Jang C S, Kamps T L, Tang H, Bowers J E, Lemke C, Paterson A H
Plant Genome Mapping Laboratory, University of Georgia, Athens, GA 30602, USA.
Heredity (Edinb). 2009 Mar;102(3):266-73. doi: 10.1038/hdy.2008.119. Epub 2008 Nov 12.
What is the fate of organ-specific genes after the organ is lost? For Sorghum propinquum and Sorghum halepense genes that were previously shown to have rhizome-enriched expression, we have conducted comparative analysis of both coding regions and regulatory sequences in Sorghum bicolor (non-rhizomatousness) and S. propinquum (rhizomatousness). Most genes with rhizome-enriched expression appear to have similar numbers of paralogous copies in both genotypes, with only three of 24 genes studied showing significant differences in copy numbers. We detected no greater propensity for mutation in S. bicolor than in S. propinquum of genes with rhizome-enriched expression in the latter. Several cis-acting regulatory elements, particularly an Myb-binding core (AACGG) that is involved in the regulation of the mitotic cyclin, were more abundant in promoters of S. propinquum than in non-rhizomatous S. bicolor or Oryza sativa (rice). We suggest that many genes with rhizome-enriched expression in S. propinquum may serve multiple functions, with partial loss of some of these functions in S. bicolor but ongoing purifying selection acting to preserve the remaining functions. Expressed genes in polyploid S. halepense rhizomes appeared to be more frequently derived from the S. propinquum than the S. bicolor progenitor, but there was some evidence of formation of novel alleles and 'recruitment' of S. bicolor genes to rhizome-enriched expression in S. halepense, suggesting that polyploidy may have offered new evolutionary potential to S. halepense.
器官丢失后，器官特异性基因的命运如何？对于之前显示具有根状茎富集表达的拟高粱和石茅高粱基因，我们对双色高粱（非根状茎）和拟高粱（根状茎）的编码区和调控序列进行了比较分析。大多数具有根状茎富集表达的基因在两种基因型中似乎具有相似数量的旁系同源拷贝，在所研究的24个基因中只有3个显示出拷贝数的显著差异。我们没有检测到双色高粱中具有根状茎富集表达的基因的突变倾向比拟高粱中的更大。几个顺式作用调控元件，特别是参与有丝分裂细胞周期蛋白调控的Myb结合核心（AACGG），在拟高粱的启动子中比在非根状茎的双色高粱或水稻中更丰富。我们认为，拟高粱中许多具有根状茎富集表达的基因可能具有多种功能，在双色高粱中这些功能部分丧失，但持续的纯化选择作用于保留其余功能。多倍体石茅高粱根状茎中的表达基因似乎更频繁地来源于拟高粱而非双色高粱祖先，但有一些证据表明在石茅高粱中形成了新的等位基因以及将双色高粱基因“招募”到根状茎富集表达中，这表明多倍体可能为石茅高粱提供了新的进化潜力。
