Udovicic F, McFadden G I, Ladiges P Y
School of Botany, University of Melbourne, Parkville, Victoria, Australia.
Mol Phylogenet Evol. 1995 Sep;4(3):247-56. doi: 10.1006/mpev.1995.1023.
Sequences of the 5S rDNA repeat have been determined from four outgroup taxa (Arillastrum group), 2 Angophora species, and 19 Eucalyptus species (including representatives from all informal subgenera). Alignment shows that, as in other plants, the tandemly repeated 5S rRNA genes are highly conserved while the noncoding intergenic spacers are variable. A 50-base pair (bp) repeating element, which has undergone duplication and modification in certain taxa, is identifiable within the spacer and accounts for much of the variability. There were several other multiresidue deletion/insertion events in the spacers that define major clades. Based on the indel events and modifications of the 50-bp element it is apparent that the spacer from bloodwood (informal subgenera Blakella and Corymbia) species of Eucalyptus is more similar to that of Angophora than to non-bloodwood species of Eucalyptus. Parsimony analysis showed Eucalyptus to be paraphyletic, with the bloodwoods being more closely related to Angophora than to the rest of Eucalyptus. This finding supports taxonomic revision of Eucalyptus.
已测定了来自四个外类群分类单元（Arillastrum组）、2种桃金娘科桉属植物和19种桉属植物（包括所有非正式亚属的代表）的5S核糖体DNA重复序列。比对结果表明，与其他植物一样，串联重复的5S核糖体RNA基因高度保守，而非编码基因间隔区则具有变异性。在间隔区内可识别出一个50个碱基对（bp）的重复元件，该元件在某些分类单元中经历了复制和修饰，是变异性的主要来源。间隔区内还有其他几个多残基缺失/插入事件，这些事件定义了主要分支。基于插入缺失事件和50-bp元件的修饰，很明显，桉属植物中红桉类（非正式亚属Blakella和伞房桉属）物种的间隔区与桃金娘科桉属植物的间隔区比与桉属非红桉类物种的间隔区更相似。简约分析表明桉属植物是并系的，红桉类与桃金娘科桉属植物的关系比与桉属其他植物的关系更密切。这一发现支持了桉属植物的分类修订。
