CONSTRUCTION OF AN IMPROVED MYCOINSECTICIDE OVEREXPRESSING A TOXIC PROTEASE

Mycoinsecticides are being used for the control of many insect pests a s an environmentally acceptable alternative to chemical insecticides. A key aim of much recent work has been to increase the speed of kill a nd so improve commercial efficacy of these biocontrol agents, This mig ht be achieved by adding insecticidal genes to the fungus, an approach considered to have enormous potential for the improvement of biologic al pesticides, We report here the development of a genetically improve d entomopathogenic fungus, Additional copies of the gene encoding a re gulated cuticle-degrading protease (Pr1) from Metarhizium anisopliae w ere inserted into the genome of M. anisopliae such that Pr1 was consti tutively overproduced in the hemolymph of Manduca sexta, activating th e prophenoloxidase system, The combined toxic effects of Pr1 and the r eaction products of phenoloxidase caused larvae challenged with the en gineered fungus to exhibit a 25% reduction in time of death and reduce d food consumption by 40% compared to infections by the wild-type fung us, In addition, infected insects were rapidly melanized, and the resu lting cadavers were poor substrates for fungal sporulation. Thus, envi ronmental persistence of the genetically engineered fungus is reduced, thereby providing biological containment.