Naito Ken, Cho Eunyoung, Yang Guojun, Campbell Matthew A, Yano Kentaro, Okumoto Yutaka, Tanisaka Takatoshi, Wessler Susan R
Department of Plant Biology, University of Georgia, Athens, GA 30602, USA.
Proc Natl Acad Sci U S A. 2006 Nov 21;103(47):17620-5. doi: 10.1073/pnas.0605421103. Epub 2006 Nov 13.
Despite the prevalence of transposable elements in the genomes of higher eukaryotes, what is virtually unknown is how they amplify to very high copy numbers without killing their host. Here, we report the discovery of rice strains where a miniature inverted-repeat transposable element (mPing) has amplified from approximately 50 to approximately 1,000 copies in four rice strains. We characterized 280 of the insertions and found that 70% were within 5 kb of coding regions but that insertions into exons and introns were significantly underrepresented. Further analyses of gene expression and transposable-element activity demonstrate that the ability of mPing to attain high copy numbers is because of three factors: (i) the rapid selection against detrimental insertions, (ii) the neutral or minimal effect of the remaining insertions on gene transcription, and (iii) the continued mobility of mPingelements in strains that already have > 1,000 copies. The rapid increase in mPing copy number documented in this study represents a potentially valuable source of population diversity in self-fertilizing plants like rice.
尽管转座元件在高等真核生物基因组中普遍存在，但实际上人们对它们如何在不杀死宿主的情况下扩增到非常高的拷贝数却知之甚少。在此，我们报告了水稻品系的一项发现，其中一个微型反向重复转座元件（mPing）在四个水稻品系中从大约50个拷贝扩增到了大约1000个拷贝。我们对280个插入位点进行了特征分析，发现70%的插入位点位于编码区的5kb范围内，但外显子和内含子中的插入位点明显较少。对基因表达和转座元件活性的进一步分析表明，mPing能够达到高拷贝数的能力归因于三个因素：（i）对有害插入的快速选择，（ii）其余插入对基因转录的中性或最小影响，以及（iii）mPing元件在已经有超过1000个拷贝的品系中持续的移动性。本研究中记录的mPing拷贝数的快速增加代表了像水稻这样的自花授粉植物中种群多样性的一个潜在有价值的来源。
