Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 18, 2000
Publication Date: N/A
Interpretive Summary: Silverleaf whiteflies cause serious problems with many subtropical crops through their honeydew secretion and ability to spread plant visuses. They have proven difficult to control by usual chemical means. In searching for unique aspects of their metabolism to utilize as focal points in highly specific control measures, we have been characterizing the carbohydrate metabolism of these insects in some detail. In these analyses, we noted that these insects contained high concentrations of an unusual unknown sugar which didn't match any of our known standards. The present work showed it to be a novel trisaccharide consisting entirely of glucose. In fact, although this sugar had been synthesized chemically, this is the first report of this sugar in a living organism. Results of radioactive labeling experiments suggested that this sugar may be a glucose reserve. Work is currently underway to understand how this sugar is formed and whether or not it is actually utilized by this insect as an energy reserve
Technical Abstract: An unknown sugar was isolated from the silverleaf whitefly, Bemisia argentifolii. Analysis of the chemical and enzymatic digestion products of this unknown sugar showed that it likely consisted entirely of glucose and contained both trehalose and isomaltose moieties. Matrix assisted laser desorption mass spectroscopy confirmed it was a trisaccharide. Tandem mass sspectrometry and nuclear magnetic resonance spectroscopy confirmed that this unknown sugar was a trisaccharide and showed it was O-alpha-D- glucopyranosyl-(1,6)-O-alpha-D-glucopyranosyl-(1,1)-alpha-D- glucopyranoside. A common name of isobemisiose was proposed for this sugar. While this trisaccharide has been previously artificially synthesized, this is the first report of this sugar in a living organism. We found this sugar in two other species of whiteflies at lower levels than in B. argentifolii and at very low levels in five species of aphids. Attempts to determine the enzyme(s) responsible for its synthesis were not successful, but it was shown that enzymes in this insect are capable of digesting this sugar completely to glucose, suggesting that it may serve as a glucose reserve.