Department of Plant Breeding and Genetics, Cornell University, Ithaca, NY 14853, USA.
Proc Natl Acad Sci U S A. 2009 Dec 8;106(49):20989-94. doi: 10.1073/pnas.0906498106. Epub 2009 Nov 19.
The ability of chromosomes to move across the nuclear space is essential for the reorganization of the nucleus that takes place in early meiotic prophase. Chromosome dynamics of prophase I have been studied in budding and fission yeasts, but little is known about this process in higher eukaryotes, where genomes and chromosomes are much larger and meiosis takes a longer time to complete. This knowledge gap has been mainly caused by difficulties in culturing isolated live meiocytes of multicellular eukaryotes. To study the nuclear dynamics during meiotic prophase in maize, we established a system to observe live meiocytes inside intact anthers. We found that maize chromosomes exhibited extremely dynamic and complex motility in zygonema and pachynema. The movement patterns differed dramatically between the two stages. Chromosome movements included rotations of the entire chromatin and movements of individual chromosome segments, which were mostly telomere-led. Chromosome motility was coincident with dynamic deformations of the nuclear envelope. Both, chromosome and nuclear envelope motility depended on actin microfilaments as well as tubulin. The complexity of the nuclear movements implies that several different mechanisms affect chromosome motility in early meiotic prophase in maize. We propose that the vigorous nuclear motility provides a mechanism for homologous loci to find each other during zygonema.
染色体在核空间中移动的能力对于早期减数分裂前期发生的核重排至关重要。 有丝分裂前期的染色体动力学已在出芽酵母和裂殖酵母中进行了研究，但对于基因组和染色体大得多且减数分裂完成时间更长的高等真核生物，对此过程知之甚少。 造成这种知识差距的主要原因是培养多细胞真核生物分离的活减数分裂细胞的困难。 为了研究玉米减数分裂前期的核动态，我们建立了一个在完整花药内观察活减数分裂细胞的系统。 我们发现玉米染色体在细线期和粗线期表现出极其动态和复杂的运动。 这两个阶段的运动模式有很大的不同。 染色体运动包括整个染色质的旋转和单个染色体片段的运动，这些运动主要由端粒引导。 染色体运动与核膜的动态变形一致。 染色体和核膜的运动都依赖于肌动蛋白微丝和微管。 核运动的复杂性意味着有几种不同的机制影响玉米减数分裂前期的染色体运动。 我们提出，强烈的核运动为同源基因座在细线期找到彼此提供了一种机制。
