Villanueva Marco A, Barnay-Verdier Stéphanie, Priouzeau Fabrice, Furla Paola
Instituto de Ciencias del Mar y Limnología, Unidad Académica de Sistemas Arrecifales, Universidad Nacional Autónoma de México-UNAM, Prol. Avenida Niños Héroes S/N, 77580, Puerto Morelos, Quintana Roo, México,
Photosynth Res. 2015 Jun;124(3):305-13. doi: 10.1007/s11120-015-0142-9. Epub 2015 Apr 23.
The actin cytoskeleton is a dynamic structure that provides an interactive platform for organelles and cellular components. It also serves as track for membranes and vesicles that move via myosin. The actin cytoskeleton of Symbiodinium is a well-organized reticular structure suggestive of multiple membrane interactions, very likely including those of the chloroplast. The Symbiodinium chloroplast membrane network is, in turn, a highly organized structure, suggestive of being under the control of an organizing network. We visualized the chloroplast membranes of cultured Symbiodinium sp. under various light conditions and observed changes dependent on illumination intensity. Since we suspected interaction between these two organelles, and we knew that the Symbiodinium actin cytoskeleton collapses upon treatment with either latrunculin B, an actin microfilament-disrupting agent, or butanedione monoxime, a myosin function inhibitor, we tested the Symbiodinium sp. oxygen evolution in their presence. Upon latrunculin B addition, the oxygen production decreased compared to non-treated cells; however, this was not observed after a 24 h latrunculin treatment. On the contrary, butanedione monoxime treatment caused a non-recoverable dysfunction of the chloroplast causing a severe loss in oxygen production even after long-term exposure. Using electron microscopy, we observed an alteration of the Symbiodinium sp. chloroplast distribution after latrunculin B treatment, with respect to untreated cells. Furthermore, a thorough disorganization of the chloroplast grana was observed after butanedione monoxime treatment. These data suggest that an actomyosin system would be important for chloroplast organization and distribution, and critical for normal photosynthetic function of Symbiodinium sp.
肌动蛋白细胞骨架是一种动态结构，为细胞器和细胞组分提供了一个相互作用的平台。它还作为膜和囊泡通过肌球蛋白移动的轨道。共生藻的肌动蛋白细胞骨架是一种组织良好的网状结构，表明存在多种膜相互作用，很可能包括叶绿体的膜相互作用。反过来，共生藻的叶绿体膜网络是一种高度组织化的结构，表明受一个组织网络的控制。我们在各种光照条件下观察了培养的共生藻的叶绿体膜，并观察到依赖于光照强度的变化。由于我们怀疑这两个细胞器之间存在相互作用，而且我们知道用肌动蛋白微丝破坏剂拉特兰菌素B或肌球蛋白功能抑制剂丁二酮肟处理后，共生藻的肌动蛋白细胞骨架会解体，因此我们测试了共生藻在它们存在时的放氧量。添加拉特兰菌素B后，与未处理的细胞相比，氧气产量下降；然而，在拉特兰菌素处理24小时后未观察到这种情况。相反，丁二酮肟处理导致叶绿体出现不可恢复的功能障碍，即使在长期暴露后氧气产量也严重下降。使用电子显微镜，我们观察到与未处理的细胞相比，拉特兰菌素B处理后共生藻的叶绿体分布发生了改变。此外，在丁二酮肟处理后观察到叶绿体基粒完全紊乱。这些数据表明，肌动球蛋白系统对叶绿体的组织和分布很重要，对共生藻的正常光合功能至关重要。
