintained remains unclear. Here, we show that the phytohormone abscisic acid (ABA) and SA antagonistically influence cellular NPR1 protein levels. ABA promotes NPR1 degradation via the CUL3(NPR) (3/) (NPR) (4) complex-mediated proteasome pathway, whereas SA may protect NPR1 from ABA-promoted degradation through phosphorylation. Furthermore, we demonstrate that the timing and strength of SA and ABA signaling are critical in modulating NPR1 accumulation and target gene expression. Perturbing ABA or SA signaling in adjacent tissues alters the temporal dynamic pattern of NPR1 accumulation and target gene transcription. Finally, we show that sequential SA and ABA treatment leads to dynamic changes in NPR1 protein levels and target gene expression. Our results revealed a tight correlation between sequential SA and ABA signaling and dynamic changes in NPR1 protein levels and NPR1-dependent transcription in plant immune responses.
authors: Department of Microbiology and Cell Science, University of Florida, PO Box 110700, Gainesville, FL 32611, USA.
authors: Yezhang
authors: Y
authors: Ding
authors: Department of Microbiology and Cell Science, University of Florida, PO Box 110700, Gainesville, FL 32611, USA.
authors: Matthew
authors: M
authors: Dommel
authors: Department of Microbiology and Cell Science, University of Florida, PO Box 110700, Gainesville, FL 32611, USA.
authors: Zhonglin
authors: Z
authors: Mou
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D006706:Homeostasis; D010766:Phosphorylation; D010937:Plant Growth Regulators / Q000378:metabolism*; D057865:Plant Immunity; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D020156:Salicylic Acid / Q000378:metabolism; D015398:Signal Transduction; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C105496:NPR1 protein, Arabidopsis; C517740:NPR3 protein, Arabidopsis; C502134:NPR4 protein, Arabidopsis; D010937:Plant Growth Regulators; D000040:Abscisic Acid; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex; D020156:Salicylic Acid
keywords: Arabidopsis thaliana; NPR1; abscisic acid; plant immunity; protein degradation; salicylic acid