| Spodoptera litura is one of the most important agriculture pests of Lepidoptera. It has perfect evolved sex pheromone mating system. The female can release sex pheromone from pheromone gland, then they can rely on it to attract male and cause mating behaviors. The S. litura sex pheromone is the mixture of 14 carbon chains with unsaturated fatty acid esters derivatives. Their synthesis has experienced a serious of processes including palmitic acid biosynthesis, chain shortening reaction, desaturation reaction and functional group modifications. In this pathway, a variety of enzymes participated and catalyzed different of biochemical reaction.In this study, according to the existing transcriptome data and combine sex pheromone biosynthetic pathway of S. litura, we have screened a serious of genes involved in sex pheromone biosynthesis, and aligned them with sex pheromone synthetic genes in other species in NCBI database. Finally we have screened 90 genes and classified into five groups which are Fatty acid synthase, Beta oxidase enzyme system, Fatty acyl-Co A reductase, desaturase and Acetyl-Co A acetyltransferase. In order to investigate their expression levels in both sexes, we used female and male abdomens as the templates, and performed the screen using semi-quantitative PCR method. The results show that the expressions of the majority of genes were not different between female and male, but there are a few of genes which were expressed exclusively in female. Furthermore, we also found that some of them have different expression levels in female and male. So we use QRT-PCR to further testing their expression and calculate multiple relationships between two templates. The results showed that some of genes’ expression levels in females are 3 to 10 times higher than those in males. In addition, we aimed at specific expression of genes in females to study the various expressions in females’ pheromone gland and other tissues in abdomen. The results showed that the expression levels of a majority of genes was conspicuous higher in pheromone gland(p<0.05), while only a few genes held the higher expression level in the other tissues in abdomen. Moreover, nine genes which belonging to different types(fatty acid synthase, desaturase, fatty acyl-Co A reductase) and have different expression characteristics were cloned and their ds RNAs were synthesized. The ds RNA were then injected into female moths to silence genes. According to RT-PCR, we assessed the effective of gene silencing and analyzed the change of components in pheromone on basis of GC-MS. It turned out that after injecting ds RNA, the expression of corresponding genes has decreased, besides, after gene silencing of Des3, Des5 and FAR17, the relative proportions of four sex pheromones which was released by female moth were changed. Finally, we have also explored the expression level of female specificity genes in different geographical flora. The results showed that some genes had the tremendous express differences in different areas, but some of them had the same expression level in different areas.Studying the function and expression characteristic in different regions of genes involved in Spodoptera litura sex pheromone synthesis could help us to understand the intra-specific sex pheromone variation and speculate its direction of evolution, furthermore, this study can provide theoretical basis for disturbing moths mating by biosynthesis sex pheromone and provide important support for pest control in the field using sex pheromone. |
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