Spontaneous mutations caused by a Helitron transposon, Hel-It1, in morning glory, Ipomoea tricolor
Spontaneous mutations caused by a Helitron transposon, Hel-It1, in morning glory, Ipomoea tricolor
复制标题
DOI：
10.1111/j.1365-313x.2006.03007.x
复制
发表时间：
2007-03-01
期刊：
影响因子：
7.2
通讯作者：
Iida, Shigeru
中科院分区：
文献类型：
--
作者：
Choi, Jeong-Doo;Hoshino, Atsushi;Iida, Shigeru
Helitrons是真核DNA转座子中的新成员，最初是通过计算分析在拟南芥、水稻和线虫的基因组中鉴定出来的。它们的结构特征与其他转座子不同，它们的转座机制参与了滚环复制。计算机预测的具有保守末端序列5‘-TC和CTRR-3’的自主氦被认为编码一个假定的转座酶Rep/Hel-TPase，它包含一个复制起始蛋白(Rep)的特征核酸酶/连接酶结构域和一个DNA解旋酶结构域(Hel)。植物Helitrons被认为编码一个额外的转座酶，RPA-TPase，它与复制蛋白A(RPA70)的最大亚基相关。尽管在不同的基因组中发现了氦电子，但既没有自主元件，也没有转座事件的报道。在这里，我们展示了一个自发的三色通菜珍珠S突变体。珍珠盖茨大约在1940年被分离出来，表现出白色的花朵，它有一个11.5kbp的新颖的Helitron，命名为Hel-IT1，整合到DFR-B基因中，用于花青素的着色。HEL-IT1显示了预测的植物Heliton结构，该结构具有保守的末端，并携带两个假定的转座酶基因Rep/Hel-TPase和RPA-TPase，分别包含一个无义突变和一个移码突变。HEL-IT1相关元件散布在通菜基因组中，只有一小部分珍珠-S植株在另一个插入位点携带HEL-IT1。珍珠-S突变体似乎带有一个自主元件，并表达野生型RPA-TPase转录本。讨论了一个可能的自主元件及其转座酶基因的结构。
Helitrons are newcomers among eukaryotic DNA transposons and have originally been identified by computational analysis in the genomes of Arabidopsis, rice and nematode. They are distinguished from other transposons in their structural features, and their proposed transposition mechanisms are involved in rolling circle replication. Computer-predicted autonomous Helitrons with conserved terminal sequences 5'-TC and CTRR-3' are presumed to encode a putative transposase, Rep/Hel-TPase, which contains a characteristic nuclease/ligase domain for the replication-initiation protein (Rep) and a DNA helicase domain (Hel). Plant Helitrons are thought to encode an additional transposase, RPA-TPase, which is related to the largest subunit of the replication protein A (RPA70). Although Helitrons are found in diverse genomes, neither an autonomous element nor a transposition event has been reported. Here we show that a spontaneous pearly-s mutant of Ipomoea tricolor cv. Pearly Gates, exhibiting white flowers and isolated in approximately 1940, has an 11.5-kbp novel Helitron, named Hel-It1, integrated into the DFR-B gene for anthocyanin pigmentation. Hel-It1 shows the predicted plant Helitron structure for an autonomous element with the conserved termini and carrying the two putative transposase genes, Rep/Hel-TPase and RPA-TPase, which contain a nonsense and a frameshift mutation, respectively. Hel-It1-related elements are scattered in the Ipomoea genome, and only a fraction of the pearly-s plants were found to carry Hel-It1 at another insertion site. The pearly-s mutant appears to bear an autonomous element and to express the wild-type RPA-TPase transcripts. The structures of a putative autonomous element and its transposase genes are discussed.