Over-expression of the triploid white poplar PtDrl01 gene in tobacco enhances resistance to tobacco mosaic virus.

A full-length cDNA, designated as the Populus tomentosa disease resistance-like 01 (PtDrl01) gene, was isolated from triploid white poplar [(Populus tomentosa × P. bolleana) × P. tomentosa]. The protein thought to be produced by the PtDrl01 gene contains a nuclear localisation sequence (NLS), a toll/interleukin-1 receptor (TIR) homologue region, a nucleotide binding site (NBS) and a leucine-rich repeat (LRR) domain. The protein also exhibits a considerable degree of homology to N-like resistance proteins. Real-time quantitative RT-PCR analysis revealed that expression of the PtDrl01 gene in triploid white poplar leaves could be induced by two defence signalling molecules: methyl jasmonate (MeJA) and salicylic acid (SA). Over-expression of the PtDrl01 gene in transgenic tobacco induced enhanced resistance to tobacco mosaic virus (TMV). Long-term resistance from the PtDrl01 gene to TMV infection was also observed in transgenic tobacco plants. Additionally, over-expression of the PtDrl01 gene resulted in transcriptional changes in genes expressing pathogenesis-related proteins in transgenic tobacco under non-stress conditions. These data strongly suggest that the PtDrl01 gene is involved in plant defence responses to pathogen infection.