Spectral differentiation of blue opsins between phylogenetically close but ecologically distant goldfish and zebrafish
Spectral differentiation of blue opsins between phylogenetically close but ecologically distant goldfish and zebrafish
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DOI：
10.1074/jbc.m413001200
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发表时间：
2005-03-11
影响因子：
4.8
通讯作者：
Kawamura, S
中科院分区：
文献类型：
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作者：
Chinen, A;Matsumoto, Y;Kawamura, S
斑马鱼和金鱼都是同属鲤科的白天活动的淡水鱼，但它们的视觉生态环境有很大的不同。斑马鱼是以宽和短波为主的背景光谱条件下的水面游泳者，而金鱼是广义的游泳者，其光环境随着浑浊而延伸到短波吸收增加的深度。斑马鱼蓝(SWS2)视觉色素的峰值吸收光谱(最大吸收波长)与金鱼视觉色素的吸收光谱(443 Nm)相比一致向短波长(416 Nm)移动。在两种色素之间的氨基酸差异中，只有一种(斑马鱼中的丙氨酸和金鱼中的丝氨酸在第94位残基)会导致吸收光谱的不同(Newt SWS2的14 nm波长(Max)移动)。在这项研究中，我们通过应用基于似然的贝叶斯统计和进行定点突变来重建这两个物种的祖先SWS2色素。重组的祖先光致变色的最大吸收波长为430 nm，表明斑马鱼和金鱼分别从祖先获得了短波长(-14 nm)和长波长(+13 nm)的光谱位移。出乎意料的是，当S94A突变被引入到金鱼SWS2色素中时，只导致了-3 nm的光谱漂移。T116L(6 Nm)取代了金鱼色素近一半的长波移位。斑马鱼SWS2的S295C突变有助于在400 nm左右产生吸收峰，并扩大其在短波长方向的光谱灵敏度。这些结果表明，进化工程方法在解释视觉色素功能分化过程中是非常有效的。
Zebrafish and goldfish are both diurnal freshwater fish species belonging to the same family, Cyprinidae, but their visual ecological surroundings considerably differ. Zebrafish are surface swimmers in conditions of broad and shortwave-dominated background spectra and goldfish are generalized swimmers whose light environment extends to a depth of elevated short wavelength absorbance with turbidity. The peak absorption spectrum (lambda(max)) of the zebrafish blue (SWS2) visual pigment is consistently shifted to short wavelength (416 nm) compared with that of the goldfish SWS2 (443 nm). Among the amino acid differences between the two pigments, only one (alanine in zebrafish and serine in goldfish at residue 94) was previously known to cause a difference in absorption spectrum (14-nm lambda(max) shift in newt SWS2). In this study, we reconstructed the ancestral SWS2 pigment of the two species by applying likelihood-based Bayesian statistics and performing site-directed mutagenesis. The reconstituted ancestral photopigment had a lambda(max) of 430 nm, indicating that zebrafish and goldfish achieved short wavelength (-14 nm) and long wavelength (+13 nm) spectral shifts, respectively, from the ancestor. Unexpectedly, the S94A mutation resulted in only a -3-nm spectral shift when introduced into the goldfish SWS2 pigment. Nearly half of the long wavelength shift toward the goldfish pigment was achieved instead by T116L (6 nm). The S295C mutation toward zebrafish SWS2 contributed to creating a ridge of absorbance around 400 nm and broadening its spectral sensitivity in the short wavelength direction. These results indicate that the evolutionary engineering approach is very effective in deciphering the process of functional divergence of visual pigments.