Opsins in the Cephalic and Extracephalic Photoreceptors in the Marine Gastropod Onchidium verruculatum
Opsins in the Cephalic and Extracephalic Photoreceptors in the Marine Gastropod Onchidium verruculatum
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DOI：
10.1086/723013
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发表时间：
2022-12-01
影响因子：
1.6
通讯作者：
Nishi，Takako
中科院分区：
文献类型：
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作者：
Matsuo，Ryota;Kotoh，Sanae;Nishi，Takako
海洋腹足类Onchidium verruculatum在其靠近头部的柄尖端上具有一对视觉感光器，即柄眼，以及几个脑外感光器官。柄眼的视网膜由两种形态上不同的视细胞组成，即具有发达微绒毛的I型细胞和具有不发达微绒毛的II型细胞。脑外光感受器包括背侧眼、皮肤光感受器和脑光敏神经元。这些头和头外感光器官的特点已从形态学和电生理学的角度进行了研究。然而，人们对这些器官中负责光检测的视觉色素分子知之甚少。在本研究中，我们寻找了在石鳖神经组织中表达的视蛋白分子，并鉴定了六种推定的具有信号转导能力的视蛋白，包括Xenopsin 1，Xenopsin 2，Gq-偶联视紫红质1，Gq-偶联视紫红质2，Opsin-5 B和Gq-偶联视紫红质样。免疫组织化学染色的六个视蛋白中的四个显示，Xenopsin 1，Gq-耦合视紫红质1，和Gq-耦合视紫红质2中的柄眼的横纹肌和皮肤感光细胞中表达。Xenopsin 2在柄眼的II型光感受器和背侧眼的睫状光感受器中表达。这些免疫组化数据与定量逆转录聚合酶链反应显示的表达分析结果一致。本研究阐明了石鳖脑外光感受器中视蛋白表达的特性及不同光感受器的分子组成。
The marine gastropodOnchidium verruculatumhas a pair of ocular photoreceptors, the stalk eyes, on the tip of its stalk near the head, as well as several extracephalic photosensory organs. The retinas of the stalk eye consist of two morphologically distinct visual cells, namely, the type I cells equipped with well-developed microvilli and the type II cells with less developed microvilli. The extracephalic photosensors comprise the dorsal eye, dermal photoreceptor, and brain photosensitive neurons. The characteristics of these cephalic and extracephalic photosensory organs have been studied from morphological and electrophysiological perspectives. However, little is known about the visual pigment molecules responsible for light detection in these organs. In the present study, we searched for opsin molecules that are expressed in the neural tissues ofOnchidiumand identified six putative signaling-competent opsin species, including Xenopsin1, Xenopsin2, Gq-coupled rhodopsin1, Gq-coupled rhodopsin2, Opsin-5B, and Gq-coupled rhodopsin-like. Immunohistochemical staining of four of the six opsins revealed that Xenopsin1, Gq-coupled rhodopsin1, and Gq-coupled rhodopsin2 are expressed in the rhabdomere of the stalk eye and in the dermal photoreceptor. Xenopsin2 was expressed in the type II photoreceptors of the stalk eye and in the ciliary photoreceptors of the dorsal eye. These immunohistochemical data were consistent with the results of the expression analysis, revealed by quantitative reverse transcription polymerase chain reaction. This study clarified the identities of opsins expressed in the extracephalic photosensory organs ofOnchidiumand the distinct molecular compositions among the photoreceptors.