title: Pepper arginine decarboxylase is required for polyamine and γ-aminobutyric acid signaling in cell death and defense response.
abstract: The Xanthomonas campestris pv vesicatoria (Xcv) effector AvrBsT induces a hypersensitive cell death in pepper (Capsicum annuum). However, the molecular mechanisms underlying AvrBsT-triggered cell death are not fully understood. Here, we identified pepper arginine decarboxylase (CaADC1) as an AvrBsT-interacting protein, which is early and strongly induced in incompatible pepper-Xcv interactions. Bimolecular fluorescence complementation and coimmunoprecipitation assays showed that the CaADC1-AvrBsT complex was localized to the cytoplasm. Transient coexpression of CaADC1 with avrBsT in Nicotiana benthamiana leaves specifically enhanced AvrBsT-triggered cell death, accompanied by an accumulation of polyamines, nitric oxide (NO), and hydrogen peroxide (H₂O₂) bursts. Among the polyamines, spermine application strongly induced NO and H₂O₂ bursts, ultimately leading to cell death. CaADC1 silencing in pepper leaves significantly compromised NO and H₂O₂ accumulation and cell death induction, leading to the enhanced avirulent Xcv growth during infection. The levels of salicylic acid, polyamines, and γ-aminobutyric acid (GABA), and the expression of defense response genes during avirulent Xcv infection, were distinctly lower in CaADC1-silenced plants than those in the empty vector control plants. GABA application significantly inhibited avirulent Xcv growth in CaADC1-silenced leaves and the empty vector control plants. Together, these results suggest that CaADC1 may act as a key defense and cell death regulator via mediation of polyamine and GABA metabolism.
authors.affiliation: College of Life Sciences and Biotechnology, Korea University, Seoul 136-713, Republic of Korea.
authors.forename: Nak Hyun
authors.initials: NH
authors.lastname: Kim
authors.forename: Beom Seok
authors.initials: BS
authors.lastname: Kim
authors.forename: Byung Kook
authors.initials: BK
authors.lastname: Hwang
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D002212:Capsicum / Q000187:drug effects / Q000382:microbiology / Q000502:physiology*; D002262:Carboxy-Lyases / Q000235:genetics / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects; D018506:Gene Expression Regulation, Plant; D054884:Host-Pathogen Interactions / Q000502:physiology; D006861:Hydrogen Peroxide / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D018515:Plant Leaves / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011073:Polyamines / Q000378:metabolism*; D015398:Signal Transduction; D013096:Spermine / Q000378:metabolism / Q000494:pharmacology; D014026:Nicotiana / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D016959:Xanthomonas campestris / Q000472:pathogenicity; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D010940:Plant Proteins; D011073:Polyamines; D013096:Spermine; D009569:Nitric Oxide; D005680:gamma-Aminobutyric Acid; D006861:Hydrogen Peroxide; D002262:Carboxy-Lyases; C019722:arginine decarboxylase