Publication: Plant Sterols and Host Plant Suitability for a Phloem-Feeding Insect
November 19th, 2010
Behmer ST, Grebenok RJ and Douglas AE, 2010. Plant sterols and host plant suitability for a phloem-feeding insect. Functional Ecology. Epub 11/19/2010 DOI: 10.1111/j.1365-2435.2010. 01810.x Journal link
Sterols are essential nutrients for insects which (unlike vertebrates) cannot synthesize these compounds. Angela Douglas is part of a collaborative team with Dr Spencer Behmer (Texas A&M) and Dr Bob Grebenok (Canisius College) working on sterol nutrition of aphids. We have demonstrated that the dominant sterol in the phloem sap of tobacco and Chinese cabbage plants is cholesterol, which is traditionally considered an animal sterol. The most abundant sterol in the gross leaf tissue of these plants is sitosterol and stigmasterol, respectively, with very low levels of cholesterol.
We investigated the effect of sterol structure on the green peach aphid Myzus persicae using modified tobacco plants that contained high levels of atypical steroids, specifically ketone-steroids. Aphids reared on the modified tobacco plants had a high atypical steroid content, severely reduced reproduction and high mortality.
Our data indicate that the total sterol composition of plants is not necessarily representative of the sterol profile available to phloem-feeding insects, and that the sterol utilization patterns of phloem-feeding insects may differ from chewing insect herbivores utilizing the same plant. Atypical steroids are naturally at insufficient concentrations for significant deleterious effects on insect herbivores, and possible reasons why plants apparently do not use them as defensive compounds are considered.
We are carrying this research forward, to develop novel plant resistance strategies against aphids and other phloem-feeding insect pests, based on the sterol content of plant phloem sap.
Figure: The aphid Myzus persicae was administered to control and modified tobacco plants. One week later (shown), the population of aphids had increased rapidly on the control plants, stunting growth. The modified plants were near-aphid free and had grown well over the same period.