Department of Biological Science, University of Toronto (Scarborough), Scarborough, ON M1C 1A4, Canada.
Genome. 2013 Mar;56(3):139-45. doi: 10.1139/gen-2012-0157. Epub 2013 Mar 11.
We have found novel phenotypes for the previously studied Arabidopsis thaliana (L.) Heynh. meiotic mutant ahp2. These phenotypes were revealed by analysis of reconstructions of normal and ahp2 nuclei that were imaged using transmission electron microscopy. Previous studies of the ahp2 mutant demonstrated that it has a general failure to form synaptonemal complexes, except for the nucleolus organizing regions, and it fails to complete reciprocal genetic exchange. Here, we show that even though the ahp2 chromosome axes have only 5% of the normal amount of synaptonemal complex formation, it nonetheless has slightly more than 40% of the axes involved in close alignment. We also observed two striking nuclear envelope associated abnormalities. Wild type nuclei contain two nucleoli, one nucleolus-like structure, and nuclear envelope associated structures that we refer to as nuclear envelope associated disks. The ahp2 nuclei have the two nucleoli, but they lack the third nucleolus-like structure and instead have a previously uncharacterized structure that spans the nuclear envelope. Additionally, ahp2 meiocytes have nuclear envelope associated disks that are narrower and more numerous (∼2×) than those seen in wild type, and unlike the wild type disks, they are in direct contact with the nuclear envelope.
我们发现了先前研究的拟南芥（L.）Heynh 减数分裂突变体 ahp2 的新表型。这些表型是通过对使用透射电子显微镜成像的正常和 ahp2 核的重建进行分析揭示的。对 ahp2 突变体的先前研究表明，它普遍无法形成联会复合体，除了核仁组织区域，并且它无法完成相互遗传交换。在这里，我们表明，即使 ahp2 染色体轴只有正常联会复合体形成量的 5%，但它仍然有超过 40%的轴参与紧密排列。我们还观察到两个引人注目的核膜相关异常。野生型核包含两个核仁、一个类核仁结构和我们称为核膜相关盘的核膜相关结构。ahp2 核有两个核仁，但它们缺乏第三个类核仁结构，而是具有以前未表征的横跨核膜的结构。此外，ahp2 减数分裂细胞的核膜相关盘比野生型更窄且更多（约 2×），并且与野生型盘不同，它们与核膜直接接触。
