Expression of aberrant forms of AUXIN RESPONSE FACTOR8 stimulates parthenocarpy in Arabidopsis and tomato
Expression of aberrant forms of AUXIN RESPONSE FACTOR8 stimulates parthenocarpy in Arabidopsis and tomato
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DOI：
10.1104/pp.107.104174
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发表时间：
2007-10-01
期刊：
影响因子：
7.4
通讯作者：
Koltunow, Anna M.
中科院分区：
文献类型：
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作者：
Goetz, Marc;Hooper, Lauren C.;Koltunow, Anna M.
拟南芥（Arabidopsis thaliana）的果实起始通常受到抑制，直到受精发生。然而，生长素响应因子 8 (ARF8) 的突变使果实起始与受精脱钩，导致形成无籽单性结实果实。在这里，我们通过植物转化引入突变基因组（g）Atarf8-4序列或gAtARF8：β-葡萄糖醛酸酶翻译融合构建体，在野生型拟南芥中诱导单性结实。没有观察到内源AtARF8转录的沉默，表明引入的异常ARF8转录物损害了内源ARF8和/或参与抑制果实起始的相关因子的功能。为了分析 ARF8 在番茄 (Solanum lycopersicum) 中的作用，我们首先对 23 个番茄品种进行去雄，以测试背景单性结实。令人惊讶的是，所有这些都具有启动不依赖受精的果实生长的倾向。 gAtarf8-4 在转基因番茄（“Monalbo”）中的表达导致单性结实果实的数量和大小显着增加。番茄 ARF8 cDNA 的分离表明 AtARF8 具有显着的序列保守性。因此，SlARF8 可能以与 AtARF8 在拟南芥中类似的方式控制番茄果实的形成。发现了两个大小相差 5 bp 的 SlARF8 cDNA，两者都源自同一基因。较小的 cDNA 是剪接变体，也存在于拟南芥中。我们提出，低内源水平的剪接变体产物可能会干扰抑制果实起始的复合物的有效形成/功能，从而为番茄和拟南芥去雄后观察到的子房扩张提供解释。增加异常 Atarf8-4 转录物的水平可能会以剂量依赖性方式进一步破坏复合物的形成/功能，从而增强番茄单性结实果实的起始频率和大小，并模仿纯合 Atarf8-4 突变体中发现的单性结实开裂长角果表型。总的来说，这些数据表明，涉及生长素信号传导的类似机制存在于抑制番茄和拟南芥中的单性结实。
Fruit initiation in Arabidopsis ( Arabidopsis thaliana) is generally repressed until fertilization occurs. However, mutations in AUXIN RESPONSE FACTOR8 (ARF8) uncouple fruit initiation from fertilization, resulting in the formation of seedless, parthenocarpic fruit. Here we induced parthenocarpy in wild-type Arabidopsis by introducing either the mutant genomic ( g) Atarf8-4 sequence or gAtARF8:beta-glucuronidase translational fusion constructs by plant transformation. Silencing of endogenous AtARF8 transcription was not observed, indicating that the introduced, aberrant ARF8 transcripts were compromising the function of endogenous ARF8 and/or associated factors involved in suppressing fruit initiation. To analyze the role of ARF8 in tomato ( Solanum lycopersicum) we initially emasculated 23 tomato cultivars to test for background parthenocarpy. Surprisingly, all had a predisposition to initiate fertilization-independent fruit growth. Expression of gAtarf8-4 in transgenic tomato ('Monalbo') resulted in a significant increase in the number and size of parthenocarpic fruit. Isolation of tomato ARF8 cDNA indicated significant sequence conservation with AtARF8. SlARF8 may therefore control tomato fruit initiation in a similar manner as AtARF8 does in Arabidopsis. Two SlARF8 cDNAs differing in size by 5 bp were found, both arising from the same gene. The smaller cDNA is a splice variant and is also present in Arabidopsis. We propose that low endogenous levels of the splice variant products might interfere with efficient formation/function of a complex repressing fruit initiation, thereby providing an explanation for the observed ovary expansion in tomato and also Arabidopsis after emasculation. Increasing the levels of aberrant Atarf8-4 transcripts may further destabilize formation/function of the complex in a dosage-dependent manner enhancing tomato parthenocarpic fruit initiation frequency and size and mimicking the parthenocarpic dehiscent silique phenotype found in homozygous Atarf8-4 mutants. Collectively these data suggest that similar mechanisms involving auxin signaling exist to inhibit parthenocarpic fruit set in tomato and Arabidopsis.