Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3DS, UK;
Am J Bot. 2004 Jul;91(7):1022-35. doi: 10.3732/ajb.91.7.1022.
Tragopogon mirus and T. miscellus (both 2n = 4x = 24) are recent allotetraploids derived from T. dubius × T. porrifolius and T. dubius × T. pratensis (each 2n = 2x = 12), respectively. The genome sizes of T. mirus are additive of those of its diploid parents, but at least some populations of T. miscellus have undergone genome downsizing. To survey for genomic rearrangements in the allopolyploids, four repetitive sequences were physically mapped. TPRMBO (unit size 160 base pairs [bp]) and TGP7 (532 bp) are tandemly organized satellite sequences isolated from T. pratensis and T. porrifolius, respectively. Fluorescent in situ hybridization to the diploids showed that TPRMBO is a predominantly centromeric repeat on all 12 chromosomes, while TGP7 is a subtelomeric sequence on most chromosome arms. The distribution of tandem repetitive DNA loci (TPRMBO, TGP7, 18S-5.8S-26S rDNA, and 5S rDNA) gave unique molecular karyotypes for the three diploid species, permitting the identification of the parental chromosomes in the polyploids. The location and number of these loci were inherited without apparent changes in the allotetraploids. There was no evidence for major genomic rearrangements in Tragopogon allopolyploids that have arisen multiple times in North America within the last 80 yr.
美味蒲公英（2n = 4x = 24）和杂配蒲公英（2n = 4x = 24）都是由二倍体蒲公英×蒲公英（2n = 2x = 12）和二倍体蒲公英×天蓝蒲公英（2n = 2x = 12）杂交后加倍形成的异源四倍体。美味蒲公英的基因组大小是其双亲的累加，而至少有一些杂配蒲公英种群发生了基因组的缩小。为了检测异源多倍体中的基因组重排，我们对 4 个重复序列进行了物理作图。TPRMBO（单位大小为 160 个碱基对[bp]）和 TGP7（532 bp）是分别从天蓝蒲公英和蒲公英中分离出来的串联卫星序列。在二倍体上的荧光原位杂交表明，TPRMBO 是所有 12 条染色体上的主要着丝粒重复序列，而 TGP7 是大多数染色体臂上的端粒序列。串联重复 DNA 位点（TPRMBO、TGP7、18S-5.8S-26S rDNA 和 5S rDNA）的分布为三个二倍体物种提供了独特的分子核型，允许在多倍体中鉴定出亲代染色体。这些位点的位置和数量在异源四倍体中没有明显变化地被继承下来。在过去 80 年中，北美多次出现的蒲公英异源多倍体中，没有明显的基因组重排证据。
