We identified and engineered a number of beneficial genes for targeting the sugar beet root maggot (Tetanops myopaeformis Roder), a major insect pest of sugar beet in the United States and Canada. One class of genes targets the insect’s digestive system to prevent the assimilation of nutrients from ingested foods thus inhibiting normal growth and development. We demonstrated three predominant classes of protease activity in the midguts of feeding second instar maggots. Pepstatin A and squash aspartyl proteinase inhibitor, with activity toward aspartyl proteases, were effective inhibitors at an acidic pH (greater than 90% inhibition). PMSF and soybean trypsin-chymotrypsin inhibitor, that target serine proteases, reduced proteolysis by 50 and 90%, respectively. E-64 and oryzacystatin I, with high potency toward cysteine proteinases, had a minor inhibitory activity (7 and 20%, respectively). We also demonstrated that cytokinin-induced insecticidal compounds killed more than 90% of the maggot larvae suggesting that manipulation of the plant biosynthetic pathways for the production of these toxic compounds may be an effective control strategy for the maggot. Studies were also initiated to profile the defense response genes in maggot resistant sugar beet lines. We developed an in vitro root maggot bioassay using resistant and susceptible parental lines to generate infested tissues for preparation of cDNA libraries enriched for resistance genes. Clones with potential roles in root maggot (and disease) resistance are being molecularly and biochemically characterized. Defense gene profiling will provide useful information for developing new control strategies for the root maggot and other pests.
Species 1: Diptera Otitidae Tetanops myopaeformis (Sugarbeet root maggot)
Keywords: transgenic crops, proteinase inhibitor
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