Fourth International Bemisia Workshop International Whitefly Genomics Workshop
The involvement of glutathione s-tranferases from Bemisia tabaci (Hemiptera: Aleyrodidae) in plant-insect interactions
Department of Entomology, the Hebrew University of Jerusalem, Faculty of Agricultural, Food and Environmental Quality Sciences, Rehovot, Israel. Correspondence: morin@agri.huji.ac.il
Polyophagous insects like Bemisia tabaci are capable of feeding on a wide range of plant families. As a result, they have to cope with a tremendous diversity of plant defense secondary compounds. In many cases, resistance to these compounds is achieved by the activity of metabolic enzyme families like glutathione s-tranferases (GSTs), which are capable of detoxifying (among other substrates) glucosinolates (GLS), produced mainly by plant species belonging to Brassicaceae. Here, we compared the expression level of three GST genes previously isolated from B. tabaci. Throughout our experiments, B. tabaci individuals were subjected to two Brassicaceae hosts (mustard and cabbage) and one non-Brassicaceae host (cotton). When B. tabaci adults were transferred from cotton to mustard or cabbage, the expression level of all three GST genes increased (1.7–2.74 fold). When adults were returned back to cotton, all three genes showed reduced expression level but only one gene (designated GST2) showed a significant decrease (1.84 fold in transition from mustard to cotton). In order to examine the possibility the B. tabaci individuals are capable of switching on and off their GST genes is response to their plant host, the expression level of the three genes was examined for nine generations. In each generation, adults were allowed to choose between three host plants: cotton, mustard or cabbage and RNA was extracted from each sample. For producing the next generation, we continued only with offspring that chose the same plant species as their female parent (developed on cotton and chose cotton or developed on mustard and chose mustard). Significant increase and decrease in gene expression after switching and switching back between Brassicaceae and cotton was observed only for GST2. AFLP analysis revealed that the mustard and cotton lineages were genetically similar (only 2.8% variation among populations from the two plant species), suggesting that no selection occurred in nine generations. When B. tabaci adults were fed on artificial diet that contained different glucosinolates degradation products, the highest elevation in GST2 expression was observed when nitriles were added. All together, these findings suggest that GST2 is involved in the response of B. tabaci to plants from Brassicaceae and that the insect has the ability to increase the expression level of this gene only when required.