In photosynthetic organisms many processes are light dependent and sensing of light requires light-sensitive proteins. The supposed eyespot photoreceptor protein Babo1 (formerly Vop1) has previously been classified as an opsin due to the capacity for binding retinal. Here, we analyze Babo1 and provide evidence that it is no opsin. Due to the localization at the basal bodies, the former Vop1 and Cop1/2 proteins were renamed V.c. Babo1 and C.r. Babo1. We reveal a large family of more than 60 Babo1-related proteins from a wide range of species. The detailed subcellular localization of fluorescence-tagged Babo1 shows that it accumulates at the basal apparatus. More precisely, it is located predominantly at the basal bodies and to a lesser extent at the four strands of rootlet microtubules. We trace Babo1 during basal body separation and cell division. Dynamic structural rearrangements of Babo1 particularly occur right before the first cell division. In four-celled embryos Babo1 was exclusively found at the oldest basal bodies of the embryo and on the corresponding d-roots. The unequal distribution of Babo1 in four-celled embryos could be an integral part of a geometrical system in early embryogenesis, which establishes the anterior-posterior polarity and influences the spatial arrangement of all embryonic structures and characteristics. Due to its retinal-binding capacity, Babo1 could also be responsible for the unequal distribution of retinoids, knowing that such concentration gradients of retinoids can be essential for the correct patterning during embryogenesis of more complex organisms. Thus, our findings push the Babo1 research in another direction.

中文翻译：

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Babo1，以前是Vop1和Cop1 / 2，不是眼点光感受器，而是基体蛋白，阐明了Volvox Carteri中的细胞分裂。

在光合生物中，许多过程都依赖于光，并且感测光需要光敏蛋白。由于结合视网膜的能力，假定的眼点感光蛋白Babo1（以前称为Vop1）先前已归类为视蛋白。在这里，我们分析Babo1，并提供证据表明它不是视蛋白。由于位于基体，以前的Vop1和Cop1 / 2蛋白被重命名为Vc Babo1和Cr Babo1。我们揭示了一个大家族，包括来自多种物种的60多个与Babo1相关的蛋白质。带有荧光标签的Babo1的详细亚细胞定位表明，其在基底细胞中积累。更准确地说，它主要位于基体，在较小范围内位于小根微管的四股链上。我们在基础体分离和细胞分裂过程中追踪Babo1。Babo1的动态结构重排尤其发生在第一次细胞分裂之前。在四细胞胚胎中，Babo1仅存在于最古老的胚胎基体和相应的d根上。Babo1在四细胞胚胎中的不均等分布可能是早期胚胎发生中几何系统不可或缺的一部分，该几何系统建立了前后极性，并影响了所有胚胎结构和特征的空间排列。由于其视网膜结合能力，Babo1也可能是类维生素A分布不均的原因，因为知道类维生素A的这种浓度梯度对于更复杂生物体胚胎发生过程中的正确构图可能是必不可少的。因此，我们的发现将Babo1研究推向了另一个方向。