title: An important role of the pepper phenylalanine ammonia-lyase gene (PAL1) in salicylic acid-dependent signalling of the defence response to microbial pathogens.
abstract: Phenylalanine ammonia-lyase (PAL) has a crucial role in secondary phenylpropanoid metabolism and is one of the most extensively studied enzymes with respect to plant responses to biotic and abiotic stress. Here, we identified the pepper (Capsicum annuum) PAL (CaPAL1) gene, which was induced in pepper leaves by avirulent Xanthomonas campestris pv. vesicatoria (Xcv) infection. CaPAL1-silenced pepper plants exhibited increased susceptibility to virulent and avirulent Xcv infection. Reactive oxygen species (ROS), hypersensitive cell death, expression of the salicylic acid (SA)-dependent marker gene CaPR1, SA accumulation, and induction of PAL activity were significantly compromised in the CaPAL1-silenced pepper plants during Xcv infection. Overexpression (OX) of CaPAL1 in Arabidopsis conferred increased resistance to Pseudomonas syringae pv. tomato (Pst) and Hyaloperonospora arabidopsidis infection. CaPAL1-OX leaves exhibited restricted Pst growth, increased ROS burst and cell death, and induction of PR1 expression and SA accumulation. The increase in PAL activity in healthy and Pst-infected leaves was higher in CaPAL1-OX plants than in wild-type Arabidopsis. Taken together, these results suggest that CaPAL1 acts as a positive regulator of SA-dependent defence signalling to combat microbial pathogens via its enzymatic activity in the phenylpropanoid pathway.
authors.affiliation: Laboratory of Molecular Plant Pathology, College of Life Sciences and Biotechnology, Korea University, Anam-dong, Sungbuk-ku, Seoul 136-713, Republic of Korea.
authors.forename: Dae Sung
authors.initials: DS
authors.lastname: Kim
authors.affiliation: Laboratory of Molecular Plant Pathology, College of Life Sciences and Biotechnology, Korea University, Anam-dong, Sungbuk-ku, Seoul 136-713, Republic of Korea bkhwang@korea.ac.kr.
authors.forename: Byung Kook
authors.initials: BK
authors.lastname: Hwang
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D002212:Capsicum / Q000201:enzymology* / Q000235:genetics; D060467:Disease Resistance; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D054884:Host-Pathogen Interactions; D010650:Phenylalanine Ammonia-Lyase / Q000235:genetics / Q000378:metabolism*; D010935:Plant Diseases / Q000276:immunology / Q000382:microbiology*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D044224:Pseudomonas syringae / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism; D020156:Salicylic Acid / Q000378:metabolism*; D015398:Signal Transduction; D014774:Virulence; D016959:Xanthomonas campestris / Q000472:pathogenicity / Q000502:physiology
chemical_list: D010940:Plant Proteins; D017382:Reactive Oxygen Species; D010650:Phenylalanine Ammonia-Lyase; D020156:Salicylic Acid
keywords: Arabidopsis; Xanthomonas campestris pv. Vesicatoria.; defence; pepper; phenylalanine ammonia-lyase