Boyle L, O'Neill S L, Robertson H M, Karr T L
Department of Biochemistry, University of Illinois, Urbana 61801.
Science. 1993 Jun 18;260(5115):1796-9. doi: 10.1126/science.8511587.
Cytoplasmic incompatibility (CI) in Drosophila simulans is related to infection of the germ line by a rickettsial endosymbiont (genus Wolbachia). Wolbachia were transferred by microinjection of egg cytoplasm into uninfected eggs of both D. simulans and D. melanogaster to generate infected populations. Transinfected strains of D. melanogaster with lower densities of Wolbachia than the naturally infected D. simulans strain did not express high levels of CI. However, transinfected D. melanogaster egg cytoplasm, transferred back into D. simulans, generated infected populations that expressed CI at levels near those of the naturally infected strain. A transinfected D. melanogaster line selected for increased levels of CI expression also displayed increased symbiont densities. These data suggest that a threshold level of infection is required for normal expression of CI and that host factors help determine the density of the symbiont in the host.
拟果蝇中的细胞质不亲和性（CI）与一种立克次氏体胞内共生菌（沃尔巴克氏体属）对生殖系的感染有关。通过将卵细胞质显微注射到未感染的拟果蝇和黑腹果蝇的卵中，使沃尔巴克氏体得以转移，从而产生感染群体。与自然感染的拟果蝇菌株相比，沃尔巴克氏体密度较低的黑腹果蝇转染菌株并未表现出高水平的细胞质不亲和性。然而，将转染的黑腹果蝇卵细胞质再转移回拟果蝇中，所产生的感染群体表现出的细胞质不亲和性水平接近自然感染菌株。一个为提高细胞质不亲和性表达水平而选择的黑腹果蝇转染品系，其共生菌密度也有所增加。这些数据表明，细胞质不亲和性的正常表达需要达到一个感染阈值水平，并且宿主因素有助于决定共生菌在宿主体内的密度。
