Abstract
Mature N. benthamiana shows strong resistance to potato blight pathogen Phytophthora infestans. Previously, we reported that ethylene signaling mediated by EIN2 is regulating the expression of genes for phytoalexin biosynthesis, NbEAS and NbEAH, which is essential for resistance of N. benthamiana to P. infestans. By screening using virus-induced gene silencing (VIGS), we isolated genes for a PDR-type ABC transporter, NbPDR1, as a required gene for disease resistance. Given PDR1 from N. plumbaginifolia is previously reported as an exporter of a terpenoid sclareol, the role of NbPDR1 was expected to be a transporter of terpenoid phytoalexin capsidiol to the site of pathogen infection. However, NbPDR1-silenced plant showed significantly reduced accumulation of capsidiol induced by treatment of INF1, an elicitor protein derived from P. infestans. In contrast, INF1-induced production of reactive oxygen species was not affected by the silencing of NbPDR1. These results support the conclusion that PDR1 is involved in phytoalexin production in defense of N. benthamiana to P. infestans, possibly intracellular transport of capsidiol precursor in the process of phytoalexin production.
