在11月13日的《美国科学院院刊》网站上公示了来自美国新泽西大学的华裔学者王清华(Qinghua Wang,音译,文章第一作者)和Hugo K. Dooner的有关玉米基因组结构变异的最新研究成果。
玉米可能是所有农作物中最多样化的物种。通过比较两种不同的玉米自交系McC和B73的(inbred lines)bz基因组区域,研究人员以外地发现了大量的单模标本差异。
构成了玉米中多数DNA成分的反转录转座子簇在构成上有明显的变化并且在基因中的相对位置也有明显变化。
这些Corn Belt自交系的等位bz区域只具占所有序列的少数。为了进一步分析由反转录转座子、helitrons和其他插入形式,研究人员分析了另外5种品系玉米中的bz基因组区域。这五种分别为自交系A188、CML258和I137TN以及land races Coroico和NalTel。
这种垂直比较揭示出存在几种新的helitrons、反转录转座子、每个DNA转座子超家族成员、大量的微笑成分和新的插入成分——TAFT(TA-flanked transposons)。
通过垂直比较和成对比较,研究人员推测共有基因空间的重组极大地增加了玉米祖先中反转录转座扩增产生的变异性,从而创造出现代玉米中基因组构成异质性特征。
部分英文原文:
Unprecedented Haplotype Variability In The Maize bz Genomic Region
A comparison of the bz genomic regions of lines McC and B73, the selected standard for sequencing the maize genome, showed unexpected polymorphisms in the size and make-up of retrotransposon clusters at “allelic” positions, in the pattern of interspersion of genes and retrotransposons in the region, and in the gene content of the bz genomic region. Four genes, all members of small gene families, are located next to each other in line McC, but are missing from the corresponding location in line B73. Those four genes, either in one or two fragments, appear to be present elsewhere in the B73 genome. Additional sequencing of the bz genomic region from other inbred lines has identified common haplotypes and chimeric haplotypes. Chimeric haplotypes have retrotransposon clusters found in different haplotypes. Recombination in the gene space shared by different haplotypes shuffles retrotransposon clusters, creating huge heterogeneity in genome organization among modern maize lines. The observed intraspecific violation of genetic colinearity has potential implications regarding the breeding behavior of maize inbreds and hybrids.