title: Arabidopsis sigma factor binding proteins are activators of the WRKY33 transcription factor in plant defense.
abstract: Necrotrophic pathogens are important plant pathogens that cause many devastating plant diseases. Despite their impact, our understanding of the plant defense response to necrotrophic pathogens is limited. The WRKY33 transcription factor is important for plant resistance to necrotrophic pathogens; therefore, elucidation of its functions will enhance our understanding of plant immunity to necrotrophic pathogens. Here, we report the identification of two WRKY33-interacting proteins, nuclear-encoded SIGMA FACTOR BINDING PROTEIN1 (SIB1) and SIB2, which also interact with plastid-encoded plastid RNA polymerase SIGMA FACTOR1. Both SIB1 and SIB2 contain an N-terminal chloroplast targeting signal and a putative nuclear localization signal, suggesting that they are dual targeted. Bimolecular fluorescence complementation indicates that WRKY33 interacts with SIBs in the nucleus of plant cells. Both SIB1 and SIB2 contain a short VQ motif that is important for interaction with WRKY33. The two VQ motif-containing proteins recognize the C-terminal WRKY domain and stimulate the DNA binding activity of WRKY33. Like WRKY33, both SIB1 and SIB2 are rapidly and strongly induced by the necrotrophic pathogen Botrytis cinerea. Resistance to B. cinerea is compromised in the sib1 and sib2 mutants but enhanced in SIB1-overexpressing transgenic plants. These results suggest that dual-targeted SIB1 and SIB2 function as activators of WRKY33 in plant defense against necrotrophic pathogens.
authors: Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana 47907-2054, USA.
authors: Zhibing
authors: Z
authors: Lai
authors: Ying
authors: Y
authors: Li
authors: Fei
authors: F
authors: Wang
authors: Yuan
authors: Y
authors: Cheng
authors: Baofang
authors: B
authors: Fan
authors: Jing-Quan
authors: JQ
authors: Yu
authors: Zhixiang
authors: Z
authors: Chen
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000276:immunology* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D020171:Botrytis / Q000276:immunology / Q000472:pathogenicity*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D018744:DNA, Plant / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology; D030821:Plants, Genetically Modified; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins; D016415:Sequence Alignment; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D018744:DNA, Plant; D011993:Recombinant Fusion Proteins; C453496:SIB1 protein, Arabidopsis; C573055:SIB2 protein, Arabidopsis; D012808:Sigma Factor; D014157:Transcription Factors; C517860:WRKY33 protein, Arabidopsis; D003577:Cytochrome P-450 Enzyme System; C417307:PAD3 protein, Arabidopsis