Ribosome-inactivating proteins from apple have strong aphicidal activity in artificial diet and in planta

Abstract The apple ( Malus domestica ) genome contains gene sequences encoding type-1 and type-2 ribosome-inactivating proteins (RIPs). Both types of proteins contain a RIP domain with N-glycosidase activity, but the type-2 RIPs possess an additional domain with lectin activity. Here we investigated the activity of RIPs from apple against two sucking-piercing aphids that are important in agriculture, in particular pea aphids ( Acyrthosiphon pisum ) and green peach aphids ( Myzus persicae ). When the recombinant RIPs were dosed in an artificial liquid diet against pea aphids a strong aphicidal activity was observed. Based on LC 50 s, the type-2 RIP (33 mg/L) was about 10 times more active than the type-1 RIP (341 mg/L), and the LC 50 of the recombinant protein corresponding to the type-2 RIP lectin domain alone was 106 mg/L. In in planta experiments with transgenic tobacco plants expressing the type-1 RIP or the type-2 RIP and infected with green peach aphids, mortalities of the nymphal stages amounted to approximately 50% for both types of transgenic lines when compared to wild type plants. In addition, significant sublethal effects were observed in the surviving aphids with a reduction in fecundity, intrinsic rate of increase, net reproductive rate and doubling time of the insect population. The insecticidal activity of the type-1 RIP and type-2 RIP from apple is discussed in relation to the domain structure of the RIPs and potential use in plant protection.