Fusion of a soybean cysteine protease inhibitor and a legume lectin enhances anti‐insect activity synergistically

Abstract

1 The soybean cysteine protease inhibitor soyacystatin N (scN) and Griffonia simplicifolia lectin II (rGSII) have defense functions against the coleopteran cowpea bruchid beetle Callosobruchus maculatus. However, the ability of the insect to activate scN-insensitive digestive proteases and the relatively low potency of rGSII have hindered their practical application in plant protection. 2 Recent research suggests that defense proteins may achieve increased toxicity and durability when used in combination. Based on the structures of several natural toxin molecules, we hypothesized that covalently linked scN and rGSII could exhibit greater anti-insect efficacy than the mixture containing individual proteins. 3 To test this hypothesis, a recombinant scN-rGSII fusion protein that retained both protease inhibitor and lectin functions was constructed. 4 When fed to cowpea bruchid, this new protein showed a synergistic delay in insect development, whereas a mixture of the separate proteins only showed an additive effect. 5 Our results suggest that tethering digestive protease inhibitors to gut epithelium-interacting lectins could give plant protection superior to strategies based on single genes or mixtures of single gene products.

A hybrid, broad-spectrum inhibitor of Colorado potato beetle aspartate and cysteine digestive proteinases

“…Whereas the effectiveness of single proteinase inhibitors in plant protection has been questioned in several instances (for a recent discussion, see Brunelle et al, 2004), increasing evidence in the literature suggests the potential of using these resistance factors in combination to allow multiple inhibitions, minimal compensation, and effective protection against herbivorous predators in vivo (Urwin et al, 1998;Inanaga et al, 2001;Outchkourov et al, 2004). Plant protection strategies based on complementary protein fusion partners including proteinase inhibitors (Inagana et al, 2001;Zhu-Salzman et al, 2003b) or other proteins (Fitches et al, 2002(Fitches et al, , 2004) is now seen as a promising approach in plant protection, by which multiple resistance factors with different modes of action are integrated in plant genomes to act together in a coordinated or complementary manner (Ferry et al, 2004). Work is currently underway to assess the potential of CDI-cystatin fusions in plant protection, and the general usefulness of plant CDIs in generating hybrid, chimeric proteins with anti-cathepsin D-like activity.…”

Deterrent activity of plant lectins on cowpea weevil Callosobruchus maculatus (F.) oviposition

“…During the last two decades numerous reports were published on the insecticidal activity of plant lectins against many insect pests belonging to the orders of Lepidoptera, Coleoptera, Diptera and Homoptera (Boulter et al, 1990;Gatehouse et al, 1995;Hilder et al, 1995;Sharma et al, 2004). Interestingly, some of these reports provided evidence for a moderate to strong inhibition for dietary lectins on larval development of C. maculatus (Murdock et al, 1990;Oliveira et al, 1999;Omitogun et al, 1999;Machuka et al, 2000;Zhu-Salzman et al, 2003;Sharma et al, 2004).…”

Multiple insect resistance in transgenic tomato plants over-expressing two families of plant proteinase inhibitors

“…In this respect, expression of the snowdrop lectin gene (gna) from Galanthus nivalis in transgenic rice has been shown to confer substantial protection against sap-sucking insects such as small brown planthopper and green leafhopper (Wu et al, 2002;Nagadhara et al, 2003). Gene pyramiding by expression of proteinase inhibitor fusions to these insecticidal proteins might then be an attractive option for integrated pest management since a recombinant fusion of the soybean cysteine protease inhibitor to the rGSII lectin from Griffonia simplicifolia was recently shown to synergistically enhance anti-insect activity of the soybean cystatin inhibitor by tethering it to the insect gut epithelium, thus increasing the inhibitor midgut perduration (Zhu-Salzman et al, 2003).…”