The phenylalanine pathway is the main route of salicylic acid biosynthesis in Tobacco mosaic virus-infected tobacco leaves
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In plants, salicylic acid (SA), a molecule important for resistance to pathogens, is synthesized from phenylalanine or isochorismate. Although SA is reportedly synthesized via the isochorismate pathway in pathogen-infected <i>Arabidopsis</i>, the predominant pathway in pathogen-infected tobacco has not been known. To determine the pathway in tobacco, we studied the gene expression and enzyme activity of phenylalanine ammonia-lyase (PAL) and isochorismate synthase (ICS) in tobacco leaves infected with <i>Tobacco mosaic virus</i> (TMV). Two days after TMV inoculation, necrotic lesions had appeared, and the levels of SA, PAL activity, and transcripts of <i>PAL A</i> and <i>PAL B</i> had increased substantially. In contrast, no ICS activity was detected, and the levels of <i>ICS</i> transcript did not increase, after the formation of necrotic lesions caused by TMV infection. These results suggest that SA is synthesized mainly by the phenylalanine pathway in TMV-infected and necrotic-lesion-bearing tobacco leaves.
- Plant tissue culture letters
Plant tissue culture letters 23(4), 395-398, 2006-09-01
Japanese Society for Plant Cell and Molecular Biology