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United States Department of Agriculture

Agricultural Research Service

Title: Nematode Steroids: Recent Discoveries About Metabolism and Function

Authors
item Chitwood, David
item Skantar, Andrea

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 13, 2006
Publication Date: June 5, 2006
Citation: Chitwood, D.J., Skantar, A.M. 2006. Nematode steroids: recent discoveries about metabolism and function [abstract]. XXVIII Symposium of the European Society of Nematologists. p. 42.

Technical Abstract: Because nematodes nutritionally depend upon their hosts for sterols, steroid metabolism is an attractive area of investigation for development of new methods of nematode management. In experiments involving Caenorhabditis elegans as a model for phytoparasitic nematodes, C. elegans removed the methyl or ethyl substituents present at the C-24 position of the sterol side chain; C-24 alkyl groups are typical of plant sterols but are usually absent in animals. This dealkylation process was inhibited by 25-azacoprostane. Proteomic analysis of 25-azacoprostane-treated C. elegans revealed inhibitor-induced reductions in the levels of several proteins. Additionally, C. elegans can perform several metabolic transformations upon the sterol nucleus, such as double bond introduction, removal, or isomerization. The ability of C. elegans and other nematodes to introduce a methyl group at C-4 of the sterol nucleus is unique to nematodes; nematode development can be disrupted by an inhibitor of an isomerase in the 4-methylation pathway. Collaborative investigations studies have indicated that 4-methylsterols play a specific role in nematodes, and that transgenic C. elegans with higher than normal levels of cholesterol are more resistant than controls to UV and temperature stresses. We also recently identified two genes in Heterodera glycines similar to 17-beta-hydroxysteroid dehydrogenases involved in the synthesis of steroid hormones in mammals. Quantitative real-time PCR revealed the highest expression of both genes in developing females, with relatively low levels in second-stage juveniles, eggs, or males. These 17-beta-hydroxysteroid dehydrogenases may be involved in the conversion of sterols into nematode steroid hormones.

Last Modified: 8/30/2014
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