Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Headley Way, Oxford OX3 9DU, UK.
Mol Ecol. 2012 Jul;21(13):3121-58. doi: 10.1111/j.1365-294X.2012.05617.x. Epub 2012 May 31.
In craniates, opsin-based photopigments expressed in the eye encode molecular 'light sensors' that constitute the initial protein in photoreception and the activation of the phototransduction cascade. Since the cloning and sequencing of the first vertebrate opsin gene (bovine rod opsin) nearly 30 years ago (Ovchinnikov Yu 1982, FEBS Letters, 148, 179-191; Hargrave et al. 1983, Biophysics of Structure & Mechanism, 9, 235-244; Nathans & Hogness 1983, Cell, 34, 807-814), it is now well established that variation in the subtypes and spectral properties of the visual pigments that mediate colour and dim-light vision is a prevalent mechanism for the molecular adaptation to diverse light environments. In this review, we discuss the origins and spectral tuning of photopigments that first arose in the agnathans to sample light within the ancient aquatic landscape of the Early Cambrian, detailing the molecular changes that subsequently occurred in each of the opsin classes independently within the main branches of extant jawed gnathostomes. Specifically, we discuss the adaptive changes that have occurred in the photoreceptors of craniates as they met the ecological challenges to survive in quite differing photic niches, including brightly lit aquatic surroundings; the deep sea; the transition to and from land; diurnal, crepuscular and nocturnal environments; and light-restricted fossorial settings. The review ends with a discussion of the limitations inherent to the 'nocturnal-bottleneck' hypothesis relevant to the evolution of the mammalian visual system and a proposition that transition through a 'mesopic-bottleneck' may be a more appropriate model.
在有头类动物中，眼睛中表达的视蛋白基光感受器编码构成光感受和光转导级联激活的初始蛋白的分子“光传感器”。自从近 30 年前（Ovchinnikov Yu 1982，FEBS Letters，148，179-191；Hargrave 等人，1983，结构与机制生物物理学，9，235-244；Nathans 和 Hogness，1983，细胞，34，807-814）克隆和测序了第一个脊椎动物视蛋白基因（牛视杆蛋白）以来，现在已经很清楚，介导颜色和弱光视觉的视色素的亚型和光谱特性的变化是分子适应不同光环境的普遍机制。在这篇综述中，我们讨论了在无颌类中首次出现的光感受器的起源和光谱调谐，以在早期寒武纪的古老水生景观中采样光，详细介绍了随后在现存有颌类动物的主要分支中独立发生的每个视蛋白类别的分子变化。具体来说，我们讨论了脊椎动物感光器发生的适应性变化，因为它们在不同的光环境中生存面临着生态挑战，包括明亮的水生环境；深海；从海洋到陆地的过渡；昼夜、黄昏和夜间环境；以及受限制的穴居环境。综述以讨论与哺乳动物视觉系统进化相关的“夜间瓶颈”假说所固有的局限性以及通过“中间光瓶颈”过渡可能是一个更合适的模型结束。
