Adaptive Evolution Of Myo6Gene In Old World Fruit Bats

Old World fruit bats (Pteropodidae) feed mainly on fruit, flowers, nectar and pollen, the diets which are thought to be poor in protein and especially poor in essential nutrients like fat-soluble vitamins. And how Old World fruit bats subsist on such diets has long been a striking issue. Although several studies focused on behavior and physiology have revealed some clues, molecular evolutionary evidence is still rare. Myosin VI (encoded by Myo6), which the only myosin known to move towards the minus end of the actin filament thus far, is highly expressed in renal proximal tubule cells. The study of myosin VI functional null Snell’s waltzer (sv/sv) mice revealed that myosin VI is involved in kidney receptor-mediated endocytosis, a process which is important for preservation of protein and essential nutrients. To test whether Myo6gene has undergone an adaptive evolution in Old World fruit bats in relation to the preservation of protein and essential nutrients, we sequenced the coding region of Myo6gene in15bat 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). The molecular evolutionary analyses revealed a positive selection of Myo6gene along the ancestral branch of Old World fruit bats, however, no positive selection was detected on the ancestral branch leading to the New World fruit bats. And our results of Real-time PCR showed the highest expression level of Myo6gene in kidney among ten tissues examined in all three bat species, indicating an important role which this gene might involved in kidney. Our results strongly supported that Myo6gene has undergone an adaptive evolution in Old World fruit bats in relation to the receptor-mediated endocytosis for protein and essential nutrients preservation.