加拿大蒙特利爾大學(xué)研究人員在生物體如何選擇其交配伴侶的機(jī)理研究上取得重要進(jìn)展。他們發(fā)現(xiàn),，一種分子開關(guān)在對某個潛在的交配對象的信號做出反應(yīng)時,，分子開關(guān)得以激活。分子開關(guān)的激活使生物體知道附近有一個健康的最佳交配候選對象,，并做出交配決定,。相關(guān)文章發(fā)表在最新出版的《自然》雜志上,。
達(dá)爾文在150年前首次發(fā)現(xiàn)生物體如何選擇和為什么選擇的交配對象的行為原則。達(dá)爾文曾經(jīng)詳細(xì)解釋了一頭母獅為何會選擇一頭最強(qiáng)壯的雄獅進(jìn)行交配,，一只母孔雀為何會選擇一只羽毛最美麗的公孔雀交配的原因,。加拿大科學(xué)家使用酵母菌在分子水平上發(fā)現(xiàn)了與達(dá)爾文理論相同的交配對象選擇原理。
加拿大蒙特利爾大學(xué)生化系教授斯蒂芬·米奇尼克介紹說,，研究結(jié)果表明,，交配的決定由一種簡單的化學(xué)開關(guān)所控制，這種開關(guān)將收到的生物信息素信號轉(zhuǎn)換成了細(xì)胞的反應(yīng),。
他介紹,，當(dāng)生物信息素信號增強(qiáng)時，細(xì)胞中的兩個生化酶開始互相競爭,，其中一個得到加強(qiáng),，而另一個則會在代號為Ste5的蛋白質(zhì)上移除一個化學(xué)修飾。在生物信息素信號達(dá)到關(guān)鍵的閥值時,，生物酶中的一個經(jīng)過競爭,，其能力超過了另一個經(jīng)過生物酶修飾Ste5蛋白質(zhì)的能力，細(xì)胞就會收到一個即時的化學(xué)信息,，該信息即是：交配時間到了,。
研究中，科學(xué)家使用了一種單細(xì)胞生物體酵母菌作為對象,。米奇尼克教授認(rèn)為,，雖然酵母菌與人體存在很大的不同，但是在分子和細(xì)胞水平卻有許多相似之處,?？茖W(xué)家在酵母菌中所發(fā)現(xiàn)的可開關(guān)的分子，與在人體細(xì)胞內(nèi)發(fā)現(xiàn)的分子形式非常相似,。
研究人員表示,，使用酵母菌可以展示出細(xì)胞如何做出一個重要的決定。當(dāng)酵母細(xì)胞決定要交配時,，它們必須知道很靠近的地方存在一個交配對象,，然后迅速做出準(zhǔn)備交配的決定。研究發(fā)現(xiàn),，酵母細(xì)胞做出決定不僅快,，而且非常精確。盡管附近有許多處于競爭狀態(tài)的候選交配對象,，它們?nèi)匀豢梢宰龀鲎罴训倪x擇,。(生物谷Bioon.com)
Nature：酵母菌株基因圖譜助釀美酒
Cell：揭開酵母菌雜種不育奧秘
生物谷推薦原文出處：
Nature doi:10.1038/nature08946
The scaffold protein Ste5 directly controls a switch-like mating decision in yeast
Mohan K. Malleshaiah1,6, Vahid Shahrezaei3,6, Peter S. Swain4,5 & Stephen W. Michnick1,2
1 Département de Biochimie,
2 Centre Robert-Cedergren, Bio-Informatique et Génomique Université de Montréal, C.P. 6128, Succursale centre-ville Montréal, Québec H3C 3J7, Canada
3 Department of Mathematics, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
4 Department of Physiology, McGill University, 3655 Promenade Sir William Osler, Montréal, Québec H3G 1Y6, Canada
5 Centre for Systems Biology at Edinburgh, University of Edinburgh, Edinburgh EH9 3JD, UK
6 These authors contributed equally to this work.
Evolution has resulted in numerous innovations that allow organisms to increase their fitness by choosing particular mating partners, including secondary sexual characteristics, behavioural patterns, chemical attractants and corresponding sensory mechanisms1. The haploid yeast Saccharomyces cerevisiae selects mating partners by interpreting the concentration gradient of pheromone secreted by potential mates through a network of mitogen-activated protein kinase (MAPK) signalling proteins2, 3. The mating decision in yeast is an all-or-none, or switch-like, response that allows cells to filter weak pheromone signals, thus avoiding inappropriate commitment to mating by responding only at or above critical concentrations when a mate is sufficiently close4. The molecular mechanisms that govern the switch-like mating decision are poorly understood. Here we show that the switching mechanism arises from competition between the MAPK Fus3 and a phosphatase Ptc1 for control of the phosphorylation state of four sites on the scaffold protein Ste5. This competition results in a switch-like dissociation of Fus3 from Ste5 that is necessary to generate the switch-like mating response. Thus, the decision to mate is made at an early stage in the pheromone pathway and occurs rapidly, perhaps to prevent the loss of the potential mate to competitors. We argue that the architecture of the Fus3–Ste5–Ptc1 circuit generates a novel ultrasensitivity mechanism, which is robust to variations in the concentrations of these proteins. This robustness helps assure that mating can occur despite stochastic or genetic variation between individuals. The role of Ste5 as a direct modulator of a cell-fate decision expands the functional repertoire of scaffold proteins beyond providing specificity and efficiency of information processing5, 6. Similar mechanisms may govern cellular decisions in higher organisms and be disrupted in cancer.
