Expression of a nematode symbiotic bacterium-derived protease inhibitor protein in tobacco enhanced tolerance against Myzus persicae.

Fusion proteins of a protease inhibitor from an entomopathogenic nematode symbiotic bacterium (PIN1) and green fluorescent protein (GFP) were expressed in tobacco (Nicotiana tobacum cv. Samsun NN). The PIN1-GFP protein expressed under the control of the CaMV-35S promoter was detected in leaves of transgenic tobacco plants. The effect of PIN1 on anti-pest activity for Myzus persicae was tested by feeding neonate aphids on three independent homozygous lines. For nymphs fed on PIN1-GFP-expressing plants, no effects on insect survival were observed but average insect weight and fecundity were significantly reduced. The aphid biomass was decreased by 30-35 % compared to those reared on control plants. The effects of PIN1 on M. persicae were correlated with the decrease of the leucine aminopeptidase and total protease activities of whole insect extracts. Furthermore, an increase in polyphenoloxidase activity was observed in PIN1-GFP-expressing plants. These results revealed that the transgenic expression of PIN1 in tobacco enhanced tolerance against aphids. Key message This study suggests that entomopathogenic nematode symbiotic bacterium is another valuable resource of protease inhibitors which can be engineered into plants for insect pest management.