Control of Organelle Inheritance

本研究为莱茵衣藻细胞器DNA单倍体遗传的分子机制提供了详细的认识。莱茵松子质体基因组的单代遗传涉及两个事件：交配型+ (mt+)配子对受精卵的染色体保护和受精卵中未受保护的mt-染色体的核酸酶破坏。与两个mt位点相连的克隆基因簇ezy-1已被该实验室证明参与了破坏。使用天然和/或重组ezy-1蛋白的实验旨在了解ezy-1是否作为核酸酶或作为核酸酶活性的激活剂。遗传和生化实验将确定保护是直接授予mt+叶绿体DNA（例如通过甲基化）还是通过与该DNA相关的蛋白质。最后，寻找和分析保护缺陷的插入突变株。真核生物是由含有细胞器的细胞组成的。其中，线粒体（动物和植物）和叶绿体（仅植物）含有它们自己的DNA互补体，这些DNA来源于它们作为自由生活细菌的进化起源。在有性生殖过程中，细胞器DNA总是只通过一个亲本传递给后代，通常是通过母性卵子。在单细胞藻类衣藻中，两个亲本配子向受精卵提供等量的细胞器DNA，但其中一组随后被破坏。该实验室已经克隆了一个基因，其蛋白质产物似乎参与了叶绿体DNA的这种选择性降解。该项目建议通过基因、分子和细胞生物学实验来验证这一推断，目的是了解在单个细胞中，一组亲本DNA是如何被破坏而另一组DNA是如何被保存下来的。＊＊＊

9319595 Goodenough The research proposed would provide detailed molecular understanding of the mechanisms of uniparental inheritance of organelle DNA in Chlamydomonas reinhardtii. Uniparental inheritance of the plastid genome in C. reinhardtii involved two events: protection of the chromosome contributed to the zygote by the mating-type plus (mt+) gamete, and nuclease destruction of the unprotected mt- chromosome in the zygote. A cloned gene cluster, ezy-1 linked to both mt loci, has been shown by this lab to be involved in destruction. Experiments using native and/or recombinant ezy-1 protein are designed to learn whether ezy-1 functions as the nuclease or as an activator of nuclease activity. Genetic and biochemical experiments will determine whether protection is conferred directly on the mt+ chloroplast DNA (e.g. via methylation) or via protein(s) that associate with this DNA. And finally, insertional mutant strains defective in protection will be sought and analyzed. %%% Eukaryotic organisms are composed of cells that contain organelles. Of these, mitochondria (animals and plants) and chloroplast (plants only) contain their own complements of DNA, derived from their evolutionary origin as free-living bacteria. During sexual reproduction, organelle DNA is invariably transmitted to offspring via only one parent, usually via the maternal egg. In the unicellular alga Chlamydomonas, both parental gametes contribute equal amounts of organelle DNA to the zygote, but one set is then destroyed. The lab has cloned a gene whose protein product appears to participate in this selective degradation of chloroplast DNA. The project proposes to test this inference via genetic, molecular, and cell biology experiments, the goal being to learn how one parental set of DNA is destroyed and the other is preserved within a single cell. ***