Evolution and expression of the phosphodiesterase 6 genes unveils vertebrate novelty to control photosensitivity

Background: Phosphodiesterase 6 (PDE6) is a protein complex that hydrolyses cGMP and acts as the effector of the vertebrate phototransduction cascade. The PDE6 holoenzyme consists of catalytic and inhibitory subunits belonging to two unrelated gene families. Rods and cones express distinct genes from both families: PDE6A and PDE6B code for the catalytic and PDE6G the inhibitory subunits in rods while PDE6C codes for the catalytic and PDE6H the inhibitory subunits in cones. We performed phylogenetic and comparative synteny analyses for both gene families in genomes from a broad range of animals. Furthermore, gene expression was investigated in zebrafish. Results: We found that both gene families expanded from one to three members in the two rounds of genome doubling (2R) that occurred at the base of vertebrate evolution. The PDE6 inhibitory subunit gene family appears to be unique to vertebrates and expanded further after the teleost-specific genome doubling (3R). We also describe a new...背景：磷酸二酯酶6（Phosphodiesterase 6, PDE6）是一类可水解环磷酸鸟苷（cGMP）的蛋白质复合物，作为脊椎动物光转导级联反应的效应分子发挥功能。PDE6全酶由隶属于两个不相关基因家族的催化亚基与抑制亚基组成。视杆细胞与视锥细胞分别表达两个家族的不同基因：视杆中，PDE6A与PDE6B编码催化亚基，PDE6G编码抑制亚基；视锥中，PDE6C编码催化亚基，PDE6H编码抑制亚基。本研究对广泛动物类群的基因组开展了两个基因家族的系统发育与比较同线性分析，并对斑马鱼中的基因表达情况进行了检测。结果：本研究发现，在脊椎动物演化起源处发生的两轮基因组复制（2R）过程中，两个基因家族均从1个成员扩增至3个成员。PDE6抑制亚基基因家族似乎为脊椎动物所特有，并在硬骨鱼特异性基因组复制（3R）后进一步发生扩增。此外，本研究还报道了一个新的……