Sugino Ayu, Kobayashi Mayumi, Sugiura Mayumi, Harumoto Terue
Biological Sciences Course, Graduate School of Humanities and Sciences, Nara Women's University, Nara 630-8506, Japan.
Division of Science, Graduate School of Humanities and Sciences, Nara Women's University, Nara 630-8506, Japan.
Microorganisms. 2023 Jan 12;11(1):188. doi: 10.3390/microorganisms11010188.
In the genus Blepharisma, reproductive isolation between different species appears to be established at least by two barriers: (1) a mating pheromone, i.e., gamone 1, and (2) a factor involved in pair formation. Using four species, we experimentally investigated other potential barriers to interspecific conjugation in Blepharisma, as well as the first and second barriers. Cell-free fluid from type I cells (CFF1) of B. americanum had no effect on B. undulans, B. japonicum, or B. stoltei. Type II cells of B. americanum responded to CFF1 from B. americanum but not to CFF1 from B. undulans, B. japonicum, or B. stoltei. Gamone 1, therefore, seems to be the first reproductive barrier (with the inclusion of B. americanum species [megakaryotype 3]) as reported previously. In pretreated cells with complementary gamones in B. undulans and B. americanum, inter-species pair formation was rare, but pair formation between B. americanum and B. japonicum and between B. americanum and B. stoltei occurred at relatively high frequency. Most of the inter-species B. americanum−B. stoltei pairs underwent nuclear changes specific to conjugation. No significant difference was observed between the intra- and inter-species pairs over the time course of the nuclear changes, but the percentage of abnormal cells was higher in inter-species pairs than in intra-species pairs, and no progenies were produced by inter-species pairs. These results suggest a third barrier or step, in addition to the first and second ones, in nuclear changes after pair formation that prevents interspecific conjugation in Blepharisma.
在纤毛虫属中，不同物种之间的生殖隔离似乎至少由两个障碍建立：（1）一种交配信息素，即配子素1，以及（2）一个参与配对形成的因素。我们使用四个物种，对纤毛虫属种间接合的其他潜在障碍以及第一和第二障碍进行了实验研究。美洲大草履虫I型细胞的无细胞液（CFF1）对波动大草履虫、日本大草履虫或斯托尔大草履虫没有影响。美洲大草履虫的II型细胞对来自美洲大草履虫的CFF1有反应，但对来自波动大草履虫、日本大草履虫或斯托尔大草履虫的CFF1没有反应。因此，如先前报道的那样，配子素1似乎是第一个生殖障碍（包括美洲大草履虫物种[巨核型3]）。在用波动大草履虫和美洲大草履虫的互补配子素预处理的细胞中，种间配对很少见，但美洲大草履虫与日本大草履虫之间以及美洲大草履虫与斯托尔大草履虫之间的配对发生频率相对较高。大多数美洲大草履虫与斯托尔大草履虫的种间配对经历了接合特有的核变化。在核变化的时间过程中，种内和种间配对之间没有观察到显著差异，但种间配对中异常细胞的百分比高于种内配对，并且种间配对没有产生后代。这些结果表明，除了第一和第二个障碍之外，在配对形成后的核变化中还存在第三个障碍或步骤，这阻止了纤毛虫属中的种间接合。
