Freeling Lab, Plant and Microbial Biology, University of California - Berkeley Berkeley, CA, USA.
Front Plant Sci. 2012 May 15;3:94. doi: 10.3389/fpls.2012.00094. eCollection 2012.
The well supported gene dosage hypothesis predicts that genes encoding proteins engaged in dose-sensitive interactions cannot be reduced back to single copies once all interacting partners are simultaneously duplicated in a whole genome duplication. The genomes of extant flowering plants are the result of many sequential rounds of whole genome duplication, yet the fraction of genomes devoted to encoding complex molecular machines does not increase as fast as expected through multiple rounds of whole genome duplications. Using parallel interspecies genomic comparisons in the grasses and crucifers, we demonstrate that genes retained as duplicates following a whole genome duplication have only a 50% chance of being retained as duplicates in a second whole genome duplication. Genes which fractionated to a single copy following a second whole genome duplication tend to be the member of a gene pair with less complex promoters, lower levels of expression, and to be under lower levels of purifying selection. We suggest the copy with lower levels of expression and less purifying selection contributes less to effective gene-product dosage and therefore is under less dosage constraint in future whole genome duplications, providing an explanation for why flowering plant genomes are not overrun with subunits of large dose-sensitive protein complexes.
该基因剂量假说认为，在全基因组复制过程中，所有相互作用的伴侣同时被复制，那么编码参与剂量敏感相互作用的蛋白质的基因就不能减少到单拷贝。现存开花植物的基因组是多次全基因组复制的结果，但编码复杂分子机器的基因组部分并没有像多次全基因组复制所预期的那样快速增加。通过在禾本科和十字花科植物中进行平行的种间基因组比较，我们证明，在全基因组复制后保留为重复基因的基因，在第二次全基因组复制中只有 50%的机会保留为重复基因。在第二次全基因组复制后分离为单拷贝的基因往往是具有较少复杂启动子、较低表达水平和较低纯化选择水平的基因对的成员。我们认为，表达水平较低和纯化选择压力较小的拷贝对有效基因产物剂量的贡献较小，因此在未来的全基因组复制中受到的剂量限制较小，这解释了为什么开花植物基因组不会被大量的大剂量敏感蛋白质复合物亚基所占据。
