Unusual compact rDNA gene arrangements within some members of the Ascomycota: evidence for molecular co-evolution between ITS1 and ITS2
Unusual compact rDNA gene arrangements within some members of the Ascomycota: evidence for molecular co-evolution between ITS1 and ITS2
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作者：
Hausner, G;Wang, X
在子囊菌属Sphaeronaemella中检测了核糖体DNA串联重复序列的内部转录间隔区。Sphaeronaemella和其有丝分裂对应的Gabarnaudia物种，由于异常短的内部转录间隔区(ITS)，具有紧密的rDNA基因排列。对这些区域的研究表明，它们的ITS1和ITS2区域可以折叠成中心发夹状结构，而Sphaeronaemella种的尺寸减小是由于主发夹的长度缩短和主发夹发出的较小的发夹状结构的丢失。数据库汇编结合新获得的序列，提供了一个ITS数据集，其中包括属于子囊菌门的600个物种的序列。相关分析表明，ITS1和ITS2的大小呈显著正相关，表明这两个rDNA区域是共同进化的。这支持了生化证据，表明ITS1和ITS2片段相互作用，促进rRNA前体的成熟。
The internal transcribed spacers of the ribosomal DNA tandem repeat were examined in members of the ascomycetous genus Sphaeronaemella. Species of Sphaeronaemella and its mitotic counterpart Gabarnaudia, have a compact rDNA gene arrangement due to unusually short internal transcribed spacer (ITS) regions. Examination of these regions from phylogenetically related taxa, Cornuvesica, Gondwanamyces, and Ceratocystis, showed that their ITS1 and ITS2 regions could be folded into central hairpin-like structures with the size reduction in species of Sphaeronaemella being due to length reduction of the main-hairpin and the loss of smaller hairpin-like structures that emanate from the main hairpin. A databank compilation, combined with newly obtained sequences, provided an ITS data set that includes sequences of 600 species belonging to the Ascomycota. Correlation analysis revealed that the sizes of ITS1 and ITS2 show a strong positive correlation, suggesting that the 2 rDNA regions have co-evolved. This supports biochemical evidence indicating that the ITS1 and ITS2 segments interact to facilitate the maturation of the rRNA precursor.