冠突伪尾柱虫有性生殖期间皮膜发育的核控制

通过显微手术去小核建立多个冠突伪尾柱虫（Pseudourostyla cristata)无小细胞系，并诱导它们与有小核细胞进行接合生殖，以评估小核及其衍生的大核原基在有性生殖期间对皮膜形态发生的影响，当无小核接合体从有小核配偶获得1枚配子核后，接合双方不仅能平行地继续核器演化，而且使第1次皮膜改组能够同步进行和正常发育，说明小核在有性周期中除了生殖功能外仍保留着某些控制皮膜发育的体功能，虽然大部分接合后体的大核原基在DNA贫乏期停止发育，但少数接合后体能够超越这一时期，并启动第2次皮膜改组和顺利完成其后续的有性发育全程，表明指令发动第2次皮膜发育的信号来自DNA贫乏期后以排出一核物质团块为标志的大核原基。

Nuclear Control of Cortical Development during Conjugation in Pseudourostyla cristata

Amicronucleate cell lines of the ciliated protozoan Pseudourostyla cristata from different mating types are generated by microsurgery. With a rescue conjugating amicronucleates with micronucleates，the sexual development of conjugants and exconjugants becomes more normal than that in conjugation among amicronucleates. The first cortical reorganization proceeds as usual to generate a set of incomplete ciliature，but the membranelle number of adoral zone of membranelles (AZM) and the number of frontal-ventral-transverse cirri (FVT) approach those in conjugation among micronucleates，and differentiation and positioning of the ciliature appear normally. It is evident that the micronucleus is important for maintaining regular development of the first cortical reorganization. During conjugation，a male gametic nucleus from the micronucleate mate migrates into its amicronucleate partner and a female gametic nucleus stays in situ，the haploid gametic nucleus in both conjugants transforms into a hemizygote without fertilization. After twice post-hemizygote division，a new micronucleus and a macronuclear anlage are generated as usual. The macronuclear anlage develops through chromosome polytenization，fragmentation，genome rearrangement and DNA-poor stages. However，in most exconjugants，development of the macronuclear anlage becomes arrested before the next stage when a vacuolated and DNA-poor mass forms and then is extruded from the anlage，and thereafter the anlage turns pycnotic. The second cortical reorganization could not be initiated in such cells. But in a few others (about 10% exconjugants) of some specific mating combinations in which the young micronucleate cell line (28 or 46) is micronuclear donor for nucleogenesis，the macronuclear anlage can develop beyond the stage，and the cells can undergo the second，and then the third and the fourth round of cortical reorganization. After the sexual development，the cell transforms into asexual cycle and a viable clone is produced. The correlation between macronuclear anlage development and initiation of the second cortical reorganization suggests that the crucial morphogenetic signal to trigger the second morhpogenesis is provided by the macronuclear anlage which has developed beyond the post-polyteny DNA-poor stage.