Abstract
The homopteran sucking insect, Lipaphis erysimi (mustard aphid) causes severe damage to various crops. This pest not only affects plants by sucking on the phloem, but it also transmits single-stranded RNA luteoviruses while feeding, which cause disease and damage in the crop. The mannose-binding Allium sativum (garlic) leaf lectin has been found to be a potent control agent of L. erysimi. The lectin receptor protein isolated from brush border membrane vesicle of insect gut was purified to determine the mechanism of lectin binding to the gut. Purified receptor was identified as an endosymbiotic chaperonin, symbionin, using liquid chromatography-tandem mass spectrometry. Symbionin from endosymbionts of other aphid species have been reported to play a significant role in virus transmission by binding to the read-through domain of the viral coat protein. To understand the molecular interactions of the said lectin and this unique symbionin molecule, the model structures of both molecules were generated using the Modeller program. The interaction was confirmed through docking of the two molecules forming a complex. A surface accessibility test of these molecules demonstrated a significant reduction in the accessibility of the complex molecule compared with that of the free symbionin molecule. This reduction in surface accessibility may have an effect on other molecular interactive processes, including "symbionin virion recognition", which is essential for such symbionin-mediated virus transmission. Thus, garlic leaf lectin provides an important component of a crop management program by controlling, on one hand, aphid attack and on the other hand, symbionin-mediated luteovirus transmission.
Highlights
The homopteran pest Lipaphis erysimi, commonly known as the mustard aphid, causes major damage to oil seed crops
We demonstrated previously [16, 17] the detrimental effects of the mannose-binding Allium sativum leaf (ASAL) and bulb (ASA) lectins on the growth and development of L. erysimi when provided in an artificial diet bioassay
Such SymL protein has been reported previously to be coded by a mutualistic intracellular symbiotic bacteria, Buchnera aphidicola. It resides in a specialized tissue of the insect gut, which supplies several essential amino acids to aphids that they do not get from plant sap [18]. This SymL binds to the read-through domain (RTD) of the coat protein of the single-stranded virus particles located in the hemocoel and escorts them to the salivary gland and helps the viruses to be transmitted to different plants while the aphids feed on them [1,2,3,4]
Summary
Mustard aphids (L. erysimi) were obtained from our institutional experimental farm and maintained on live mustard plants or artificial diets. Competitive Inhibition of ASAL-receptor Interaction in Presence of Mannose and Ligand Blot Analysis after Deglycosylation of the Receptor—Total aphid BBMV proteins, dissolved in 1% sodium deoxycholate and dialyzed, were run on two separate 12% SDS-polyacrylamide gels, and both of these were transferred onto Hybond-C membranes and marked as “A” and “B.” The ligand blot analysis mentioned above was performed on two membranes, one modification was introduced for membrane B wherein 1 nM ASAL pre-incubated with 1 M ␣-D-mannose was used instead of “only ASAL.” After this point, the ligand blot analysis was carried out on both the membranes as mentioned earlier [16]. This oligosaccharide moiety was covalently added to the Asn133 position of the modeled SymL using
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