title: Novel functions of Stomatal Cytokinesis-Defective 1 (SCD1) in innate immune responses against bacteria.
abstract: Eukaryotes employ complex immune mechanisms for protection against microbial pathogens. Here, we identified SCD1 (Stomatal Cytokinesis-Defective 1), previously implicated in growth and development through its role in cytokinesis and polarized cell expansion (Falbel, T. G., Koch, L. M., Nadeau, J. A., Segui-Simarro, J. M., Sack, F. D., and Bednarek, S. Y. (2003) Development 130, 4011-4024) as a novel component of innate immunity. In Arabidopsis, SCD1 is a unique gene encoding for the only protein containing a complete DENN (Differentially Expressed in Normal and Neoplastic cells) domain. The DENN domain is a largely uncharacterized tripartite protein motif conserved among eukaryotic proteins. We show that conditional scd1-1 plants containing a point mutation in a conserved DENN residue affected a subset of signaling responses to some bacterial pathogen-associated molecular patterns (PAMPs). Consistent with increased transcript accumulation of Pathogen-related (PR) genes, scd1-1 plants were more resistant to Pseudomonas syringae pathovar tomato (Pst) DC3000 infection implicating SCD1 as a negative regulator of basal resistance against bacteria. scd1-1 plants were different from known mutants exhibiting constitutive expressor of PR (cpr)-like phenotypes, in that growth impairment of scd1-1 plants was genetically independent of constitutive immune response activation. For scd1-1, shift to elevated temperature or introduction of a mutant allele in Salicylic acid Induction-Deficient 2 (SID2) suppressed constitutive defense response activation. sid2-2 also repressed the resistance phenotype of scd1-1. Temperature shift and sid2-2, however, did not rescue conditional growth and sterility defects of scd1-1. These results implicate SCD1 in multiple cellular pathways, possibly by affecting different proteins. Overall, our studies identified a novel role for eukaryotic DENN proteins in immunity against bacteria.
authors.affiliation: Interdisciplinary Plant Group (IPG), Division of Biochemistry, University of Missouri-Columbia, Columbia, Missouri 65211, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Korasick
authors.forename: Colleen
authors.initials: C
authors.lastname: McMichael
authors.forename: Katie A
authors.initials: KA
authors.lastname: Walker
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Anderson
authors.forename: Sebastian Y
authors.initials: SY
authors.lastname: Bednarek
authors.forename: Antje
authors.initials: A
authors.lastname: Heese
mesh_terms: D016960:Agrobacterium tumefaciens / Q000502:physiology; D000595:Amino Acid Sequence; D018407:Bacterial Physiological Phenomena; D017353:Gene Deletion; D007113:Immunity, Innate; D008969:Molecular Sequence Data; D010641:Phenotype; D063245:Plant Development; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D054046:Plant Stomata / Q000254:growth & development / Q000276:immunology* / Q000378:metabolism* / Q000382:microbiology; D010944:Plants / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology*; D017434:Protein Structure, Tertiary; D011550:Pseudomonas aeruginosa / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism; D013696:Temperature
chemical_list: D010940:Plant Proteins; D017382:Reactive Oxygen Species
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