Common molecular underpinnings of insect diapause: The role of PEPCK

Hallmark traits of insect diapause include arrested development, depressed metabolism and enhanced stress tolerance. The molecular means through which these phenotypes are achieved in the diapauses of diverse insect species is not necessarily the same, but analyses of several insect diapauses at the molecular level have revealed a few candidate genes that appear to be conserved. These genes are either up- or down-regulated during diapause, although directionality of expression is species dependent for some of these genes. The gene encoding Phosphoenolpyruvate Carboxykinase (PEPCK) is one such gene that appears to be up-regulated in multiple insect diapauses. PEPCK is an enzyme involved in glycero- and gluconeogenesis, or the production of new glycerol and glucose, respectively, and is up-regulated not only during diapause but also in response to stresses such as thermal shock and starvation. Interestingly, there are two isoforms of PEPCK - Mitochondrial (PEPCK-M) and Cytosolic (PEPCK-C). Each isoform is coded for by its own gene, and as the names suggest they will localize to either the mitochondria or cytosol. Currently, it is unknown which isoform of PEPCK is up-regulated during diapause or in response to stress. The purpose of this study is to elucidate the function of these genes in mediating the physiological responses of diapause in the flesh fly, Sarcophaga bullata (Diptera; Sarcophagidae). Future work is designed to manipulate the expression of these genes, thus allowing us to probe their functions during diapause.