Section of Cell and Developmental Biology, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0116, USA.
Mol Plant. 2013 Mar;6(2):539-45. doi: 10.1093/mp/sss093. Epub 2012 Sep 12.
T-DNA insertion mutants have been widely used to define gene functions in Arabidopsis and in other plants. Here, we report an unexpected phenomenon of epigenetic suppression of T-DNA insertion mutants in Arabidopsis. When the two T-DNA insertion mutants, yuc1-1 and ag-TD, were crossed together, the defects in all of the ag-TD plants in the F2 population were partially suppressed regardless of the presence of yuc1-1. Conversion of ag-TD to the suppressed ag-TD (named as ag-TD*) did not follow the laws of Mendelian genetics. The ag-TD* could be stably transmitted for many generations without reverting to ag-TD, and ag-TD* had the capacity to convert ag-TD to ag-TD*. We show that epigenetic suppression of T-DNA mutants is not a rare event, but certain structural features in the T-DNA mutants are needed in order for the suppression to take place. The suppressed T-DNA mutants we observed were all intronic T-DNA mutants and the T-DNA fragments in both the trigger T-DNA as well as in the suppressed T-DNA shared stretches of identical sequences. We demonstrate that the suppression of intronic T-DNA mutants is mediated by trans-interactions between two T-DNA insertions. This work shows that caution is needed when intronic T-DNA mutants are used.
T-DNA 插入突变体已被广泛用于定义拟南芥和其他植物中的基因功能。在这里，我们报道了拟南芥 T-DNA 插入突变体的表观遗传抑制的一个意外现象。当两个 T-DNA 插入突变体，yuc1-1 和 ag-TD，杂交在一起时，F2 群体中所有 ag-TD 植物的缺陷都被部分抑制，而不管 yuc1-1 的存在与否。ag-TD 向受抑制的 ag-TD（称为 ag-TD*）的转化并不遵循孟德尔遗传规律。ag-TD可以稳定地传递许多代而不恢复为 ag-TD，并且 ag-TD有能力将 ag-TD 转化为 ag-TD*。我们表明，T-DNA 突变体的表观遗传抑制不是一个罕见的事件，但为了发生抑制，T-DNA 突变体需要具有某些结构特征。我们观察到的受抑制的 T-DNA 突变体都是内含子 T-DNA 突变体，触发 T-DNA 和受抑制 T-DNA 中的 T-DNA 片段都共享相同序列的延伸。我们证明内含子 T-DNA 突变体的抑制是由两个 T-DNA 插入之间的转相互作用介导的。这项工作表明，在使用内含子 T-DNA 突变体时需要谨慎。
