The internal transcribed spacer (1TS) region (1TS1, ITS2 and 5.8S rDNA) of the nuclear ribosomal DNA (nrDNA) was amplified via PCR in 28 taxa of Abies Mill. The amplified fragments showed length polymorphism among species, with species from Central America and two species from North America having a length of approximately 2 500 base pairs (bp) and the remaining taxa having a length of approximately 1 700 bp based on 100 bp and 1 kb ladder standard markers. The complete sequencing of ITS of Abies bracteata showed that the shorter type is 1 697 bp (1TS1 is 1 296 bp, 5.8S + 1TS2 is 401 bp). For the longer one, the partial rrs1 and complete 5.8S + ITS2 sequencing revealed that thelength of 5.8S + ITS2 is the same as that of the shorter type. The length difference of ITS in Abies is mainly due to the length difference in the ITS1 region, a result similar to the previous findings in other genera of Pinaceae. Variation in ITS length seems well correlated with morphological and geographic characters in Abies, suggesting that the length variation may be a phylogenetically informative character within the genus, long ITS was also found in other genera of Pinaceae in the previous studies. The long length of ITS in the family makes the sequencing of the region and subsequent alignment of sequences among species or genera more difficult than in taxa with short ITS, such as angiosperms. Although the length variation of ITS in the genus Abies is significant, the homogenous of ITS sequence between the longer one and the shorter one is obvious if the insertion in the longer ITS is ignored.
ITS（nrDNA）片段在冷杉属植物中的长度多态性及其在松科的系统与演化研究中的应用
向巧萍1* 向秋云2 Aaron LISTON3 傅立国1 傅德志1
（1. 中国科学院植物研究所，北京100093; 2.Department of Biological Sciences, Idaho State Unixersity, Pocatello, Idaho 83209-8007, USA;3. Department of Botany and Plant Pathology, Oregon State Unixersity,Corvallis, Corvallis, Oregon 97331-2902, USA)
摘要：由PCR反应扩增了 2 8种冷杉属 (Abies Mill.)植物的nrDNA的ITS(包括ITS1、ITS2和 5.8SrDNA)片段 ,经过与 1 0 0bp和 1kb的标准分子量DNA进行比较和某些类群ITS的全序列和部分序列测定 ,发现分布于墨西哥和 2种分布于北美的冷杉属植物的ITS片段长度约为 2 50 0bp ,而分布于欧亚大陆和其他分布于北美的冷杉植物的ITS长度约为 1 70 0bp ,二者相差约 80 0bp。A .bracteata (D .DonNutt.)的ITS全序列长度为 1 697bp ,其中ITS1为 1 2 96bp ,5.8S +ITS2为 4 0 1bp。A .durangensis的部分ITS1和全部 5.8S +ITS2的测序结果表明 ,5.8S +ITS2的长度与A .bracteata的相同 ,为 4 0 1bp ,从而揭示出ITS长度的变化主要是由于ITS1的长度变异所致。这与松科属间ITS长度的变异是由于ITS1长度的变异所致相一致。冷杉属ITS长度的变异式样与形态特征和地理分布具有很好的相关性。结合形态学性状和地理分布资料 ,初步探讨了ITS长度变异这一性状在冷杉植物系统演化中的意义 ,并对运用ITS片段探讨松科属间和属下的系统演化关系的可行性和局限性进行了讨论。认为较长的ITS片段应该为分析系统演化关系提供较大的信息量 ,可望得到具较高分辨率的结果 ,但松科植物属间较大的ITS片段的长度增大和长度变异不仅增加了基因扩增和测序的难
关键词： nrDNA ITS长度变异；系统演化；冷杉属；松科
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