与基因组仅在单倍体和二倍体状态之间循环的经典观点相反,许多真核生物具有动态的基因组,在个体的整个生命周期中改变内容。然而,对微真核生物生命周期的一些详细研究使我们对真核生物基因组动力学的理解不完整。有孔虫(Rhizaria)具有重要的生态意义,然而研究不足,微生物真核生物进化枝,具有复杂的生命周期,包括倍性和基因组组织的变化。这里,我们将荧光显微镜和图像分析技术应用于110个细胞中的2,800多个细胞核,以表征Alogromialaticolaris菌株冷泉港(CSH)的生命周期,少数可培养的有孔虫之一。我们表明,单倍体和二倍体是拉氏弧菌生命周期中的短暂时刻,并且拉氏弧菌核内复制高达12,000倍的单倍体基因组大小。我们发现,A.laticollaris通过称为Zerfall的非规范机制将高度内复制的细胞核重组为数千个单倍体基因组,其中核包膜降解并将染色质挤出到细胞质中。基于这些发现,随着核结构在整个生命周期中的变化,我们认为拉氏A利用时空机制来描绘单个细胞核内的种系和体细胞DNA。这里的分析扩展了我们对整个真核生命树的基因组动力学的理解。重要在真核生物的传统描述中(即,有细胞核的细胞),生命周期只在单倍体和二倍体阶段之间交替,俯瞰不同微真核谱系的研究(例如,变形虫,纤毛虫,和鞭毛虫)在整个生命周期中显示出DNA含量的巨大变化。基因组的内复制使细胞能够生长到大尺寸,并且可能还响应于其环境的变化。很少有微真核生物生命周期被详细研究,这限制了我们对真核生物如何在世代之间调节和传递其DNA的理解。这里,我们用显微镜研究了拉氏菌株CSH的生命周期,有孔虫(主要是海洋变形虫的古老进化枝)中早期发散的谱系。我们证明了DNA含量在整个生命周期中都发生了显着变化,并进一步描述了一个不寻常的过程,称为Zerfall,通过这种方法,该物种将一个具有多达12,000个基因组拷贝的大核重组为数百个小配子核,每个都有一个单倍体基因组。我们的结果与以下观点一致:所有真核生物都划定种系DNA,以在更灵活的体细胞DNA中传递给后代,并延长真核生物生命周期的已知多样性。
In contrast to the canonical view that genomes cycle only between haploid and diploid states, many eukaryotes have dynamic genomes that change content throughout an individual\'s life cycle. However, the few detailed studies of microeukaryotic life cycles render our understanding of eukaryotic genome dynamism incomplete. Foraminifera (Rhizaria) are an ecologically important, yet understudied, clade of microbial eukaryotes with complex life cycles that include changes in ploidy and genome organization. Here, we apply fluorescence microscopy and image analysis techniques to over 2,800 nuclei in 110 cells to characterize the life cycle of Allogromia laticollaris strain Cold Spring Harbor (CSH), one of few cultivable foraminifera species. We show that haploidy and diploidy are brief moments in the A. laticollaris life cycle and that A. laticollaris nuclei endoreplicate up to 12,000 times the haploid genome size. We find that A. laticollaris reorganizes a highly endoreplicated nucleus into thousands of haploid genomes through a non-canonical mechanism called Zerfall, in which the nuclear envelope degrades and extrudes chromatin into the cytoplasm. Based on these findings, along with changes in nuclear architecture across the life cycle, we believe that A. laticollaris uses spatio-temporal mechanisms to delineate germline and somatic DNA within a single nucleus. The analyses here extend our understanding of the genome dynamics across the eukaryotic tree of life.IMPORTANCEIn traditional depictions of eukaryotes (i.e., cells with nuclei), life cycles alternate only between haploid and diploid phases, overlooking studies of diverse microeukaryotic lineages (e.g., amoebae, ciliates, and flagellates) that show dramatic variation in DNA content throughout their life cycles. Endoreplication of genomes enables cells to grow to large sizes and perhaps to also respond to changes in their environments. Few microeukaryotic life cycles have been studied in detail, which limits our understanding of how eukaryotes regulate and transmit their DNA across generations. Here, we use microscopy to study the life cycle of Allogromia laticollaris strain CSH, an early-diverging lineage within the Foraminifera (an ancient clade of predominantly marine amoebae). We show that DNA content changes significantly throughout their life cycle and further describe an unusual process called Zerfall, by which this species reorganizes a large nucleus with up to 12,000 genome copies into hundreds of small gametic nuclei, each with a single haploid genome. Our results are consistent with the idea that all eukaryotes demarcate germline DNA to pass on to offspring amidst more flexible somatic DNA and extend the known diversity of eukaryotic life cycles.