Liu Zhenlan, Adams Keith L
UBC Botanical Garden and Centre for Plant Research and Department of Botany, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia V6T 1Z4, Canada.
Curr Biol. 2007 Oct 9;17(19):1669-74. doi: 10.1016/j.cub.2007.08.030. Epub 2007 Sep 6.
Allopolyploidy has been a prominent mode of speciation and a recurrent process during plant evolution and has contributed greatly to the large number of duplicated genes in plant genomes [1-4]. Polyploidy often leads to changes in genome organization and gene expression [5-9]. The expression of genes that are duplicated by polyploidy (termed homeologs) can be partitioned between the duplicates so that one copy is expressed and functions only in some organs and the other copy is expressed only in other organs, indicative of subfunctionalization [10]. To determine how homeologous-gene expression patterns change during organ development and in response to abiotic stress conditions, we have examined expression of the alcohol dehydrogenase gene AdhA in allopolyploid cotton (Gossypium hirsutum). Expression ratios of the two homeologs vary considerably during the development of organs from seedlings and fruits. Abiotic stress treatments, including cold, dark, and water submersion, altered homeologous-gene expression. Most notably, only one copy is expressed in hypocotyls during a water-submersion treatment, and only the other copy is expressed during cold stress. These results imply that subfunctionalization of genes duplicated by polyploidy has occurred in response to abiotic stress conditions. Partitioning of duplicate gene expression in response to environmental stress may lead to duplicate gene retention during subsequent evolution.
异源多倍体一直是植物进化过程中物种形成的主要模式和反复出现的过程，并且对植物基因组中大量的重复基因产生了巨大影响[1-4]。多倍体常常导致基因组组织和基因表达的变化[5-9]。由多倍体复制产生的基因（称为同源基因）的表达可以在这些复制品之间进行分配，使得一个拷贝仅在某些器官中表达并发挥功能，而另一个拷贝仅在其他器官中表达，这表明了亚功能化[10]。为了确定同源基因的表达模式在器官发育过程中以及对非生物胁迫条件的响应中如何变化，我们研究了异源多倍体棉花（陆地棉）中乙醇脱氢酶基因AdhA的表达。在幼苗和果实器官发育过程中，两个同源基因的表达比例差异很大。包括冷、暗和水浸在内的非生物胁迫处理改变了同源基因的表达。最值得注意的是，在水浸处理期间，下胚轴中仅表达一个拷贝，而在冷胁迫期间仅表达另一个拷贝。这些结果表明，由多倍体复制产生的基因的亚功能化是对非生物胁迫条件的响应。响应环境胁迫而对重复基因表达进行分配可能会导致重复基因在随后的进化过程中得以保留。
