title: Differential Roles of Two Homologous Cyclin-Dependent Kinase Inhibitor Genes in Regulating Cell Cycle and Innate Immunity in Arabidopsis.
abstract: Precise cell-cycle control is critical for plant development and responses to pathogen invasion. Two homologous cyclin-dependent kinase inhibitor genes, SIAMESE (SIM) and SIM-RELATED 1 (SMR1), were recently shown to regulate Arabidopsis (Arabidopsis thaliana) defense based on phenotypes conferred by a sim smr1 double mutant. However, whether these two genes play differential roles in cell-cycle and defense control is unknown. In this report, we show that while acting synergistically to promote endoreplication, SIM and SMR1 play different roles in affecting the ploidy of trichome and leaf cells, respectively. In addition, we found that the smr1-1 mutant, but not sim-1, was more susceptible to a virulent Pseudomonas syringae strain, and this susceptibility could be rescued by activating salicylic acid (SA)-mediated defense. Consistent with these results, smr1-1 partially suppressed the dwarfism, high SA levels, and cell death phenotypes in acd6-1, a mutant used to gauge the change of defense levels. Thus, SMR1 functions partly through SA in defense control. The differential roles of SIM and SMR1 are due to differences in temporal and spatial expression of these two genes in Arabidopsis tissues and in response to P. syringae infection. In addition, flow-cytometry analysis of plants with altered SA signaling revealed that SA is necessary, but not sufficient, to change cell-cycle progression. We further found that a mutant with three CYCD3 genes disrupted also compromised disease resistance to P. syringae. Together, this study reveals differential roles of two homologous cyclin-dependent kinase inhibitors in regulating cell-cycle progression and innate immunity in Arabidopsis and provides insights into the importance of cell-cycle control during host-pathogen interactions.
authors.affiliation: Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, Maryland 21250 (S.H., C.Z., M.G., A.K., H.L.); andDepartment of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803 (N.K., M.C., J.C.L.).
authors.forename: Safae
authors.initials: S
authors.lastname: Hamdoun
authors.affiliation: Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, Maryland 21250 (S.H., C.Z., M.G., A.K., H.L.); andDepartment of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803 (N.K., M.C., J.C.L.).
authors.forename: Chong
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, Maryland 21250 (S.H., C.Z., M.G., A.K., H.L.); andDepartment of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803 (N.K., M.C., J.C.L.).
authors.forename: Manroop
authors.initials: M
authors.lastname: Gill
authors.affiliation: Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, Maryland 21250 (S.H., C.Z., M.G., A.K., H.L.); andDepartment of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803 (N.K., M.C., J.C.L.).
authors.forename: Narender
authors.identifier: http://orcid.org/0000-0002-2009-3158
authors.initials: N
authors.lastname: Kumar
authors.affiliation: Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, Maryland 21250 (S.H., C.Z., M.G., A.K., H.L.); andDepartment of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803 (N.K., M.C., J.C.L.).
authors.forename: Michelle
authors.initials: M
authors.lastname: Churchman
authors.affiliation: Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, Maryland 21250 (S.H., C.Z., M.G., A.K., H.L.); andDepartment of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803 (N.K., M.C., J.C.L.).
authors.forename: John C
authors.initials: JC
authors.lastname: Larkin
authors.affiliation: Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, Maryland 21250 (S.H., C.Z., M.G., A.K., H.L.); andDepartment of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803 (N.K., M.C., J.C.L.).
authors.forename: Ashley
authors.identifier: http://orcid.org/0000-0001-9635-7482
authors.initials: A
authors.lastname: Kwon
authors.affiliation: Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, Maryland 21250 (S.H., C.Z., M.G., A.K., H.L.); andDepartment of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803 (N.K., M.C., J.C.L.) hualu@umbc.edu.
authors.forename: Hua
authors.identifier: http://orcid.org/0000-0002-7496-3200
authors.initials: H
authors.lastname: Lu
mesh_terms: D017360:Arabidopsis / Q000166:cytology* / Q000276:immunology* / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D002453:Cell Cycle / Q000235:genetics; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D016213:Cyclins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D060467:Disease Resistance / Q000235:genetics / Q000276:immunology; D018506:Gene Expression Regulation, Plant; D054884:Host-Pathogen Interactions / Q000235:genetics; D007113:Immunity, Innate / Q000235:genetics*; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D010935:Plant Diseases / Q000382:microbiology; D018515:Plant Leaves / Q000235:genetics; D030821:Plants, Genetically Modified; D011003:Ploidies; D044224:Pseudomonas syringae / Q000472:pathogenicity; D020156:Salicylic Acid / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C000610876:At3g10525 protein, Arabidopsis; D018797:Cell Cycle Proteins; C496944:CycD3 protein, Arabidopsis; D016213:Cyclins; D009687:Nuclear Proteins; C517317:SIAMESE protein, Arabidopsis; D020156:Salicylic Acid