冬去春来，白昼在不知不觉中变得越来越长。人类可能不会察觉这些微妙的细节，然而鸟类却无时无刻不在监视着这些细微的变化。
据美国《科学》杂志在线新闻报道，研究人员发现，鸟类通过监控季节的变化来知晓何时应该交配。如今，经过几十年的研究，研究人员报告说，他们终于确定了一种能够让鸟类知道春天来了的蛋白质——脊椎动物远古视蛋白（VA opsin）。由它在大脑中形成的感光器对于图中这只知更鸟的成功繁殖是至关重要的。研究人员在上周的《现代生物学》杂志网络版上报告了这一发现。（生物谷Bioon.com）
生物谷推荐原始出处：
Current Biology, 06 August 2009 doi:10.1016/j.cub.2009.06.066
VA Opsin-Based Photoreceptors in the Hypothalamus of Birds
Stephanie Halford1,3,Susana S. Pires1,3,Michael Turton1,Lei Zheng1,Irene González-Menéndez2,Wayne L. Davies1,Stuart N. Peirson1,José M. García-Fernández2,Mark W. Hankins1,,andRussell G. Foster1,,
1 Circadian and Visual Neuroscience, Nuffield Laboratory of Ophthalmology, University of Oxford, Headley Way, Oxford OX3 9DU, UK
2 Departamento de Morfología y Biología Celular, Universidad de Oviedo, 33006 Oviedo, Spain
Studies in the 1930s demonstrated that birds possess photoreceptors that are located within the hypothalamus and regulate photoperiodic responses to day length [1,2]. Most recently, photoperiod has been shown to alter the activity of the pars tuberalis to release thyrotrophin, which ultimately drives a reproductive response [3,4]. Despite these significant findings, the cellular and molecular identity of the hypothalamic photoreceptors has remained a mystery. Action spectra implicated an opsin-based photopigment system [5], but further identification based on rod- or cone-opsin probes failed, suggesting the utilization of a novel opsin [6]. The vertebrate ancient (VA) opsin photopigments were isolated in 1997 [7,8] but were thought to havea restricted taxonomic distribution, confined to the agnatha and teleost fish. Here, we report the isolation of VA opsin from chicken and show that the two isoforms spliced from this gene (cVAL and cVA) are capable of forming functional photopigments. Further, we show that VA opsin is expressed within a population of hypothalamic neurons with extensive projections to the median eminence. These results provide the most complete cellular and molecular description of a deep brain photoreceptor in any vertebrate and strongly implicate VA opsin in mediating the avian photoperiodic response.
