FISH and gene analysis on the origin of high basic chromosome numbers of pteridophytes

用荧光原位杂交（FISH）方法分析了蕨类植物高碱基染色体数目的来源。本文报道了薇菜、薇菜、薇菜和薇菜属三种植物的染色体数目。茅ex Murray，和O.banksiifolia（Pr.）Kuhn，2n=44，核型相似。FISH结果显示，在日本稻和日本稻的中期板内有8个18S核糖体DNA（rDNA）位点。而在班克西叶野生稻中，检测到两个位点。为了获得其他二倍体物种，我们测定了鳞毛蕨属（鳞毛蕨科）的23个分类群，（鳞毛蕨科）的44个分类群，和双盖蕨属（Woodsiaceae）的54个分类群的体细胞染色体数目。在121个分类群中，有12个鳞毛蕨属、27个复叶耳蕨属和13个双盖蕨属为二倍体。FISH结果显示，二倍体双盖蕨（Diplaziumwichurae（Mett.）Diels，山毛蕨Di.amamianum Tagawa，掌叶鳞毛蕨Dryopteris handeliama C.Chr.，和孢子复叶耳蕨（Arachniodes sporadosora（Kunze）Nakaike）。这一证据表明，18SrDNA的重复是蕨类植物的一种近型特征，存在的同孢蕨类植物应该起源于高染色体数目。

The origin of high basic chromosome numbers of pteridophytes was analysed by a fluorescence in situ hybridization (FISH) method. The chromosome number of three species of Osmunda, O.japonica Thunb., O.lancea Thunb. ex Murray, and O.banksiifolia (Pr.) Kuhn, was 2n=44, and their karyotypes were very similar to each other. FISH revealed eight 18 S ribosomal DNA (rDNA) loci within a metaphase plate of O.japonica and O.lances. In O.banksiifolia, however, two loci were detected. To obtain other diploid species, we determined somatic chromosome numbers of 23 taxa of Dryopteris (Dryopteridaceae), 44 taxa of (Dryopteridaceae), and 54 taxa of Diplazium (Woodsiaceae). Out of 121 taxa examined, 12 of Dryopteris, 27 of Arachniodes, and 13 of Diplazium were diploids. FISH revealed six to eight 18 S rDNA loci within each metaphase plate of diploid species of Diplazium wichurae (Mett.) Diels, Di.amamianum Tagawa, Dryopteris handeliama C.Chr., and Arachniodes sporadosora (Kunze) Nakaike. This evidence suggested that the duplication of 18 S rDNA should be a plesiomorphic character in pteridophytes and exist homosporous ferns should be originated with high chromosome numbers.