Vaio Magdalena, Speranza Pablo, Valls José Francisco, Guerra Marcelo, Mazzella Cristina
Laboratory of Genetics, Department of Plant Biology, Facultad de Agronomía, Universidad de la República, Av. E. Garzón 780 CP12900, Montevideo, Uruguay.
Ann Bot. 2005 Aug;96(2):191-200. doi: 10.1093/aob/mci168. Epub 2005 May 23.
The Quadrifaria group of Paspalum (Poaceae, Paniceae) comprises species native to the subtropical and temperate regions of South America. The purpose of this research was to characterize the I genomes in five species of this group and to establish phylogenetic relationships among them.
Prometaphase chromatin condensation patterns, the physical location of 5S and 45S rDNA sites by fluorescence in situ hybridization (FISH), and sequences of five chloroplast non-coding regions were analysed.
The condensation patterns observed were highly conserved among diploid and tetraploid accessions studied and not influenced by the dyes used or by the FISH procedure, allowing the identification of almost all the chromosome pairs that carried the rDNA signals. The FISH analysis of 5S rDNA sites showed the same localization and a correspondence between the number of sites and ploidy level. In contrast, the distribution of 45S rDNA sites was variable. Two general patterns were observed with respect to the location of the 45S rDNA. The species and cytotypes Paspalum haumanii 2x, P. intermedium 2x, P. quadrifarium 4x and P. exaltatum 4x showed proximal sites on chromosome 8 and two to four distal sites in other chromosomes, while P. quarinii 4x and P. quadrifarium 2x showed only distal sites located on a variable number of small chromosomes and on the long arm of chromosome 1. The single most-parsimonious tree found from the phylogenetic analysis showed the Quadrifaria species partitioned in two clades, one of them includes P. haumanii 2x and P. intermedium 2x together with P. quadrifarium 4x and P. exaltatum 4x, while the other contains P. quadrifarium 2x and P. quarinii 4x.
The subdivision found with FISH is consistent with the clades recovered with cpDNA data and both analyses suggest that the Quadrifaria group, as presently defined, is not monophyletic and its species belong in at least two clades.
雀稗属（禾本科，黍亚科）的Quadrifaria组包含原产于南美洲亚热带和温带地区的物种。本研究的目的是对该组五个物种的I基因组进行特征分析，并确定它们之间的系统发育关系。
分析了前中期染色质凝聚模式、通过荧光原位杂交（FISH）确定的5S和45S rDNA位点的物理位置，以及五个叶绿体非编码区的序列。
在所研究的二倍体和四倍体材料中观察到的凝聚模式高度保守，不受所用染料或FISH程序的影响，从而能够识别几乎所有携带rDNA信号的染色体对。5S rDNA位点的FISH分析显示出相同的定位以及位点数量与倍性水平之间的对应关系。相比之下，45S rDNA位点的分布是可变的。关于45S rDNA的位置观察到两种一般模式。物种和细胞型的雀稗2x、居间雀稗2x、四穗雀稗4x和高秆雀稗4x在染色体8上显示近端位点，在其他染色体上显示两到四个远端位点，而夸氏雀稗4x和四穗雀稗2x仅在可变数量的小染色体和染色体1的长臂上显示远端位点。系统发育分析中找到的单一最简约树显示Quadrifaria物种分为两个分支，其中一个分支包括雀稗2x和居间雀稗2x以及四穗雀稗4x和高秆雀稗4x，而另一个分支包含四穗雀稗2x和夸氏雀稗4x。
FISH发现的细分与cpDNA数据恢复的分支一致，并且两项分析均表明，目前定义的Quadrifaria组不是单系的，其物种至少属于两个分支。
