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Science:异染色质是造成杂交不育主因

来源:生命经纬 2009-11-04 08:05

异染色质(核内深染部分)和常染色质(核内浅染部分)

生物物种往往是以生殖隔离来界定的。但自达尔文开始,生物学家就无法解释两个不同的物种杂交能够产生不育后代(如驴子和马杂交产生骡子)原因。最近,Fred Hutchinson癌症研究中心的一项新研究表明,上述原因可能与异染色质(heterochromatin)有关。这篇研究报告发表于10月22日的Science杂志上。

Joshua Bayes等人对果蝇(Drosophila)的一个特殊的基因——Odysseus进行研究,若将该基因导入到其他物种基因组中,导致雄性不育(male sterility)。Odysseus是一种转录因子基因,该基因所表达的蛋白质一直被认为能够开启果蝇睾丸(Drosophila testis)内其它基因的表达。

之前有研究表明,Odysseus的DNA结合域进化速度极快,因此课题组猜测Odysseus这种杂交不育蛋白或许能够结合到异染色质中重复的卫星DNA上。经过试验,研究人员发现结果与之前的假设一致——Bayes发现Odysseus蛋白能够结合到异染色质着丝粒附近或基因少的染色体(gene-poor chromosomes)的DNA上,并导致异染色质这些区域去凝缩(decondensation)。将Odysseus蛋白导入到别的物种中,能够与该物种Y染色体发生结合,并对精子形成的过程产生严重有害的影响。(生物谷Bioon.com)

相关研究:

Nature:染色质开放性与干细胞分化有关

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Science:揭示骡子为什么不能繁殖

生物谷推荐原始出处:

Science October 22, 2009 DOI: 10.1126/science.1181756

Altered Heterochromatin Binding by a Hybrid Sterility Protein in Drosophila Sibling Species

Joshua J. Bayes 1 and Harmit S. Malik 2*

1 Molecular and Cellular Biology Program, University of Washington, Seattle, WA 98185, USA.; Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.; Present address: Dernburg Lab, MCB, University of California Berkeley, Berkeley, CA 94720, USA.
2 HHMI, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.; Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.

Hybrid sterility of the heterogametic sex is one of the first postzygotic reproductive barriers to evolve during speciation, yet the molecular basis of hybrid sterility is poorly understood. We show that the hybrid male sterility gene Odysseus-site homeobox gene (OdsH) encodes a protein that localizes to evolutionarily dynamic loci within heterochromatin and leads to their decondensation. In D. mauritiana X D. simulans F1 male hybrids, OdsH from D. mauritiana (OdsHmau) acts as a sterilizing factor by associating with the heterochromatic Y chromosome of D. simulans, whereas D. simulans OdsH (OdsHsim) does not. Characterization of sterile hybrid testes revealed that OdsH expression and localization in the pre-meiotic phases of spermatogenesis differs between species. These results reveal that rapid heterochromatin evolution affects the onset of hybrid sterility.

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