Department of Biological Science, Faculty of Life and Environmental Sciences, Shimane University, Japan.
Protist. 2013 Sep;164(5):660-72. doi: 10.1016/j.protis.2013.07.001. Epub 2013 Jul 31.
Paramecium bursaria harbor several hundred symbiotic Chlorella spp. Each alga is enclosed in a perialgal vacuole membrane, which can attach to the host cell cortex. How the perialgal vacuole attaches beneath the host cell cortex remains unknown. High-speed centrifugation (> 1000×g) for 1min induces rapid detachment of the algae from the host cell cortex and concentrates the algae to the posterior half of the host cell. Simultaneously, most of the host acidosomes and lysosomes accumulate in the anterior half of the host cell. Both the detached algae and the dislocated acidic vesicles recover their original positions by host cyclosis within 10min after centrifugation. These recoveries were inhibited if the host cytoplasmic streaming was arrested by nocodazole. Endosymbiotic algae during the early reinfection process also show the capability of desorption after centrifugation. These results demonstrate that adhesion of the perialgal vacuole beneath the host cell cortex is repeatedly inducible, and that host cytoplasmic streaming facilitates recovery of the algal attachment. This study is the first report to illuminate the mechanism of the induction to desorb for symbiotic algae and acidic vesicles, and will contribute to the understanding of the mechanism of algal and organelle arrangements in Paramecium.
嗜热四膜虫中含有数百种共生的绿球藻。每个藻类都被包裹在共生质体囊泡膜内，该囊泡膜可以附着在宿主细胞皮层上。然而，共生质体囊泡是如何附着在宿主细胞皮层下的，目前还不得而知。高速离心（>1000×g）1 分钟会诱导藻类迅速从宿主细胞皮层上脱离，并将藻类浓缩到宿主细胞的后半部分。同时，大多数宿主的液泡和溶酶体也积累在宿主细胞的前半部分。在离心后 10 分钟内，通过宿主胞质环流，无论是脱离的藻类还是移位的酸性囊泡都能恢复到原来的位置。如果用诺考达唑阻止宿主细胞质环流，则这些恢复过程会被抑制。在早期再感染过程中，内共生藻类也表现出离心后解吸的能力。这些结果表明，宿主细胞皮层下的共生质体囊泡的附着是可重复诱导的，而宿主细胞质环流有助于藻类附着的恢复。本研究首次揭示了共生藻类和酸性囊泡解吸的诱导机制，将有助于理解嗜热四膜虫中藻类和细胞器排列的机制。
