Kołowerzo-Lubnau Agnieszka, Niedojadło Janusz, Świdziński Michał, Bednarska-Kozakiewicz Elżbieta, Smoliński Dariusz J
Department of Cell Biology, Faculty of Biology and Environment Protection, Nicolaus Copernicus University, Toruń, Poland; Centre For Modern Interdisciplinary Technologies, Nicolaus Copernicus University, Toruń, Poland.
Department of Cell Biology, Faculty of Biology and Environment Protection, Nicolaus Copernicus University, Toruń, Poland.
PLoS One. 2015 Feb 11;10(2):e0117337. doi: 10.1371/journal.pone.0117337. eCollection 2015.
Manuscript provides insights into the biology of long-lived plants, different from Arabidopsis, tomato or grass species that are widely studied. In the European larch the diplotene stage lasts approximately 5 months and it is possible to divide it into several substages and to observe each of them in details. The diplotene stage is a period of intensive microsporocyte growth associated with the synthesis and accumulation of different RNA and proteins. Larch microsporocytes display changes in chromatin morphology during this stage, alternating between 4 short stages of chromatin condensation (contraction) and 5 longer diffusion (relaxation) stages. The occurrence of a diplotene diffusion stage has been observed in many plant species. Interestingly, they have also been observed during spermiogenesis and oogenesis in animals. The aim of this study was to examine whether chromatin relaxation during the diplotene is accompanied by the synthesis and maturation of mRNA. The results reveal a correlation between the diffusion and chromatin decondensation, transcriptional activity. We also found decreasing amount of poly(A) mRNA synthesis in the consecutive diffusion stages. During the early diffusion stages, mRNA is intensively synthesized. In the nuclei large amounts of RNA polymerase II, and high levels of snRNPs were observed. In the late diffusion stages, the synthesized mRNA is not directly subjected to translation but it is stored in the nucleus, and later transported to the cytoplasm and translated. In the last diffusion stage, the level of poly(A) RNA is low, but that of splicing factors is still high. It appears that the mRNA synthesized in early stages is used during the diplotene stage and is not transmitted to dyad and tetrads. In contrast, splicing factors accumulate and are most likely transmitted to the dyad and tetrads, where they are used after the resumption of intense transcription. Similar meiotic process were observed during oogenesis in animals. This indicates the existence of an evolutionarily conserved mechanism of chromatin-based regulation of gene expression during meiotic prophase I.
该手稿深入探讨了长寿植物的生物学特性，这些植物不同于广泛研究的拟南芥、番茄或禾本科植物。在欧洲落叶松中，双线期持续约5个月，并且可以将其分为几个亚阶段，并对每个亚阶段进行详细观察。双线期是一个微孢子母细胞大量生长的时期，与不同RNA和蛋白质的合成与积累相关。落叶松微孢子母细胞在此阶段染色质形态会发生变化，在4个短的染色质凝聚（收缩）阶段和5个较长的扩散（松弛）阶段之间交替。双线期扩散阶段在许多植物物种中都有观察到。有趣的是，在动物的精子发生和卵子发生过程中也观察到了它们。本研究的目的是检查双线期染色质松弛是否伴随着mRNA的合成和成熟。结果揭示了扩散与染色质解聚、转录活性之间的相关性。我们还发现在连续的扩散阶段，多聚腺苷酸mRNA合成量减少。在早期扩散阶段，mRNA大量合成。在细胞核中观察到大量的RNA聚合酶II和高水平的小核核糖核蛋白。在晚期扩散阶段，合成的mRNA不直接进行翻译，而是储存在细胞核中，随后运输到细胞质中进行翻译。在最后一个扩散阶段，多聚腺苷酸RNA水平较低，但剪接因子水平仍然较高。似乎在早期阶段合成的mRNA在双线期被利用，而不会传递到二分体和四分体。相反，剪接因子积累，最有可能传递到二分体和四分体，在强烈转录恢复后在那里被利用。在动物卵子发生过程中也观察到了类似的减数分裂过程。这表明在减数分裂前期I存在一种基于染色质的基因表达调控的进化保守机制。
