摘要
种子植物核rDNA是高度重复的串联序列,由于同步进化的力量,大多数物种中这些重复单位间已发生纯合或接近纯合。5.8S rDNA把核rDNA的内转录间隔区分为ITS1和ITS2两部分,在被子植物中ITS1的长度为165-298 bp,ITS2的长度为177-266 bp,而在裸子植物中ITS片段较长,且其长度变化主要由ITS1的长度变异所致。可对这两个片段PCR产物进行直接测序或克隆测序。由于ITS序列变异较快,能够提供较丰富的变异位点和信息位点,已成为被子植物较低分类阶元的系统发育和分类研究中的重要分子标记,为探讨多倍体复合体网状进化关系,异源多倍体的起源提供了重要的系统学信息,但它一般不适合科以上水平的系统学研究。裸子植物中ITS片段较长,重复序列间的纯合程度不同,测序比较困难,因此对探讨裸子植物系统发育和分类受到了一定的限制,但近年来有所发展。
Nuclear rDNA in seed plants is a tandem sequence of highly-repeatable units that have become homogenized or nearly so in most species. 5. 8S rDNA makes the internal transcribed spacers of nuclear rDNA divide into ITS1 and ITS2. In angiosperms, ITS1 and ITS2 ranges between 165 bp and 298 bp, and 177 bp and 266 bp, respectively; the ITS is relatively long in gymnosperms because its length depends on ITS1 length. Direct sequencing and cloned sequencing of the PCR products of the two fragments can be done. Because ITS sequences mutate quickly, they are capable of providing many variable sites and informative sites , which have become the important molecular markers in the systematic development and classification researches of low-order angiosperm categories , and providing important systematic information for exploring polyploid reticulate evolution and allopolyploid origins, but it is not suitable for family and above-family phylogenetic researches. Because ITS in gymnosperms is relatively long, its repeated sequences differently homogenize and its sequencing is relatively difficult, it is limited to study gymnosperm phylogenetic development and classification although some advances has been made in recent years.
出处
《西北植物学报》
CAS
CSCD
北大核心
2005年第4期829-834,共6页
Acta Botanica Boreali-Occidentalia Sinica
基金
国家自然科学基金资助项目30270927
