|Chang, Chiou ling|
Submitted to: Journal of Insect Physiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/17/2009
Publication Date: 4/15/2010
Citation: Chang, C.L., Coudron, T.A., Goodman, C., Stanley, D., An, S., Song, Q. 2010. Dietary wheat germ oil influences gene expression in adult oriental fruit fly. Journal of Insect Physiology 56 (2010) 356-365 Interpretive Summary: The oriental fruit fly, Bactrocera dorsalis (Hendel; Tephritidae) extensively damages a broad host range of cultivated fruits and is widely spread in tropical Asia, Hawaii, Guam, the Mariana Islands and Tahiti. Yield losses and fruit quality degradation negatively impact fruit commercialization in these areas and led to implementation of area-wide integrated management programs, including a sterile insect technique (SIT) component. SIT requires continuous mass-rearing, sterilization and release of adult fruit flies. A major improvement in the cost-effective rearing of the oriental fruit fly included the replacement of mill feed bulking agent with a sponge cloth that enable rearing on a liquid diet (Chang et al., 2006). The addition of wheat germ oil (WGO) to the liquid diet improved rearing efficiency by significantly increasing larval development, pupal recovery, percentage of adult fliers, mating, egg production and hatch (Chang and Vargas, 2007; Chang, 2009). The fatty acid composition of WGO includes 42-59% linoleic acid (18:2n-6), 12-18% oleic acid, 11-19% palmitic acid, 2-11% a-linolenic acid (18:3n-3), and stearic acid 1%, and 0.14% of vitamin E. Proportions vary somewhat due to the plant-based source of the product (Kahlon 1989). The influence of WGO in insect nutritional studies was first reported by Fraenkel and Blewett (1946). The improving effects of WGO on insect performance derive from its high content of nutritionally essential and nonessential fatty acids, and from physiologically active tocopherols. Subsequent experiments with pure fatty acids demonstrated that polyunsaturated fatty acids (PUFAs), including oleic acid, linoleic acid (18:2n-6), oleic acid (18:3n-6), and linolenic acid (18:3n-3) are essential nutrients for many insect species (Dadd, 1985). Mosquitoes are peculiar because they specifically require 20:4n-6, which can be derived from dietary 18:2n-6 in most insects. A few insect species are unique among animals because they are able to synthesisze 18:2n-6 de novo (de Renobales et al., 1987). Based on the improved adult performance resulting from the addition of WGO to the liquid diet and recent advances in human nutritional research (de Roos and McArdle, 2008), we generated the hypothesis that one mode of WGO action in insect development is through its influence on gene expression. Reported here the presence of WGO in the diet substantially altered expression of genes encoding a range of proteins in the corresponding adults.
Technical Abstract: Culture media supplemented with wheat germ oil (WGO) exerts observable physiological reactions, such as increased fecundity and mobility, in some insects. Although the impact of WGO on insect physiology is important, the mechanisms of these actions are poorly understood. The hypothesis that the addition of WGO into medium developed for larval oriental fruit flies modulates gene expression in the corresponding adults was tested. Separately reared immature Bactrocera dorsalis on diets lacking, and supplemented with, WGO were analyzed for expressed proteins in the resulting adult males and females by 2-D electrophoresis. Analysis of the gels revealed significant changes in expression levels of >70 proteins, 64 of which were identified by mass spectrometric analysis on MALDI TOF/TOF. The apparent changes in expression levels of 6 proteins were confirmed by quantitative real time PCR or qPCR, showing that the changes in mRNA expression were reflected in changes in protein expression. These finding support the hypothesis that one mechanism of WGO actions in insect nutrition is the modulation of gene expression.