Spaethe Johannes, Briscoe Adriana D
Comparative and Evolutionary Physiology Group, Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA.
J Exp Biol. 2005 Jun;208(Pt 12):2347-61. doi: 10.1242/jeb.01634.
Ultraviolet-sensitive photoreceptors have been shown to be important for a variety of visual tasks performed by bees, such as orientation, color and polarization vision, yet little is known about their spatial distribution in the compound eye or optic lobe. We cloned and sequenced a UV opsin mRNA transcript from Bombus impatiens head-specific cDNA and, using western blot analysis, detected an eye protein band of approximately 41 kDa, corresponding to the predicted molecular mass of the encoded opsin. We then characterized UV opsin expression in the retina, ocelli and brain using immunocytochemistry. In the main retina, we found three different ommatidial types with respect to the number of UV opsin-expressing photoreceptor cells, namely ommatidia containing two, one or no UV opsin-immunoreactive cells. We also observed UV opsin expression in the ocelli. These results indicate that the cloned opsin probably encodes the P350 nm pigment, which was previously characterized by physiological recordings. Surprisingly, in addition to expression in the retina and ocelli, we found opsin expression in different parts of the brain. UV opsin immunoreactivity was detected in the proximal rim of the lamina adjacent to the first optic chiasm, which is where studies in other insects have found expression of proteins involved in the circadian clock, period and cryptochrome. We also found UV opsin immunoreactivity in the core region of the antennal lobe glomeruli and different clusters of perikarya within the protocerebrum, indicating a putative function of these brain regions, together with the lamina organ, in the entrainment of circadian rhythms. In order to test for a possible overlap of clock protein and UV opsin spatial expression, we also examined the expression of the period protein in these regions.
紫外线敏感光感受器已被证明对蜜蜂执行的各种视觉任务很重要，如定向、颜色和偏振视觉，但对于它们在复眼或视叶中的空间分布却知之甚少。我们从凤头蜂鸟头部特异性cDNA中克隆并测序了一种紫外线视蛋白mRNA转录本，并通过蛋白质免疫印迹分析检测到一条约41 kDa的眼蛋白条带，与编码视蛋白的预测分子量相对应。然后，我们使用免疫细胞化学方法对视网膜、单眼和大脑中的紫外线视蛋白表达进行了表征。在主视网膜中，我们发现了三种不同类型的小眼，其表达紫外线视蛋白的光感受器细胞数量不同，即含有两个、一个或没有紫外线视蛋白免疫反应性细胞的小眼。我们还观察到单眼中有紫外线视蛋白表达。这些结果表明，克隆的视蛋白可能编码P350 nm色素，该色素先前已通过生理记录进行了表征。令人惊讶的是，除了在视网膜和单眼中表达外，我们还在大脑的不同部位发现了视蛋白表达。在与第一视交叉相邻的神经纤维层近端边缘检测到紫外线视蛋白免疫反应性，在其他昆虫的研究中，这里发现了参与昼夜节律的蛋白质period和隐花色素的表达。我们还在触角叶神经纤维球的核心区域和原脑内不同的神经核团簇中发现了紫外线视蛋白免疫反应性，这表明这些脑区与神经纤维层器官一起在昼夜节律调节中可能具有假定功能。为了测试时钟蛋白和紫外线视蛋白空间表达是否可能重叠，我们还检查了这些区域中period蛋白的表达。
