Abstract
We have shown that a small G-protein, NtRac3, overexpressed tobacco (OE-Rac3) showed hypersensitivity to salicylic acid (SA), and rapid induction of SA accumulation and PR-1 gene expression, when the plant was inoculated with a pathogenic, Pseudomonas syringae tabaci (Pst). To further study, defense responses of a tobacco plant that expresses dominant negative form of NtRac3 (DN-Rac3) was investigated. In DN-Rac3, when the plant was inoculated with Pst, expression of PR-1 gene was delayed and the pathogen rapidly grew in leaf tissues. Moreover, when OE-Rac3 was inoculated with a nonpathogen, P. s. glycinea, SA accumulation and PR-1 gene expression at non-inoculated leaves occurred within 24h after inoculation. These results indicate that NtRac3 regulate SAR through control of SA pathway.
