Cloning and characterization of a Solanum torvum NPR1 gene involved in regulating plant resistance to Verticillium dahliae.

摘要

Non-expressor of pathogenesis-related protein 1 (NPR1) is a transcriptional factor of systemic acquired resistance in plants. In our previous study, a cDNA representing a NPR1 gene (designated NPR1) was screened to be responsive to the infection of Verticillium dahliae ( V. dahliae) by the method of cDNA-amplified restriction fragment polymorphism (cDNA-AFLP), in a wild eggplant species ( Solanum torvum, SW) which is highly resistant to Verticillium wilt. StoNPR1 is 1743 bp and contains an ORF encoding 581 amino acid residues with an estimated molecular mass of 65.46 kDa and a calculated pI of 5.58, and different from AtNPR1 (ABR46023), NgNPR1(ABX71071), and other orthologs, StoNPR1 contain two ankyrin repeat domains. Semi-quantitative RT-PCR assay indicated that the highest expression level of StoNPR1 occurred in the roots but it was less abundant in the leaves and stems. When treated with 300 m salicylic acid and V. dahliae, the transcript expression of StoNPR1 was significantly upregulated. Subcellular localization analysis revealed that the StoNPR1 protein was localized predominantly in the nucleus but it was also present in the cytoplasm. To investigate whether StoNPR1 regulated plant resistance to V. dahliae infection, we expressed StoNPR1 in V. dahliae sensitive potato. Antifungal assay in vitro and plant disease resistance analysis revealed that the over-expression lines were more resistant to V. dahliae, whereas the RNAi lines were susceptible, compared to the wild-type control. The expression of isochorismate synthase 1 and PR1a was significantly upregulated in the StoNPR1 over-expression lines and strongly induced by V. dahliae infection. These results revealed that StoNPR1 gene could regulate the resistance of the transgenic potato lines to V. dahliae infection.