Gametophytic selection in Arabidopsis thaliana supports the selective model of intron length reduction.
Gametophytic selection in Arabidopsis thaliana supports the selective model of intron length reduction.
复制标题
DOI：
10.1371/journal.pgen.0010013
复制
发表时间：
2005-08
期刊：
影响因子：
4.5
通讯作者：
Hurst LD
中科院分区：
文献类型：
--
作者：
Seoighe C;Gehring C;Hurst LD
为什么高表达基因有小内含子？这是一个重要的问题，尤其是因为它为比较基因组进化的选择主义和中立主义模型提供了一个试验场。有些人认为，小内含子是有选择地有利于降低转录成本。或者，大的内含子可能允许复杂的调控，而不需要高度表达的基因。这种“基因组设计”假说唤起了一个区域化的表达控制模型，因此可以解释为什么内含子大小与基因间距离协变，这一特征也与高表达基因聚集在具有高缺失率的基因组区域的假说一致。由于一些基因在单倍体阶段表达，因此受到特别强的纯化选择，拟南芥中基因的进化提供了一个新的试验场来区分这些可能性。重要的是，控制表达水平，在花粉中表达的基因比在孢子体中表达的基因具有更短的内含子。花粉表达基因两侧的基因具有平均大小的内含子和基因间距离，这与区域突变偏差和基因组设计相矛盾。因此，这些观察结果支持这样的观点，即选择效率有助于减少内含子长度，并提供了强配子体选择的分子特征的第一份报告。基因是奇怪的东西。小蛋白质通常由大基因编码。在这个过程中，许多多余的材料必须被剪下来扔掉。被丢弃的部分（内含子）的大小在基因之间差异很大。为什么会这样呢？作者利用植物基因在花粉中表达这一不寻常的事实，测试了三种不同的想法。由于花粉中的每个基因只有一个拷贝，自然选择的效果会更好一些。作者发现，在花粉中特别活跃的基因的非编码部分特别小。他们还发现，在花粉中活跃往往会使内含子变小。这有力地支持了这样一种观点，即小内含子是选择的结果，以减少制造太多只会被扔掉的材料的成本。
Why do highly expressed genes have small introns? This is an important issue, not least because it provides a testing ground to compare selectionist and neutralist models of genome evolution. Some argue that small introns are selectively favoured to reduce the costs of transcription. Alternatively, large introns might permit complex regulation, not needed for highly expressed genes. This “genome design” hypothesis evokes a regionalized model of control of expression and hence can explain why intron size covaries with intergene distance, a feature also consistent with the hypothesis that highly expressed genes cluster in genomic regions with high deletion rates. As some genes are expressed in the haploid stage and hence subject to especially strong purifying selection, the evolution of genes in Arabidopsis provides a novel testing ground to discriminate between these possibilities. Importantly, controlling for expression level, genes that are expressed in pollen have shorter introns than genes that are expressed in the sporophyte. That genes flanking pollen-expressed genes have average-sized introns and intergene distances argues against regional mutational biases and genomic design. These observations thus support the view that selection for efficiency contributes to the reduction in intron length and provide the first report of a molecular signature of strong gametophytic selection. Genes are odd things. Small proteins are often encoded by big genes. In the process, much of the excess material has to be cut out and thrown away. The size of the parts that are discarded (introns) differs greatly between genes. Why should this be so? The authors test three different ideas, making use of the unusual fact that in plants genes are expressed in pollen. As pollen has only one copy of every gene, natural selection is expected to work somewhat better. The authors find that the non-coding parts of genes that are especially active in pollen are particularly small. They also find that being active in pollen tends to make introns small. This provides strong support for the idea that small introns are the result of selection to reduce costs of making too much material that is only going to be thrown away.
登录
查看更多内容
影响因子：
3.5
作者：
Ophir, R;Graur, D
通讯作者：
Graur, D
影响因子：
10.5
作者：
IZBAN, MG;LUSE, DS
通讯作者：
LUSE, DS
影响因子：
7
作者：
Majewski, J;Ott, J
通讯作者：
Ott, J
影响因子：
56.9
作者：
Femino, A;Fay, FS;Singer, RH
通讯作者：
Singer, RH
影响因子：
3.3
作者：
Comeron, JM
通讯作者：
Comeron, JM