부산대학교 도서관

Chemically induced host resistance is useful phenomenon for comprehending host innate immunity against plant pathogens. To evaluate immune priming against cucumber mosaic virus (CMV) infection, we sprayed benzothiadiazole (BTH), a salicylic acid (SA) analog, on either one-leaf or entire plants of Nicotiana benthamiana (Nb). The chemical immune priming downregulated transcript level of Salicylic acid glucosyltransferase (SAGT) and upregulated that of Pathogenesis-related protein 1a (PR1a) in the treated and untreated upper leaves of the one-leaf-treated Nb. Fluorescent-protein-expressing CMV vectors revealed inhibitory effect on initial infection and delayed systemic infection in the one-leaf-treated Nb inoculated with the virus vectors, and the BTH was more effective than SA. However, the BTH-induced host defensive response was attenuated when wild-type Nb was infected with the virus before BTH spray of one leaf and by constitutive expression of the 2b protein of CMV (2b) in a transgenic Nb line after BTH spray of one leaf. SAGT was downregulated and PR1a upregulated in the upper, middle, and lower leaves when the entire plant was treated with BTH. Viral levels were reduced in BTH-treated middle and -untreated upper leaves, but not in the emerging and uppermost leaves after the whole plant spray. Taken together, these results suggest that the chemical immune priming is more effective than SA to retard systemic infection of CMV. However, the BTH-mediated antiviral responses can be attenuated by prior CMV infection and by constitutive expression of 2b in Nb, and does not efficiently suppress CMV infection in later-emerging leaves. [ABSTRACT FROM AUTHOR]