Wernet Mathias F, Labhart Thomas, Baumann Franziska, Mazzoni Esteban O, Pichaud Franck, Desplan Claude
New York University, Department of Biology, 100 Washington Square East, New York, NY 10003, USA.
Cell. 2003 Oct 31;115(3):267-79. doi: 10.1016/s0092-8674(03)00848-1.
Different classes of photoreceptors (PRs) allow animals to perceive various types of visual information. In the Drosophila eye, the outer PRs of each ommatidium are involved in motion detection while the inner PRs mediate color vision. In addition, flies use a specialized class of inner PRs in the "dorsal rim area" of the eye (DRA) to detect the e-vector of polarized light, allowing them to exploit skylight polarization for orientation. We show that homothorax is both necessary and sufficient for inner PRs to adopt the polarization-sensitive DRA fate instead of the color-sensitive default state. Homothorax increases rhabdomere size and uncouples R7-R8 communication to allow both cells to express the same opsin rather than different ones as required for color vision. Homothorax expression is induced by the iroquois complex and the wingless (wg) pathway. However, crucial wg pathway components are not required, suggesting that additional signals are involved.
不同类型的光感受器（PRs）使动物能够感知各种视觉信息。在果蝇眼中，每个小眼的外部光感受器参与运动检测，而内部光感受器介导颜色视觉。此外，果蝇利用眼睛“背缘区域”（DRA）中一类特殊的内部光感受器来检测偏振光的电场矢量，使它们能够利用天空光偏振进行定向。我们发现，同源胸节对于内部光感受器采用偏振敏感的DRA命运而非颜色敏感的默认状态既必要又充分。同源胸节增加了视杆的大小，并解除了R7 - R8之间的通信，使两个细胞都能表达相同的视蛋白，而不是颜色视觉所需的不同视蛋白。同源胸节的表达由伊洛魁族复合体和无翅（wg）信号通路诱导。然而，关键的wg信号通路成分并非必需，这表明还有其他信号参与其中。
