Casanova-Sáez Rubén, Candela Héctor, Micol José Luis
Instituto de Bioingeniería, Universidad Miguel Hernández, Campus de Elche, 03202 Elche, Alicante, Spain.
Sci Rep. 2014 Feb 18;4:4122. doi: 10.1038/srep04122.
Whole-genome duplication events have driven to a large degree the evolution of angiosperm genomes. Although the majority of redundant gene copies after a genome duplication are lost, subfunctionalization or gene balance account for the retention of gene copies. The Arabidopsis 80S ribosome represents an excellent model to test the gene balance hypothesis as it consists of 80 ribosomal proteins, all of them encoded by genes belonging to small gene families. Here, we present the isolation of mutant alleles of the APICULATA2 (API2) and RPL36aA paralogous genes, which encode identical ribosomal proteins but share a similarity of 89% in their coding sequences. RPL36aA was found expressed at a higher level than API2 in the wild type. The loss-of-function api2 and rpl36aa mutations are recessive and affect leaf development in a similar way. Their double mutant combinations with asymmetric leaves2-1 (as2-1) caused leaf polarity defects that were stronger in rpl36aa as2-1 than in api2 as2-1. Our results highlight the role of combined haploinsufficiency and purifying selection in the retention of these paralogous genes in the Arabidopsis genome.
全基因组复制事件在很大程度上推动了被子植物基因组的进化。虽然基因组复制后大多数冗余基因拷贝会丢失，但亚功能化或基因平衡解释了基因拷贝得以保留的原因。拟南芥80S核糖体是检验基因平衡假说的一个极佳模型，因为它由80种核糖体蛋白组成，所有这些蛋白均由属于小基因家族的基因编码。在此，我们展示了对APICULATA2（API2）和RPL36aA旁系同源基因的突变等位基因的分离，这两个基因编码相同的核糖体蛋白，但它们的编码序列有89%的相似性。在野生型中，RPL36aA的表达水平高于API2。功能缺失型api2和rpl36aa突变是隐性的，且以相似的方式影响叶片发育。它们与不对称叶片2-1（as2-1）的双突变组合导致叶片极性缺陷，在rpl36aa as2-1中比在api2 as2-1中更严重。我们的结果突出了组合单倍剂量不足和纯化选择在拟南芥基因组中保留这些旁系同源基因方面的作用。
