Characterization of NIPRa, a pathogenesis-related protein from Solanum lycopersicum
Date Issued
2012
Date
2012
Author(s)
Yi, Siao-Huei
Abstract
Phosphonate-based fungicides such as neutralized phosphorous acid (NPA) are known to induce plant resistance against many diseases, including those caused by Phytophthora. To investigate the mechanism underlying NPA-induced resistance, we previously performed a microarray analysis and found that a variety of defense genes were induced in response to NPA treatment on tomato plants. Among them, one gene (named NPA-induced pathogenesis-related protein a, NIPRa), which showed homology to a putative pathogenesis-related (PR) gene in barley, is significantly induced but functionally unknown. Hence, the aim of this study is to uncover the characteristics of NIPRa. Analysis by semi-quantitative reverse transcriptase-PCR indicated that expression of NIPRa was induced when plants were challenged with either P. parasitica or the bacteria wilt pathogen Ralstonia solanacearum. NIPRa was up-regulated by salicylic acid and ethylene treatment as well. To test whether NIPRa contributes to plant resistance against pathogens, we overexpressed NIPRa by PVX agroinfection, and then challenged the plants with either P. parasitica or R. solanacearum. Plants overexpressing NIPRa showed higher tolerance to infection by these pathogens. In contrast, down-regulation of NIPRa by TRV-induced gene silencing increased plant susceptibility to pathogen infection. In addition, the promoter of NIPRa gene was analyzed by agroinfiltration of tobacco leaves, using GUS as a reporter, to define sequence elements that are required for P. parasiticaresponse. The result showed that a 351-bp region between 248 and 599 bp upstream of NIPRa translation start site was essential for induction by P. parasitica. Furthermore, the NIPRa recombinant protein purified from E. coli showed green color and tended to form dimers to polymers when analyzed by gel filtration. Analysis by ICP-MS indicated that it is most likely a metalloprotein associated with nickel ion. These results suggested that NIPRa may represent a novel category of PR protein, yet its function needs further investigation.
Subjects
neutralized phosphorous acid (NPA)
pathogenesis-related (PR) gene
promoter analysis
Phytophthora parasitica
Ralstonia solanacearum
Type
thesis
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