來自葡萄牙IGC研究所和紐約冷泉港實驗室的科學家們已經(jīng)描述出植物花粉粒中預防轉(zhuǎn)座子引起的突變的機制,。
轉(zhuǎn)座子或跳躍基因在現(xiàn)有的基因組中十分常見,。例如，轉(zhuǎn)座子在玉米基因組內(nèi)比例超過70%,。激活轉(zhuǎn)座子可能會引起有害的突變,，因此，轉(zhuǎn)座子的激活需要嚴格控制,。如果類似的有害突變發(fā)生在有性生殖細胞中,，會將損害傳遞給下一代并蔓延至整個族群。
在花粉粒中,，精細胞是由大型的伴細胞保護的,。伴細胞向精細胞提供能量和營養(yǎng)物質(zhì)，并在授精過程中推動其向目標前進?？茖W家們發(fā)現(xiàn),，伴細胞也向精細胞提供指示，使其DNA免受損害,，從而幫助精細胞穩(wěn)定地傳遞基因組信息至下一代,。這種提示是以小干擾RNAs（siRNA）的形式存在的，通過RNA干擾使轉(zhuǎn)座子沉默,。（生物谷Bioon.com）
生物谷推薦原始出處：
Cell, 6 February 2009 doi:10.1016/j.cell.2008.12.038
Epigenetic Reprogramming and Small RNA Silencing of Transposable Elements in Pollen
R. Keith Slotkin1,Matthew Vaughn1,Filipe Borges2,Miloš Tanurdžić1,Jörg D. Becker2,José A. Feijó2,3and Robert A. Martienssen1
1 Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA
2 Instituto Gulbenkian de Ciencia, Centro de Biologia de Desenvolvimento, 2780-901 Oeiras, Portugal
3 Departamento de Biologia Vegetal, Faculdade de Ciencias da Universidade de Lisboa, Lisboa, 1700 Campo Grande, Portugal
The mutagenic activity of transposable elements (TEs) is suppressed by epigenetic silencing and small interfering RNAs (siRNAs), especially in gametes that couldtransmit transposed elements to the next generation. In pollen from the model plant Arabidopsis, we show that TEs are unexpectedly reactivated and transpose, but only in the pollen vegetative nucleus, which accompanies the sperm cells but does not provide DNA to the fertilized zygote. TE expression coincides with downregulation of the heterochromatin remodeler DECREASE IN DNA METHYLATION 1 and of many TE siRNAs. However, 21 nucleotide siRNAs from Athila retrotransposons are generated and accumulate in pollen and sperm, suggesting that siRNA from TEs activated in the vegetative nucleus can target silencing in gametes. We propose a conserved role for reprogramming in germline companion cells, such as nurse cells in insects and vegetative nuclei in plants, to reveal intact TEs in the genome and regulate their activity in gametes.
