The pepper 9-lipoxygenase gene CaLOX1 functions in defense and cell death responses to microbial pathogens.
Lipoxygenases (LOXs) are crucial for lipid peroxidation processes during plant defense responses to pathogen infection. A pepper (Capsicum annuum) 9-LOX gene, CaLOX1, which encodes a 9-specific lipoxygenase, was isolated from pepper leaves. Recombinant CaLOX1 protein expressed in Escherichia coli catalyzed the hydroperoxidation of linoleic acid, with a K(m) value of 113. 9 mum. Expression of CaLOX1 was differentially induced in pepper leaves not only during Xanthomonas campestris pv vesicatoria (Xcv) infection but also after exposure to abiotic elicitors. Transient expression of CaLOX1 in pepper leaves induced the cell death phenotype and defense responses. CaLOX1-silenced pepper plants were more susceptible to Xcv and Colletotrichum coccodes infection, which was accompanied by reduced expression of defense-related genes, lowered lipid peroxidation, as well as decreased reactive oxygen species and lowered salicylic acid accumulation. Infection with Xcv, especially in an incompatible interaction, rapidly stimulated LOX activity in unsilenced, but not CaLOX1-silenced, pepper leaves. Furthermore, overexpression of CaLOX1 in Arabidopsis (Arabidopsis thaliana) conferred enhanced resistance to Pseudomonas syringae pv tomato, Hyaloperonospora arabidopsidis, and Alternaria brassicicola. In contrast, mutation of the Arabidopsis CaLOX1 ortholog AtLOX1 significantly increased susceptibility to these three pathogens. Together, these results suggest that CaLOX1 and AtLOX1 positively regulate defense and cell death responses to microbial pathogens.
Hwang
In Sun
IS
Laboratory of Molecular Plant Pathology, School of Life Sciences and Biotechnology, Korea University, Seoul 136-713, Republic of Korea.
Hwang
Byung Kook
BK
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D002212:Capsicum / Q000201:enzymology / Q000235:genetics* / Q000276:immunology; D020231:Colletotrichum; D018744:DNA, Plant / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D015723:Gene Library; D015227:Lipid Peroxidation; D008084:Lipoxygenase / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D008969:Molecular Sequence Data; D010935:Plant Diseases / Q000235:genetics* / Q000276:immunology; D010940:Plant Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D020156:Salicylic Acid / Q000378:metabolism; D017422:Sequence Analysis, DNA; D016959:Xanthomonas campestris
D018744:DNA, Plant; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D008084:Lipoxygenase; D020156:Salicylic Acid