來自葡萄牙IGC研究所和紐約冷泉港實(shí)驗(yàn)室的科學(xué)家們已經(jīng)描述出植物花粉粒中預(yù)防轉(zhuǎn)座子引起的突變的機(jī)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(huì)引起有害的突變,，因此，轉(zhuǎn)座子的激活需要嚴(yán)格控制,。如果類似的有害突變發(fā)生在有性生殖細(xì)胞中,，會(huì)將損害傳遞給下一代并蔓延至整個(gè)族群。
在花粉粒中,，精細(xì)胞是由大型的伴細(xì)胞保護(hù)的,。伴細(xì)胞向精細(xì)胞提供能量和營(yíng)養(yǎng)物質(zhì)，并在授精過程中推動(dòng)其向目標(biāo)前進(jìn),?？茖W(xué)家們發(fā)現(xiàn)，伴細(xì)胞也向精細(xì)胞提供指示，使其DNA免受損害,，從而幫助精細(xì)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.
