流式细胞术和 GISH 揭示了混合倍性群体和具 S. alterniflora 和 S. maritima 基因组的 Spartina 非整倍体。
Flow cytometry and GISH reveal mixed ploidy populations and Spartina nonaploids with genomes of S. alterniflora and S. maritima origin.
机构信息
Queen Mary University of London, School of Biological and Chemical Sciences, London E1 4NS, UK.
出版信息
Ann Bot. 2010 Apr;105(4):527-33. doi: 10.1093/aob/mcq008. Epub 2010 Feb 11.
BACKGROUND
The genus Spartina exhibits extensive hybridization and includes classic examples of recent speciation by allopolyploidy. In the UK there are two hexaploid species, S. maritima and S. alterniflora, as well as the homoploid hybrid S. x townsendii (2n = 60) and a derived allododecaploid S. anglica (2n = 120, 122, 124); the latter two are considered to have originated in Hythe, southern England at the end of the 19th century.
METHODS
Genomic in situ hybridization (GISH) and flow cytometry were used to characterize the genomic composition and distribution of these species and their ploidy levels at Eling Marchwood and Hythe, both near Southampton, southern England.
KEY RESULTS
GISH identified approx. 60 chromosomes each of S. maritima and S. alterniflora origin in S. anglica and 62 chromosomes from S. alterniflora and 30 chromosomes from S. maritima in a nonaploid individual from Eling Marchwood, UK. GISH and flow cytometry also revealed that most (94 %) individuals examined at Hythe were hexaploid (the remaining two individuals (6 %) were dodedcaploid; n = 34), whereas hexaploid (approx. 36 % of plants), nonaploid (approx. 27 %) and dodecaploid (approx. 36 %) individuals were found at Eling Marchwood (n = 22).
CONCLUSIONS
Nonaploid individuals indicate the potential for introgression between hexaploid and dodecaploid species, complicating the picture of polyploid-induced speciation within the genus. Despite the aggressive ecological habit of S. anglica, it has not out-competed S. x townsendii at Hythe (homoploid hybrids at a frequency of 94 %, n = 34), despite >100 years of coexistence. The success of GISH opens up the potential for future studies of polyploid-induced genome restructuring in this genus.
背景
米草属表现出广泛的杂交现象，包括由异源多倍体形成的典型新物种形成实例。在英国，有两个六倍体物种，米草和互花米草，以及同源的杂种米草（2n=60）和一个衍生的十二倍体米草（2n=120、122、124）；后两者被认为起源于 19 世纪末英格兰南部的海斯。
方法
使用基因组原位杂交（GISH）和流式细胞术来描述这些物种的基因组组成和分布，以及它们在英格兰南部南安普顿附近的埃林·马奇伍德和海斯的倍性水平。
结果
GISH 鉴定出在英国埃林·马奇伍德的一个非整倍体个体中，来自米草和互花米草的约 60 条染色体，来自互花米草的 62 条染色体和来自米草的 30 条染色体，在来自米草的个体中，鉴定出来自米草的约 60 条染色体和来自互花米草的 30 条染色体。GISH 和流式细胞术还表明，在海斯检查的大多数（94%）个体都是六倍体（其余两个个体（6%）是十二倍体；n=34），而在埃林·马奇伍德（n=22）发现六倍体（约 36%的植物）、非整倍体（约 27%）和十二倍体（约 36%）个体。
结论
非整倍体个体表明在六倍体和十二倍体物种之间存在基因渗入的可能性，这使得该属内的多倍体诱导物种形成的情况变得复杂。尽管米草具有侵略性的生态习性，但它并没有在海斯（同源杂种的频率为 94%，n=34）胜过米草（六倍体），尽管它们已经共存了 100 多年。GISH 的成功为未来研究该属内多倍体诱导的基因组重构提供了可能性。
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