Analysis apaptosis phenomena of nuclei in zygospores of Phycomyces

当两种交配类型交配时，藻类是多核的，数千个核从亲本配子囊转移到合子孢子中。然而，只有一两个二倍体细胞核能够存活到约6个月的休眠期结束。其余残存的核随着合子孢子年龄的增加而丧失功能并逐渐消失。为了探讨这种核细胞凋亡现象的机制，我们观察了合子孢子的特性随年龄的变化。交配后第10天合子孢子的物理硬度增加，约为交配后第10天前合子孢子的5倍。合子孢子萌发前硬度恢复到正常水平。第10天后合子孢子的另一个特征是中央出现一个大油滴。萌发前油滴也消失了。再生…的孢子囊和菌丝上发育的孢子中核的遗传分析从不同年龄切开的合子孢子上的更多结果表明，减数分裂在交配后第10天才完成。在第10天后，没有出现任何结构的再生。选择具有不同遗传标记的异核亲本之间形成的合孢子，并将它们的原生质(包括核)转移到一个营养缺陷型突变体的孢子囊柄片段中。对再生植株在孢子囊切段上的遗传标记重组的孢子分析表明，减数分裂发生在配对后第30天左右。光镜和电子显微镜观察显示，交配后第7-8天，细胞核体积增大，第10天至第20天，细胞核体积急剧减少。30d后，老化合子孢子内可见部分变性核聚集。胞膜破裂的胞核也可见。这些发现表明，除了存活的二倍体核(EI)外，所有的核在交配后10天都失去了功能。较少

Phycomyces is multinucleate and thousands of nuclei transfer from parental gametangia into zygospores when two mating types were mated. Only one or two diploid nuclei, however, are able to survive until the end of the dormancy period of about 6 months. The other remained nuclei lose their functions and gradually disappear with an increase in the age of zygospores. To explore the mechanisms of this apaptosis phenomenon of nuclei, the zygospores were inspected for the age-dependent changes of their characteristics.1. The zygospores increased in their physical hardness after the 10th day of the mating, about 5 times harder than the zygospores before 10 days after mating. The hardness recovered to the normal just before the zygospore germination. Emergence of a large central oil-drop is another characteristic of the post-10th-day zygospores. The oil drop also disappeared before the germination.2. Genetic analyses of nuclei in the spores developed on sporangiophores and hyphae which regener … More ated from the incised zygospores with different ages revealed that meiosis has not completed before 10th day after mating. No regeneration of any structures occurred on the post-10th day zygospores.3. The zygospores formed between the heterokaryotic parents with several different genetic markers were selected and their protoplasm including nuclei were transferred into the sporangiophore segments of an auxotropic mutant. The spore analysis for recombination of genetic markers of the regenerants on the sporangiophore segments implied that meiosis occurred in the zygospores around 30th day after the mating.4. Microscopic and electromicroscopic observations revealed that the nuclei increased in their volumes at the 7-8th days after mating but sharply decreased after the 10th day till the 20th day.5. Aggregation of some degenerated nuclei was found in the aged zygospores after the 30th day. Nuclei with broken membrane were also found. These findings imply that all the nuclei except for the survive diploid nucleus(ei) lose their functions 10 days after mating. Less