Abstract
The molecular basis of the evolution of phenotypic characters is very complex and is poorly understood with few examples documenting the roles of multiple genes. Considering that a single gene cannot fully explain the convergence of phenotypic characters, we choose to study the convergent evolution of rod vision in two divergent bats from a network perspective. The Old World fruit bats (Pteropodidae) are non-echolocating and have binocular vision, whereas the sheath-tailed bats (Emballonuridae) are echolocating and have monocular vision; however, they both have relatively large eyes and rely more on rod vision to find food and navigate in the night. We found that the genes CRX, which plays an essential role in the differentiation of photoreceptor cells, SAG, which is involved in the desensitization of the photoactivated transduction cascade, and the photoreceptor gene RH, which is directly responsible for the perception of dim light, have undergone parallel sequence evolution in two divergent lineages of bats with larger eyes (Pteropodidae and Emballonuroidea). The multiple convergent events in the network of genes essential for rod vision is a rare phenomenon that illustrates the importance of investigating pathways and networks in the evolution of the molecular basis of phenotypic convergence.
Highlights
Independent convergent evolution of phenotypic characters in response to similar selective pressures is not rare, the molecular basis of these phenomena are poorly known [1,2]
A previous study indicated that convergent evolution in rhodopsin (RH1), a rod vision gene that encodes the pigment directly responsible for the perception of dim light [20], had occurred in Pteropodidae and Emballonuridae [5]
CRX regulates the expression of many rod vision-specific genes [22], and mutations in this gene cause autosomal dominant cone-rod dystrophy [23], autosomal dominant retinitis pigmentosa [24] and Leber’s congenital amaurosis [25,26]
Summary
Independent convergent evolution of phenotypic characters in response to similar selective pressures is not rare, the molecular basis of these phenomena are poorly known [1,2]. A previous study indicated that convergent evolution in rhodopsin (RH1), a rod vision gene that encodes the pigment directly responsible for the perception of dim light [20], had occurred in Pteropodidae and Emballonuridae [5]. CRX regulates the expression of many rod vision-specific genes [22], and mutations in this gene cause autosomal dominant cone-rod dystrophy [23], autosomal dominant retinitis pigmentosa [24] and Leber’s congenital amaurosis [25,26] Another gene involved in rod vision is SAG, which encodes S-arrestin protein, a major soluble photoreceptor protein that is involved in the desensitization of the photoactivated transduction cascade. While RH1 is essential for perception in dim light, CRX and SAG are of critical importance for the function of photoreceptor cells and the animal’s ability to adapt to dim light
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