Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/5/2008
Publication Date: 7/8/2008
Citation: Subramanyam, S., Smith, D., Clemens, J.C., Webb, M.A., Sardesai, N., Williams, C.E., 2008. Functional Characterization of HFR-1, a high-mannose N-glycan-specific wheat lectin induced by Hessian fly larvae. Plant Physiology. 147:1412-1426. Interpretive Summary: Little is known about mechanisms of resistance involved in interactions between wheat and the Hessian fly. We showed that a wheat protein functions to deter Hessian fly larvae from feeding on the plant. In addition, we synthesized the pure protein and fed it to fruit fly larvae, demonstrating that at low concentrations it deterred feeding and at higher doses it killed the larvae. Hessian fly larval behavior on resistant and susceptible plants was scored, showing that larvae on resistant plants never settle into a feeding site and die of starvation. This protein may be useful in transgenic plants as an insect feeding deterrent. And would benefit scientists working on many other types of crops as well as farmers.
Technical Abstract: We previously identified and cloned a novel jacalin-like lectin gene, Hfr-1 (Hessian fly-response gene 1), from wheat (Triticum aestivum L.) plants infested by Hessian fly [Mayetiola destructor (Say)], a major dipteran pest. The resistant plants infested with Hessian fly larvae showed higher levels of Hfr-1 transcripts as compared to uninfested or susceptible plants. Here we report the expression and isolation of soluble, active amounts of recombinant His-tagged full-length HFR-1 in Escherichia coli. Functional characterization of the protein using hemagglutination assays revealed lectin activity. Glycan microarray binding assays showed strong affinity of HFR-1 to man ' 3-6 glycan structures. The feeding site of the avirulent Hessian fly larvae showed the accumulation of high amounts of HFR-1 as revealed by immunodetection using affinity-purified polyclonal antibodies, but HFR-1 was conspicuously absent in the avirulent larvae suggesting a correlation between the induction of HFR-1 and the lack of feeding by the avirulent larvae. Behavioral studies of the avirulent and virulent Hessian fly larvae on the wheat plants showed that the avirulent larvae on the resistant plants exhibit incessant searching and writhing behavior that correlates with HFR-1 protein accumulation in the plant, leading to failure in establishing feeding sites. Diet incorporated feeding bioassays with Drosophila melanogaster larvae revealed significant delays in larval growth and development, and increased mortality of the larvae with progressively increasing doses of HFR-1 indicating the anti-nutritive properties of the protein. Thus, HFR-1 plays a significant role in deterring Hessian fly larvae from feeding on resistant wheat plants.