Minaeva Ekaterina, Ermilova Elena
Laboratory Adaptation in Microorganisms, Biological Faculty, Saint-Petersburg State University, Universitetskaya em. 7/9, 199034, Saint-Petersburg, Russia.
Protoplasma. 2017 Jul;254(4):1769-1776. doi: 10.1007/s00709-016-1073-9. Epub 2017 Jan 11.
The unicellular green alga Chlorella variabilis NC64A is an endosymbiont of the ciliate Paramecium bursaria. The host's control, including the transfer of biochemical substrates from P. bursaria to C. variabilis, is involved in symbiotic relationships. C. variabilis NC64A that had been re-infected to P. bursaria for more than 1 year and isolated from the host showed higher chlorophyll levels compared to those in free-living cells. Unlike the host, the expression of C. variabilis NC64A heat shock 70 kDa protein was independent of establishment of endosymbiosis. In symbiotic cells, the levels of PII signal transduction protein (CvPII) that coordinate the central C/N anabolic metabolism were slightly higher than those in free-living cells. Furthermore, the environmental cues (light and host food bacteria availability) affected the abundance of CvPII, suggesting that synthesis of the protein was influenced by the host. Moreover, arginine concentrations in the symbiotic algae of P. bursaria were also controlled by the host's nutritional conditions. Together, our results imply that signal substrates and/or products of metabolism in host cells might act as messengers mediating the regulation of key events in symbiont cells.
单细胞绿藻可变小球藻NC64A是纤毛虫草履虫的内共生体。宿主的控制，包括从草履虫向可变小球藻的生化底物转移，参与了共生关系。重新感染草履虫1年以上并从宿主中分离出的可变小球藻NC64A，其叶绿素水平高于自由生活细胞中的叶绿素水平。与宿主不同，可变小球藻NC64A热休克70 kDa蛋白的表达与内共生的建立无关。在共生细胞中，协调中心碳/氮合成代谢的PII信号转导蛋白（CvPII）水平略高于自由生活细胞。此外，环境线索（光照和宿主食物细菌的可利用性）影响CvPII的丰度，表明该蛋白的合成受宿主影响。此外，草履虫共生藻类中的精氨酸浓度也受宿主营养条件的控制。总之，我们的结果表明，宿主细胞中信号底物和/或代谢产物可能作为信使介导共生体细胞中关键事件的调节。
