Baculovirus expression of the maize mitochondrial protein URF13 confers insecticidal activity in cell cultures and larvae.
The URF13 protein, which is encoded by the mitochondrial gene T-urf13, is responsible for cytoplasmic male sterility and pathotoxin sensitivity in the Texas male-sterile cytoplasm (cms-T) of maize. Mitochondrial sensitivity to two host-specific fungal toxins (T toxins) is mediated by the interaction of URF13 and T toxins to form pores in the inner mitochondrial membrane. A carbamate insecticide, methomyl, mimics the effects of T toxins on isolated cms-T mitochondria. URF13 was expressed in Spodoptera frugiperda (fall army-worm) cells (Sf9) in culture and in Trichoplusia ni (cabbage looper) larvae with a baculovirus vector. In insect cells, URF13 forms oligomeric structures in the membrane and confers T toxin or methomyl sensitivity. Adding T toxin or methomyl to Sf9 cells producing URF13 causes permeabilization of plasma membranes. In addition, URF13 is toxic to insect cells grown in culture without T toxins or methomyl; even a T-toxin-insensitive mutant form of URF13 is lethal to cell cultures. Baculoviruses expressing URF13 are lethal to T. ni larvae, at times postinjection comparable to those obtained by injecting a baculovirus expressing an insect neurotoxin. This result suggests that URF13 could be useful as a biological control agent for insect pests. Our data indicate that URF13 has two independent mechanisms for toxicity, one that is mediated by T toxin and methomyl and one that is independent of these toxins. Similarly, male sterility and toxin sensitivity in cms-T maize may be due to independent mechanisms.
Korth
K L
KL
Department of Genetics, North Carolina State University, Raleigh 27695-7614.
Levings
C S
CS
D000818:Animals; D016367:Baculoviridae / Q000235:genetics*; D001483:Base Sequence; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004247:DNA / Q000235:genetics; D007814:Larva; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D009036:Moths / Q000187:drug effects*; D009838:Oligodeoxyribonucleotides; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism* / Q000633:toxicity*; D003313:Zea mays / Q000235:genetics / Q000502:physiology*
D024101:Mitochondrial Proteins; D009838:Oligodeoxyribonucleotides; D010940:Plant Proteins; C071393:URF13 protein, Zea mays; D004247:DNA