Cloning And Molecular Evolution Of The Aldehyde Dehydrogenase2Gene (Aldh2)in Bats (Chiroptera)

Old World fruit bats (Pteropodidae) and New World fruit bats (Phyllostomidae) are phytophagous bats which feed mainly on fruit, nectar and pollen. These two kinds of bats are also called frugivorous and nectarivorous bats. Old World fruit bats and New World fruit bats ingest significant quantities of ethanol along with the fruit and nectar while foraging. And whether fruit bats have evolved mechanisms to avoid high ethanol consumption has long been a hot issue. Although several researches focused on physiology and behavior have showed some clues, the evidence of molecular evolution is still rare. Mitochondrial aldehyde dehydrogenase (ALDH2, encoded by the Aldh2gene) plays an important role in ethanol metabolism. The oxidization of acetaldehyde to acetate is a key step in ethanol metabolism, as acetaldehyde is toxic and thought to be involved in many pharmacological and behavioral effects resulting from ethanol intake. To test whether the Aldh2gene has undergone adaptive evolution in frugivorous and nectarivorous bats in relation to ethanol elimination, we sequenced part of the coding region of the gene (1,143bp,～73%coverage) in14bat species, including three Old World fruit bats (Cynopterus sphinx, Rousettus leschenaultii and Eonycteris spelaea) and two New World fruit bats (Artibeus lituratus and Leptonycteris yerbabuenae). Our results showed that the Aldh2coding sequences are highly conserved across all bat species we examined, and no evidence of positive selection was detected in the ancestral branches leading to Old World fruit bats and New World fruit bats. Further studies are needed to determine whether other genes involved in ethanol metabolism have been the targets of positive selection in frugivorous and nectarivorous bats.