Microarray and Functional Pathway Analyses Revealed Significantly Elevated Gene Expressions Associated with Metabolic...

The tarnished plant bug (TPB, Lygus lineolaris) remains a major pest for a variety of crops. Frequent sprays on row crops, especially cotton, prompted resistance development in field populations. To maintain chemical control as an effective tool against the pest, knowledge of global gene regulations is desirable for better understanding and managing the resistance. Novel microarray expressions of 6688 genes showed 685 significantly upregulated and 1382 significantly downregulated genes in oxamyl-selected TPBs (Vyd1515FF[R]) from a cotton field. Among the 685 upregulated genes (participated in 470 pathways), 176 genes code 30 different enzymes, and 7 of the 30 participate in 24 metabolic pathways. Six important detoxification pathways were controlled by 20 genes, coding 11 esterases, two P450s, two oxidases, and three pathway-associated enzymes (synthases, reductase, and dehydrogenase). Functional analyses showed substantially enhanced biological processes and molecular functions, with hydrolase activity as the most upregulated molecular function (controlled by 166 genes). Eleven esterases belong to the acting on ester bond subclass of the 166 hydrolases. Surprisingly, only one GST showed significant upregulation, but it was not involved in any detoxification pathway. Therefore, this research reports a set of 20 genes coding 6 enzyme classes to detoxify a carbamate insecticide oxamyl in Vyd1515FF. Together with three previous reports, we have obtained the best knowledge of resistance mechanisms to all four conventional insecticide classes in the economically important crop pest. This valuable finding will greatly facilitate the development of molecular tools to monitor and manage the resistance and to minimize risk to environment.