3月26日,，《PLoS Biology》以封面文章發(fā)表了題為“Selecting One of Several Mating Types through Gene Segment Joining and Deletion in Tetrahymena thermophila”的研究論文（http：//www.plosbiology.org/），該研究成果由中國(guó)科學(xué)院水生生物研究所原生動(dòng)物功能基因組學(xué)學(xué)科組繆煒研究員等人與美國(guó)加州大學(xué)圣巴巴拉分校Orias教授實(shí)驗(yàn)室合作完成,。
單細(xì)胞真核生物通常是通過無(wú)性生殖方式進(jìn)行繁殖的,，但其生活史中一般都存在有性生殖階段，以此來(lái)增加遺傳多樣性以適應(yīng)多變的環(huán)境,。1937年,，Sonneborn首先在草履蟲(Paramecium Aurelia)中發(fā)現(xiàn)了形態(tài)上無(wú)法區(qū)分但能夠通過自我/非自我(self/non-self)識(shí)別方式進(jìn)行有性生殖的交配型系統(tǒng)，隨后該系統(tǒng)被證實(shí)廣泛存在于從細(xì)菌到單細(xì)胞真核生物的各種微生物類群中,。
嗜熱四膜蟲(Tetrahymena thermophila)是一種優(yōu)良的單細(xì)胞真核模式生物。1953年,，Nanney教授首次對(duì)嗜熱四膜蟲交配型進(jìn)行了描述,，鑒定出具有7種不同的交配型，這為后來(lái)利用嗜熱四膜蟲的有性生殖建立成熟的基因操作技術(shù)并將其發(fā)展為模式生物奠定了重要基礎(chǔ),。1954至1960年間,，Orias作為Nanney教授的博士生開始了四膜蟲交配型的研究,。然而，半個(gè)多世紀(jì)過去了,，關(guān)于嗜熱四膜蟲交配型決定的分子基礎(chǔ)和機(jī)制問題一直懸而未決,，成為困擾四膜蟲研究領(lǐng)域的一大難題。2011年,，繆煒研究團(tuán)隊(duì)通過對(duì)不同交配型嗜熱四膜蟲在饑餓早期的轉(zhuǎn)錄組數(shù)據(jù)進(jìn)行比較分析,，精確預(yù)測(cè)出了嗜熱四膜蟲的交配型決定基因：一對(duì)“頭對(duì)頭”的基因?qū)Γ╝ pair of genes arranged head-to-head）。之后通過和Orias教授的深入合作,，最終揭示了嗜熱四膜蟲交配型決定的分子機(jī)制：包括所有交配型決定基因?qū)卧氖葻崴哪はx小核,，在有性生殖過程中，經(jīng)過一系列的程序化DNA重排（programed DNA rearrangements）發(fā)育成只含有一個(gè)交配型決定基因?qū)卧拇蠛恕?/p>
該研究成果,，不僅揭示了纖毛類原生動(dòng)物交配型決定的機(jī)制,，還對(duì)于性別決定和起源進(jìn)化、細(xì)胞自我/非自我識(shí)別,、腫瘤/癌癥發(fā)生相關(guān)的DNA重排機(jī)制的認(rèn)識(shí)具有重要價(jià)值,。（生物谷Bioon.com）
doi:10.1371/journal.pbio.1001518
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Selecting One of Several Mating Types through Gene Segment Joining and Deletion in Tetrahymena thermophila
Cervantes MD, Hamilton EP, Xiong J, Lawson MJ, Yuan D, et al
The unicellular eukaryote Tetrahymena thermophila has seven mating types. Cells can mate only when they recognize cells of a different mating type as non-self. As a ciliate, Tetrahymena separates its germline and soma into two nuclei. During growth the somatic nucleus is responsible for all gene transcription while the germline nucleus remains silent. During mating, a new somatic nucleus is differentiated from a germline nucleus and mating type is decided by a stochastic process. We report here that the somatic mating type locus contains a pair of genes arranged head-to-head. Each gene encodes a mating type-specific segment and a transmembrane domain that is shared by all mating types. Somatic gene knockouts showed both genes are required for efficient non-self recognition and successful mating, as assessed by pair formation and progeny production. The germline mating type locus consists of a tandem array of incomplete gene pairs representing each potential mating type. During mating, a complete new gene pair is assembled at the somatic mating type locus; the incomplete genes of one gene pair are completed by joining to gene segments at each end of germline array. All other germline gene pairs are deleted in the process. These programmed DNA rearrangements make this a fascinating system of mating type determination.d promote diet niche partitioning of predators and thus elevates the strength of top-down control.
