Chimeric protein complexes in hybrid species generate novel phenotypes.
Chimeric protein complexes in hybrid species generate novel phenotypes.
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DOI：
10.1371/journal.pgen.1003836
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发表时间：
2013
期刊：
影响因子：
4.5
通讯作者：
Delneri D
中科院分区：
文献类型：
--
作者：
Piatkowska EM;Naseeb S;Knight D;Delneri D
物种间的杂交是新谱系起源和适应新环境的重要机制。增加的等位基因变异和转录网络的修饰是目前公认的两种力量，被认为是杂种中所见表型特性的原因。然而，由于细胞中的大多数生物功能是由蛋白质复合物完成的，因此种间蛋白质组装体代表了进化力量可以作用的自然变异的另一个重要来源。在这里，我们研究了两种不同的“严格意义上的”酵母杂交种中六种蛋白质复合物的组成，以了解尽管存在物种特异性的共同进化力，嵌合相互作用是否可以在细胞中自由形成，以及不同类型的复合物是否会导致杂交适应度的变化。通过亲和色谱法从杂交体中分离蛋白组装体，并通过质谱法鉴定。我们发现了四个测试的六个蛋白质组件的自发嵌合性的证据，我们表明，不同类型的复合物可以在选定的环境中引起各种表型。在TRP 2/TRP 3复合物的情况下，这种嵌合形成的效果导致杂交体在缺乏色氨酸的环境中的适应性优势，而只有一种类型的MBF复合物的亲本组合允许杂交体在呼吸条件下生长。这些表型依赖于遗传和环境背景。这项研究提供了经验证据，嵌合蛋白质复合物可以在细胞中自由组装，并揭示了一种新的机制，以产生表型新奇和可塑性的杂交，以补充基因复制所产生的基因组创新。在基因丢失的模式方面，交换直系亲属成员的能力对杂交后代的适应和随后的基因组进化也有重要意义。严格意义上的酿酒酵母（Saccharomycescerevisiae）是一个很好的例子，它是一个可以很容易地杂交以占据新生态位的密切相关的物种。杂交种携带双亲的DNA，可以显示不同的基因表达模式。关于杂交体中发生的蛋白质相互作用知之甚少，其中两个分歧的蛋白质组共存并负责正确执行生物功能。事实上，通过使用所有可用的亲本等位基因的不同组合，杂交体可以潜在地形成相同蛋白质复合物的不同嵌合变体。嵌合相互作用预计是次优的，因此不鼓励，因为形成蛋白质复合物的成员来自不同的亲本，并且具有不同的进化历史。有趣的是，在这里，我们通过实验表明，嵌合蛋白组装体自发地建立在不同的酵母杂交种中，并且这种嵌合性产生不同的表型变体，根据它们的遗传背景和它们所暴露的环境，这些表型变体显示出适应性的丧失或获得。这些研究结果意味着嵌合复合物的形成提供了一个新的自然变异来源，扩大了对新的营养环境的杂交种的适应潜力，并可能通过选择性保留最佳等位基因来影响基因组进化。
Hybridization between species is an important mechanism for the origin of novel lineages and adaptation to new environments. Increased allelic variation and modification of the transcriptional network are the two recognized forces currently deemed to be responsible for the phenotypic properties seen in hybrids. However, since the majority of the biological functions in a cell are carried out by protein complexes, inter-specific protein assemblies therefore represent another important source of natural variation upon which evolutionary forces can act. Here we studied the composition of six protein complexes in two different Saccharomyces “sensu stricto” hybrids, to understand whether chimeric interactions can be freely formed in the cell in spite of species-specific co-evolutionary forces, and whether the different types of complexes cause a change in hybrid fitness. The protein assemblies were isolated from the hybrids via affinity chromatography and identified via mass spectrometry. We found evidence of spontaneous chimericity for four of the six protein assemblies tested and we showed that different types of complexes can cause a variety of phenotypes in selected environments. In the case of TRP2/TRP3 complex, the effect of such chimeric formation resulted in the fitness advantage of the hybrid in an environment lacking tryptophan, while only one type of parental combination of the MBF complex allowed the hybrid to grow under respiratory conditions. These phenotypes were dependent on both genetic and environmental backgrounds. This study provides empirical evidence that chimeric protein complexes can freely assemble in cells and reveals a new mechanism to generate phenotypic novelty and plasticity in hybrids to complement the genomic innovation resulting from gene duplication. The ability to exchange orthologous members has also important implications for the adaptation and subsequent genome evolution of the hybrids in terms of pattern of gene loss. The Saccharomyces cerevisiae “sensu stricto” group represent an excellent example of closely related species which can readily hybridise to occupy new ecological niches. Hybrids harbour the DNA of both parents and can display diverse pattern of gene expression. Less is known about the protein interactions that occur in hybrids, where two diverged proteome co-exist and are responsible for the correct execution of the biological function. In fact, hybrids could potentially form different chimeric variants of the same protein complex by using all the different combinations of parental alleles available. Chimeric interactions are expected to be sub-optimal and therefore discouraged since the members forming the protein complex are from different parents and have a different evolutionary history. Interestingly, here, we show experimentally that chimeric protein assemblies are spontaneously established in different yeast hybrids, and that such chimericity produces different phenotypic variants displaying loss or gain of fitness according to their genetic background and to the environment that they are exposed. These findings imply that the formation of chimeric complexes offers a new source of natural variation, widens the adaptation potential of the hybrids towards new nutritional contexts, and may influence genome evolution through selective retention of optimal alleles.
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