title: Rice NRR, a negative regulator of disease resistance, interacts with Arabidopsis NPR1 and rice NH1.
abstract: Arabidopsis NPR1/NIM1 is a key regulator of systemic acquired resistance (SAR), which confers lasting broad-spectrum resistance. Over-expression of Arabidopsis NPR1 or the NPR1 homolog 1 (NH1) in rice results in enhanced resistance to the pathogen Xanthomonasoryzae pv. oryzae (Xoo), suggesting the presence of a related defense pathway in rice. We investigated this pathway in rice by identifying proteins that interact with NH1. Here we report the isolation and characterization of a rice cDNA encoding a novel protein, named NRR (for negative regulator of resistance). NRR interacts with NPR1 in the NPR1-interacting domain (NI25) consisting of 25 amino acids. NRR also interacts with NH1; however, NI25 was not sufficient for a strong interaction, indicating a difference between the rice and the Arabidopsis proteins. Silencing of NRR in rice had little effect on resistance to Xoo. When constitutively over-expressed in rice, NRR affected basal resistance, age-related resistance and Xa21-mediated resistance, causing enhanced susceptibility to Xoo. This phenotype was correlated with elevated NRR mRNA and protein levels and increased Xoo growth. Over-expression of NRR suppressed the induction of defense-related genes. NRR:GFP (green fluorescent protein) protein was localized to the nucleus, indicating that NRR may act directly to suppress the activation of defense genes. The fact that NRR compromises Xa21-mediated resistance indicates cross-talk or overlap between NH1- and Xa21-mediated pathways.
authors.affiliation: Department of Plant Pathology, University of California, Davis, CA 95616, USA.
authors.forename: Mawsheng
authors.initials: M
authors.lastname: Chern
authors.forename: Patrick E
authors.initials: PE
authors.lastname: Canlas
authors.forename: Heather A
authors.initials: HA
authors.lastname: Fitzgerald
authors.forename: Pamela C
authors.initials: PC
authors.lastname: Ronald
mesh_terms: D000595:Amino Acid Sequence; D029681:Arabidopsis Proteins / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000276:immunology*; D020868:Gene Silencing; D007113:Immunity, Innate / Q000235:genetics; D008969:Molecular Sequence Data; D012275:Oryza / Q000235:genetics / Q000378:metabolism*; D010935:Plant Diseases / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D012333:RNA, Messenger / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013997:Time Factors; D020798:Two-Hybrid System Techniques; D014974:Xanthomonas / Q000502:physiology
chemical_list: D029681:Arabidopsis Proteins; C105496:NPR1 protein, Arabidopsis; D010940:Plant Proteins; D012333:RNA, Messenger