Gene Expression and Metabolic Analyses of Nontransgenic and AtPAP1 Transgenic Tobacco Infected with Potato Virus X (PVX)

Potato virus X (PVX), a species of the genus Potexvirus, is a plant pathogenic virus that causes severe symptoms such as mild mosaic, crinkling, necrosis, and mottling on leaves. The objectives of the present study were to investigate the effect of PVX virus infection on the metabolic system in nontransgenic and Arabidopsis thaliana production of anthocyanin pigment 1 (AtPAP1) transgenic tobacco using transcript expression analysis and metabolic profiling. Potato virus X inoculation increased the gene expression of phenylpropanoid and flavonoid biosynthesis and the production of chlorogenic acid, p-coumaric acid, benzoic acid, rutin, quercetin, and kaempferol in nontransgenic tobacco leaves. However, in the AtPAP1 transgenic tobacco leaves, PVX inoculation decreased the expression of AtPAP1 and phenylpropanoid and flavonoid biosynthesis genes, and the production of phenolics and anthocyanin also declined. In contrast, the levels of amino acids and tricarboxylic acid (TCA) cycle intermediates increased after infection in the AtPAP1 transgenic plant leaves. To date, these results have not been reported previously. We suggest that PVX infection decreases AtPAP1 expression, leading to the downregulation of phenylpropanoid and flavonoid biosynthesis in transgenic plants.