Defensin (TvD1) from Tephrosia villosa exhibited strong anti-insect and anti-fungal activities in transgenic tobacco plants

Plant defensin is a small, cationic, cysteine-rich broad-spectrum antimicrobial peptide with four or five disulfide bridges and has been shown to be a component of the innate immunity system in plants. In the present study, the defensin gene (TvD1) from Tephrosia villosa was overexpressed in tobacco and characterized. Two high-expression (T1, T26) and one low-expression (T13) plant lines were selected through semi-quantitative RT-PCR and used for bioassays along with non-transgenic controls. The high-expression plant line exhibited strong in vivo anti-fungal and anti-feedant activity against the pathogen Rhizoctonia solani and the first and second instar larvae of the Spodoptera litura (F.), the tobacco cutworm, respectively. The low-expression plant line showed a moderate level of tolerance/resistance in the bioassays. The recombinant peptide (rTvD1) exhibited toxicity to tobacco pollen grains in the germination assay, but transgenic plants produced copious fertile pollen and set capsules with viable seeds. The results of this study demonstrate that the single gene (TvD1) effectively controls both fungal and insect pests and, hence, it can be used for crop transformation.