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首页> 外文期刊>Protoplasma: An International Journal of Cell Biology >Origin of facultative heterochromatin in the endosperm of Gagea lutea (Liliaceae)
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Origin of facultative heterochromatin in the endosperm of Gagea lutea (Liliaceae)

机译：Gagea lutea（紫ilia科）的胚乳中兼性异染色质的起源

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摘要

Facultative heterochromatin occurs not only in certain animals in connection with sex determination but also in members of at least one plant genus, Gagea (Liliaceae s. str.), but here in the course of embryo sac development, fertilization, and endosperm formation. The present contribution intends to provide undebatable photographic and cytometric evidence, previously not available, for the events in the course of which three whole genomes in the pentaploid endosperm nuclei of Gagea lutea become heterochromatinized, In this plant, embryo sac formation usually follows the Fritillaria type, i.e., the embryo sac is tetrasporic, and a "1 + 3 position" of the spore nuclei is followed by a mitosis in which the three chalazal spindles fuse and two triploid nuclei are formed. A triploid chalazal polar nucleus is derived from one of these, which contributes to the pentaploid endosperm. These nuclei in the chalazal part of the embryo sac show stronger condensation compared with the micropylar ones. The pyenosis of the triploid polar nucleus is maintained and even enhanced during endosperm proliferation, while the micropylar polar nucleus and the sperm nucleus maintain their euchromatic condition. The origin of the heterochromatic masses in the endosperm nuclei from the three chalazal genomes of the central cell is unambiguously evident from the distribution of heterochromatic chromosomes in the first endosperm mitosis and the following interphase. DNA content measurements confirm a 3 : 2 relationship of heterochromatic and euchromatic chromosome sets, which is usually maintained up to the cellularized endosperm. Pycnotic nuclei in the chalazal part of megagametophytes are characteristic of several embryo sec types, but only for Gagea spp. it is documented that such nuclei can take part in fertilization and endosperm formation. [References: 40]
机译：兼性异染色质不仅发生在与性别决定有关的某些动物中，而且还发生在至少一种植物属Gagea（Liliaceae s。str。）的成员中，而且在胚囊发育，受精和胚乳形成过程中发生。本文稿旨在为以前发生的事件提供无可争议的摄影和细胞计数证据，在此过程中，Gagea lutea的五倍体胚乳核中的三个完整基因组被异染色质化。在这种植物中，胚囊的形成通常遵循贝母类型即，胚囊是四孔的，并且孢子核的“ 1 + 3位置”之后是有丝分裂，其中三个查拉兹纺锤体融合并且形成两个三倍体核。三倍体蚕豆极核来自其中之一，这有助于五倍体胚乳。与小孔的珠子相比，这些位于胚囊查拉尔部分的细胞核显示出更强的凝聚力。在胚乳增殖过程中，三倍体极核的脓性得以维持甚至增强，而极小柱状极核和精子核则保持其常色状态。从第一个胚乳有丝分裂和随后的中间相中的异色染色体分布可以清楚地看出，来自中央细胞的三个棘形基因组的胚乳核中的异色团块的起源。 DNA含量的测量证实了异色和常色染色体组之间的3：2关系，该关系通常一直维持到细胞化的胚乳。大型配子体的睑板部分的比丘脑核是几种胚胎秒类型的特征，但仅对于盖格氏菌。据记载，这种核可以参与受精和胚乳形成。 [参考：40]

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