Santini S, Cavallini A, Natali L, Minelli S, Maggini F, Cionini P G
Dipartimento di Biologia delle Piante Agrarie della Università, Sezione di Genetica, via G Matteotti 1/B, 56124 Pisa, Italy.
Chromosoma. 2002 Sep;111(3):192-200. doi: 10.1007/s00412-002-0196-2. Epub 2002 Jun 27.
Two repeated DNA sequences isolated from a partial genomic DNA library of Helianthus annuus, p HaS13 and p HaS211, were shown to represent portions of the int gene of a Ty3 /gypsy retroelement and of the RNase-Hgene of a Ty1 /copia retroelement, respectively. Southern blotting patterns obtained by hybridizing the two probes to BglII- or DraI-digested genomic DNA from different Helianthus species showed p HaS13 and p HaS211 were parts of dispersed repeats at least 8 and 7 kb in length, respectively, that were conserved in all species studied. Comparable hybridization patterns were obtained in all species with p HaS13. By contrast, the patterns obtained by hybridizing p HaS211 clearly differentiated annual species from perennials. The frequencies of p HaS13- and p HaS211-related sequences in different species were 4.3x10(4)-1.3x10(5) copies and 9.9x10(2)-8.1x10(3) copies per picogram of DNA, respectively. The frequency of p HaS13-related sequences varied widely within annual species, while no significant difference was observed among perennial species. Conversely, the frequency variation of p HaS211-related sequences was as large within annual species as within perennials. Sequences of both families were found to be dispersed along the length of all chromosomes in all species studied. However, Ty3 /gypsy-like sequences were localized preferentially at the centromeric regions, whereas Ty1/ copia-like sequences were less represented or absent around the centromeres and plentiful at the chromosome ends. These findings suggest that the two sequence families played a role in Helianthusgenome evolution and species divergence, evolved independently in the same genomic backgrounds and in annual or perennial species, and acquired different possible functions in the host genomes.
从向日葵（Helianthus annuus）的部分基因组DNA文库中分离出的两个重复DNA序列，即p HaS13和p HaS211，分别被证明代表Ty3 /gypsy逆转录元件的int基因部分和Ty1 /copia逆转录元件的RNase-H基因部分。用这两种探针与来自不同向日葵物种的经BglII或DraI消化的基因组DNA杂交得到的Southern杂交图谱表明，p HaS13和p HaS211分别是长度至少为8 kb和7 kb的分散重复序列的一部分，这些重复序列在所有研究的物种中都是保守的。在所有物种中用p HaS13都获得了类似的杂交图谱。相比之下，用p HaS211杂交得到的图谱清楚地将一年生物种与多年生物种区分开来。不同物种中与p HaS13和p HaS211相关序列的频率分别为每皮克DNA 4.3×10⁴ - 1.3×10⁵个拷贝和9.9×10² - 8.1×10³个拷贝。与p HaS13相关序列的频率在一年生物种中变化很大，而在多年生物种之间未观察到显著差异。相反，与p HaS211相关序列的频率在一年生物种和多年生物种中的变化一样大。在所研究的所有物种中，发现这两个家族的序列都沿着所有染色体的长度分散分布。然而，Ty3 /gypsy样序列优先定位在着丝粒区域，而Ty1 /copia样序列在着丝粒周围较少出现或不存在，在染色体末端则大量存在。这些发现表明，这两个序列家族在向日葵基因组进化和物种分化中发挥了作用，在相同的基因组背景以及一年生或多年生物种中独立进化，并在宿主基因组中获得了不同的可能功能。
