|Rooney, Alejandro - Alex|
Submitted to: Insect Biochemistry and Molecular Biology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/24/2004
Publication Date: 12/1/2004
Citation: Rodriguiz, S., Liu, W., Hao, G., Pina, B., Rooney, A.P., Camps, F., Roelofs, W., Fabrias, G. 2004. Expression and evolution of delta-9 and delta-11 desaturase genes in the moth, Spodoptera littoralis. Insect Biochemistry and Molecular Biology. 34(12):1315-1328. Interpretive Summary: In addition to the obvious economic losses caused by caterpillars as a result of physical damage to crops, these pests also pose food safety risks due to the incidental growth of mycotoxin-producing fungi on parts of the crop plants damaged by caterpillars. The use of synthetic sex pheromones (sex attractants) to control moth pests is an appealing alternative to the use of chemical pesticides. In this study, we describe four new sex pheromone genes from the cotton leafworm moth Spodoptera littoralis as well as the biochemical pathways used to synthesize the pheromones produced by these genes. These new findings provide the necessary information for the development of pheromone-based monitoring and biocontrol strategies for this species.
Technical Abstract: Desaturation of fatty acids is a key reaction in the biosynthesis of moth sex pheromones. The main component of Spodoptera littoralis sex pheromone blend is produced by the action of d11 and d9 desaturases. In this article we report on the cloning of four desaturase-like genes in this species: one from the fat body (Sls-FL1) and three (Sls-FL2, Sls-FL3 and Sls-FL4) from the pheromone gland. Using a computational/phylogenetic method, as well as functional assays, the desaturase gene products have been characterized. The fat body gene expressed a d9 desaturase that produced Z9-16:Acid and Z9-18:Acid in a (1:4.5) ratio, whereas the pheromone gland Sls- FL2 expressed a D9 desaturase that produced Z9 -16:Acid and Z9-18:Acid in a (1.5:1) ratio. The functional assay using the YEpOLEX yeast expression system and the Ole1 yeast mutant demonstrated that both D9 desaturases produced Z9-14:Acid from 14:Acid. In contrast, transformed yeast grown in the presence of a mixture of 14:Acid and E11-14:Acid produced Z9,E11-14:Acid, but not (Z)-9-tetradecenoic acid. Using a pYES2 expression system and a double mutant Ole1/Elo1 yeast strain, Sls-FL3 expressed a protein that produced a mixture of E11-14:Acid, Z11-14:Acid, Z11-16:Acid and Z-11-18:Acid in a 5:4:60:31 ratio. No function could be found for the Sls-FL4 gene. Although it has all the characteristics of a desaturase gene and it is almost identical to the predicted partial sequences of acyl-CoA desaturase of S. litura, S. exigua and Helicoverpa assulta, it does not produce an active enzyme and it might represent either a pseudogene or a gene that is epigenetically repressed or down-regulated.