Murray Brian G, Friesen Nikolai, Heslop-Harrison J S Pat
School of Biological Sciences, University of Auckland, New Zealand.
Ann Bot. 2002 Apr;89(4):483-9. doi: 10.1093/aob/mcf047.
DNA sequences have been mapped to the chromosomes of Podocarpus species from New Zealand and Australia by fluorescent in situ hybridization. Unlike other conifers, these species show only one pair of major sites of 45S rDNA genes, and two additional minor sites were seen in the Australian P. lawrencei. Unusually, 45S sequences collocalize to the same chromosomal region as the 5S rDNA. The telomere probe (TTTAGGG)n hybridizes to the ends of all chromosomes as well as to a large number of small sites distributed along the length of all chromosomes. Two other simple sequence repeats, (AAC)5 and (GATA)4, show a diffuse pattern of hybridization sites distributed along chromosomes. Southern blots using a variety of probes obtained from the reverse transcriptase of retroelements (gypsy, copia and LINE) from P. totara, P. nivalis and Dacrycarpus dacrydioides show that these retroelements are abundant and widespread in Podocarpaceae and also in others conifers. Some retroelements such as copia pPonty3 and gypsy pPot1li are more abundant in the genome of Picea abies and Ginkgo biloba than in the species from which they were amplified.
通过荧光原位杂交技术，已将DNA序列定位到来自新西兰和澳大利亚的罗汉松属物种的染色体上。与其他针叶树不同，这些物种仅显示一对主要的45S rDNA基因位点，并且在澳大利亚的劳伦斯罗汉松中还观察到另外两个次要位点。不同寻常的是，45S序列与5S rDNA位于同一染色体区域。端粒探针(TTTAGGG)n与所有染色体的末端以及沿所有染色体长度分布的大量小位点杂交。另外两个简单序列重复(AAC)5和(GATA)4显示出沿染色体分布的杂交位点的弥散模式。使用从罗汉松、雪山罗汉松和泪柏的逆转录元件(吉普赛、考皮亚和长散在重复序列)的逆转录酶获得的各种探针进行的Southern杂交表明，这些逆转录元件在罗汉松科以及其他针叶树中丰富且广泛存在。一些逆转录元件，如考皮亚pPonty3和吉普赛pPot1li，在欧洲云杉和银杏的基因组中比在扩增它们的物种中更为丰富。
