title: Identification of Methylosome Components as Negative Regulators of Plant Immunity Using Chemical Genetics.
abstract: Nucleotide-binding leucine-rich repeat (NLR) proteins serve as immune receptors in both plants and animals. To identify components required for NLR-mediated immunity, we designed and carried out a chemical genetics screen to search for small molecules that can alter immune responses in Arabidopsis thaliana. From 13 600 compounds, we identified Ro 8-4304 that was able to specifically suppress the severe autoimmune phenotypes of chs3-2D (chilling sensitive 3, 2D), including the arrested growth morphology and heightened PR (Pathogenesis Related) gene expression. Further, six Ro 8-4304 insensitive mutants were uncovered from the Ro 8-4304-insensitive mutant (rim) screen using a mutagenized chs3-2D population. Positional cloning revealed that rim1 encodes an allele of AtICln (I, currents; Cl, chloride; n, nucleotide). Genetic and biochemical analysis demonstrated that AtICln is in the same protein complex with the methylosome components small nuclear ribonucleoprotein D3b (SmD3b) and protein arginine methyltransferase 5 (PRMT5), which are required for the biogenesis of small nuclear ribonucleoproteins (snRNPs) involved in mRNA splicing. Double mutant analysis revealed that SmD3b is also involved in the sensitivity to Ro 8-4304, and the prmt5-1 chs3-2D double mutant is lethal. Loss of AtICln, SmD3b, or PRMT5 function results in enhanced disease resistance against the virulent oomycete pathogen Hyaloperonospora arabidopsidis Noco2, suggesting that mRNA splicing plays a previously unknown negative role in plant immunity. The successful implementation of a high-throughput chemical genetic screen and the identification of a small-molecule compound affecting plant immunity indicate that chemical genetics is a powerful tool to study whole-organism plant defense pathways.
authors.affiliation: Michael Smith Laboratories, University of British Columbia, Vancouver, BC V6T 1Z4, Canada; Department of Botany, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
authors.forename: Shuai
authors.initials: S
authors.lastname: Huang
authors.affiliation: Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC V6T 1Z3, Canada.
authors.forename: Aruna
authors.initials: A
authors.lastname: Balgi
authors.affiliation: Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: Yaping
authors.initials: Y
authors.lastname: Pan
authors.affiliation: Department of Botany, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
authors.forename: Meng
authors.initials: M
authors.lastname: Li
authors.affiliation: National Institute of Biological Sciences, Beijing 102206, China.
authors.forename: Xiaoran
authors.initials: X
authors.lastname: Zhang
authors.affiliation: National Institute of Biological Sciences, Beijing 102206, China.
authors.forename: Lilin
authors.initials: L
authors.lastname: Du
authors.affiliation: Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: Ming
authors.initials: M
authors.lastname: Zhou
authors.affiliation: Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC V6T 1Z3, Canada.
authors.forename: Michel
authors.initials: M
authors.lastname: Roberge
authors.affiliation: Michael Smith Laboratories, University of British Columbia, Vancouver, BC V6T 1Z4, Canada; Department of Botany, University of British Columbia, Vancouver, BC V6T 1Z4, Canada. Electronic address: xinli@msl.ubc.ca.
authors.forename: Xin
authors.initials: X
authors.lastname: Li
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D015551:Autoimmunity / Q000235:genetics / Q000502:physiology; D060467:Disease Resistance / Q000235:genetics / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D057865:Plant Immunity / Q000235:genetics / Q000502:physiology*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D011484:Protein-Arginine N-Methyltransferases / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D011484:Protein-Arginine N-Methyltransferases
keywords: TNL; autoimmunity; chemical genetics; methylosome; plant immunity; small molecule screening