Novel insecticidal proteins from ferns resemble insecticidal proteins from <i>Bacillus thuringiensis</i>

Abstract

Lepidopterans affect crop production worldwide. The use of transgenes encoding insecticidal proteins from <i>Bacillus thuringiensis</i> (<i>Bt</i>) in crop plants is a well-established technology that enhances protection against lepidopteran larvae. Concern about widespread field-evolved resistance to <i>Bt</i> proteins has highlighted an urgent need for new insecticidal proteins with different modes or sites of action. We discovered a new family of insecticidal proteins from ferns. The prototype protein from <i>Pteris</i> species (Order Polypodiales) and variants from two other orders of ferns, Schizaeales and Ophioglossales, were effective against important lepidopteran pests of maize and soybean in diet-based assays. Transgenic maize and soybean plants producing these proteins were more resistant to insect damage than controls. We report here the crystal structure of a variant of the prototype protein to 1.98 Å resolution. Remarkably, despite being derived from plants, the structure resembles the 3-domain Cry proteins from <i>Bt</i> but has only two out of three of their characteristic domains, lacking the C-terminal domain which is typically required for their activities. Two of the fern proteins were effective against strains of fall armyworm that were resistant to <i>Bt</i> 3-domain Cry proteins Cry1Fa or Cry2A.127. This therefore represents a novel family of insecticidal proteins that have the potential to provide future tools for pest control.