A Vip3Af mutant confers high resistance to broad lepidopteran insect pests

Vegetative insecticidal proteins (Vip3) from Bacillus thuringiensis (Bt) have been utilized for control of lepidopteran insect pests. The majority of known Vip3 proteins possess exceptional high toxicity against Noctuid insects such as the fall armyworm (FAW, Spodoptera frugiperda), beet armyworm (BAW, Spodoptera exigua) and cotton bollworm (CBW, Helicoverpa armigera), but generally have relatively low or even no activity against some very important pest insects, such as Asian corn borer (ACB, Ostrinia furnacalis), European corn borer (ECB, Ostrinia nubilalis), rice stem borer (RSB, Chilo suppressalis) and oriental armyworm (OAW, Mythimna separata).

Here, we report mutant Vip3Af with a single amino acid mutation, Vip3Af-T686R, which gains significantly higher insecticidal activity against ACB, OAW and BAW, while retaining high activity against FAW, CBW and RSB. Protein proteolytic activation in vitro showed that the proteolytic activation efficiency of the mutant protein was greater than the wild-type protein in the midgut juice of ACB, OAW and BAW. Transgenic corn expressing this mutant Vip3Af showed high levels of resistance to ACB, OAW, FAW, BAW and CBW.

Our results suggest that Vip3Af may be a superior Vip3A mutant for the development of transgenic crops with resistance to a broad range of lepidopteran pest species. © 2024 Society of Chemical Industry.