Furner I J, Sheikh M A, Collett C E
Department of Genetics, University of Cambridge, Cambridge CB2 3EH, United Kingdom.
Genetics. 1998 Jun;149(2):651-62. doi: 10.1093/genetics/149.2.651.
Transgenes inserted into the plant genome can become inactive (gene silencing) or result in silencing of homologous cellular genes [homology-dependent gene silencing (HDG silencing)]. In an earlier study we reported HDG silencing of chalcone synthase (CHS) in Arabidopsis. This study concerns genetic revertants of one of the CHS HDG-silencing transgenic homozygotes. Two monogenic recessive trans-acting mutations (hog1 and ddm1) that impair gene silencing and HDG silencing were identified. These mutations reduce genomic DNA methylation and affect the quantity and size of CHS mRNA. These results imply that DNA methylation is necessary for both gene silencing and HDG silencing. Two further monogenic, trans-acting, recessive mutations (sil1 and sil2) reduce gene silencing but not HDG silencing. The existence of this mutant class shows that gene silencing involves genes that are not necessary for HDG silencing. A further mutant (Catt) was isolated and has an attenuated HDG-silencing T-DNA.
插入植物基因组的转基因可能会变得无活性（基因沉默），或导致同源细胞基因沉默[同源依赖性基因沉默（HDG沉默）]。在早期的一项研究中，我们报道了拟南芥中查尔酮合酶（CHS）的HDG沉默。本研究涉及其中一个CHS HDG沉默转基因纯合子的遗传回复体。鉴定出了两个损害基因沉默和HDG沉默的单基因隐性反式作用突变（hog1和ddm1）。这些突变减少了基因组DNA甲基化，并影响CHS mRNA的数量和大小。这些结果表明，DNA甲基化对于基因沉默和HDG沉默都是必需的。另外两个单基因、反式作用、隐性突变（sil1和sil2）减少了基因沉默，但没有减少HDG沉默。这类突变体的存在表明，基因沉默涉及HDG沉默所不需要的基因。另外分离出了一个突变体（Catt），其HDG沉默T-DNA减弱。
