Sucrose‐dependent increase in oligosaccharide production and associated glycosidase activities in the potato aphid Macrosiphum euphorbiae (Thomas)

Abstract

Osmotic stress due to high sucrose concentration was imposed on the potato aphid, Macrosiphum euphorbiae (Thomas), in an artificial diet situation. Thin layer chromatography resolved melezitose and six additional honeydew oligosaccharides. Significantly higher levels of these oligosaccharides were recovered from the honeydew of this species in response to feeding on increased dietary sucrose concentrations, pointing to an osmoregulatory response. In addition, carbohydrase activities from the potato aphid were described. A degree of specificity toward hydrolysis of the sucrose substrate over other a-glucosyl sugars was demonstrated. Also, sucrose was optimal for the formation of the oligosaccharides. A strong a-galactosidase activity was found and transgalactosylation ability was indicated. These major trends in carbohydrase activity were also found in the foxglove aphid, Acyrthosiphon solani (Kaltenbach), and the oleander aphid, Aphis nerii Fonscolornbe.

Sweet problems: insect traits defining the limits to dietary sugar utilisation by the pea aphid,Acyrthosiphon pisum

“…Phloem-feeding insects assimilate only a proportion of the ingested sugar, after hydrolysis by the gut sucrase to its constituent monosaccharides (Rhodes et al, 1996;Ashford et al, 2000). In aphids, the osmotic pressure of the remaining sugar (which is voided in honeydew) is reduced by a gut transglucosidase, which catalyses the polymerisation of the monosaccharide, especially glucose, into oligosaccharides in the gut Walters and Mullin, 1988;Rhodes et al, 1997;Wilkinson et al, 1997;Ashford et al, 2000). In this way, aphids avoid losing water from their body fluids, especially their haemolymph, to the gut.…”

Effect of the ?-glucosidase inhibitor, bromoconduritol, on carbohydrate metabolism in the silverleaf whitefly,Bemisia argentifolii

“…Depending on the plant species, the soluble carbohydrate in phloem sap can be almost exclusively in the form of the disaccharide sucrose (Zeigler, 1975). Interestingly, most of the excess sucrose ingested by whiteflies and aphids on a high sucrose diet is converted to other sugars before it is excreted (Fisher et al, 1984;Walters and Mullin, 1988;Byrne and Miller, 1991;Hendrix et al, 1992;Rhodes et al, 1997;Wilkinson et al, 1997).…”

Solenopsis invicta(Hymenoptera: Formicidae), DefendPhenacoccus solenopsis(Hemiptera: Pseudococcidae) Against its Natural Enemies

“…Sugar composition may be substantially different among different hemipteran species (Fischer & Shingleton 2001). The ability to transform the ingested disaccharide sucrose also differs significantly among hemipterans species (Fisher et al 1984;Walters & Mullin 1988). For instance, A. fabae and Macrosiphoniella tanacetaria (Kaltenbach) (Hemiptera: Aphididae) are not able to synthesize oligosaccharides, which may play an important role in aphid osmoregulation (Fisher et al 1984;Walters & Mullin 1988;Wilkinson et al 1997).…”

“…The ability to transform the ingested disaccharide sucrose also differs significantly among hemipterans species (Fisher et al 1984;Walters & Mullin 1988). For instance, A. fabae and Macrosiphoniella tanacetaria (Kaltenbach) (Hemiptera: Aphididae) are not able to synthesize oligosaccharides, which may play an important role in aphid osmoregulation (Fisher et al 1984;Walters & Mullin 1988;Wilkinson et al 1997). Symbiotic bacteria in hemipterans may also be responsible for the observed differences in the honeydew composition (Baumann et al 1995;Teo & Woodring 1985).…”