The maternally expressed WRKY transcription factor TTG2 controls lethality in interploidy crosses of Arabidopsis.
The maternally expressed WRKY transcription factor TTG2 controls lethality in interploidy crosses of Arabidopsis.
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DOI：
10.1371/journal.pbio.0060308
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发表时间：
2008-12-09
期刊：
影响因子：
9.8
通讯作者：
Comai L
中科院分区：
文献类型：
--
作者：
Dilkes BP;Spielman M;Weizbauer R;Watson B;Burkart-Waco D;Scott RJ;Comai L
不同亲本之间的 F1 杂种致死性的分子机制是物种形成研究的目标之一。相同基因型的二倍体和四倍体个体之间的杂交可导致F1致死，并且这种剂量敏感的不相容性在多倍体物种形成中发挥作用。我们已经鉴定了拟南芥间倍体杂交中 F1 致死率的变异，并通过 QTL 作图确定了母本表达变异的遗传结构。单个大效应QTL，DR。鉴定出 STRANGELOVE 1 (DSL1) 以及两个与 DSL1 具有上位关系的 QTL。 DSL1 通过在母体孢子体中的表达影响合子后致死率。精细定位将 DSL1 置于编码母体效应转录因子 TTG2 的区间内。携带 TTG2 功能丧失突变的母本抑制了父系过度倍体间杂交引起的 F1 致死率。胚乳细胞化的频率同样受到自然变异和 ttg2 功能丧失突变体的影响。自然变异和单基因突变效应的简单遗传基础表明，多倍体中的 F1 致死性可能会迅速进化。此外，孢子体活性TTG2基因在间倍性杂交中的作用表明，母体的发育编程调节间倍性杂种后代的生存能力。许多开花植物能够耐受基因组拷贝数（倍性）的变化，但具有不同倍性的亲本的后代通常无法发育。我们研究了拟南芥中的这种现象，发现了倍体间交配生存能力的变化。当二倍体雌性与 Col 的四倍体雄性交配时，两种常见品系（称为种质）Ler 和 Col 分别是允许的和不耐受的。我们绘制了负责这种反应的基因，并确定了一个主要基因座，我们将其称为 DR。 STRANGELOVE1位于2号染色体上，经过更精细的作图，将位点TRANSPARENT TESTA GLABRA2 (TTG2)定义为候选基因。 TTG2 调节倍体间杂交的命运，TTG2 的敲除改善了 Ler 和 Col 中倍体性交配的结果。此外，这两个品种在基因型和该基因的表达方面存在差异。 TTG2 是一种表皮调节剂，其活性影响种子胚乳发育。重要的是，TTG2 在种子植物的组织内起作用，表明跨代相互作用负责控制倍体间交配的结果。二倍体和四倍体（具有全基因组重复的植物）之间的杂交致死率是由包裹种子的母体组织中表达的表皮调节因子决定的。
The molecular mechanisms underlying lethality of F1 hybrids between diverged parents are one target of speciation research. Crosses between diploid and tetraploid individuals of the same genotype can result in F1 lethality, and this dosage-sensitive incompatibility plays a role in polyploid speciation. We have identified variation in F1 lethality in interploidy crosses of Arabidopsis thaliana and determined the genetic architecture of the maternally expressed variation via QTL mapping. A single large-effect QTL, DR. STRANGELOVE 1 (DSL1), was identified as well as two QTL with epistatic relationships to DSL1. DSL1 affects the rate of postzygotic lethality via expression in the maternal sporophyte. Fine mapping placed DSL1 in an interval encoding the maternal effect transcription factor TTG2. Maternal parents carrying loss-of-function mutations in TTG2 suppressed the F1 lethality caused by paternal excess interploidy crosses. The frequency of cellularization in the endosperm was similarly affected by both natural variation and ttg2 loss-of-function mutants. The simple genetic basis of the natural variation and effects of single-gene mutations suggests that F1 lethality in polyploids could evolve rapidly. Furthermore, the role of the sporophytically active TTG2 gene in interploidy crosses indicates that the developmental programming of the mother regulates the viability of interploidy hybrid offspring. Many flowering plants tolerate changes in the number of genome copies (ploidy), but offspring of parents with different ploidies often fail to develop. We investigated this phenomenon in Arabidopsis thaliana and discovered variation in the ability to survive interploidy matings. Two common strains (known as accessions), Ler and Col, are respectively permissive and intolerant when diploid females are mated to tetraploid males of Col. We mapped the genes responsible for this response and identified a major locus, which we call DR. STRANGELOVE1, on chromosome 2, and after finer mapping, defined the locus TRANSPARENT TESTA GLABRA2 (TTG2) as the candidate gene. TTG2 regulates the fate of interploidy crosses, and knock-outs of TTG2 improved the outcome of interploidy matings in both Ler and Col. Furthermore, the two accessions differed in genotype and in expression of this gene. TTG2 is an epidermal regulator whose activity affects seed endosperm development. Importantly, TTG2 acts within tissue of the seed-plant, indicating that a transgenerational interaction is responsible for controlling the outcome of interploidy mating. Hybrid lethality in crosses between diploids and tetraploids, plants with whole genome duplication, is determined by an epidermal regulator expressed in the maternal tissue that envelops the seed.
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