GENETIC BASIS FOR A RARE FLORAL MUTANT IN AN ANDEAN SPECIES OF SOLANACEAE
GENETIC BASIS FOR A RARE FLORAL MUTANT IN AN ANDEAN SPECIES OF SOLANACEAE
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DOI：
10.3732/ajb.1400395
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发表时间：
2015-02-01
影响因子：
3
通讯作者：
Smith, Stacey D.
中科院分区：
文献类型：
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作者：
Coburn, Rachel A.;Griffin, Randi H.;Smith, Stacey D.
研究前提：典型色素花的白色形式是开花植物中最常见的多态性之一。尽管从模型系统中已知产生白色表型的遗传变化范围，但很少有研究确定自然群体中的致病突变。方法：在这里，我们结合遗传研究、体外酶测定和生化分析来确定天然存在的白花萼花中花青素产量丧失的机制 （茄科）。关键结果：花青素基因序列的比较揭示了白色品种中假定的功能丧失突变，即二氢黄酮醇 4-还原酶 (DFR) 中的 11 个氨基酸缺失。对蓝色和白色变体的 Dfr 等位基因的功能分析表明，这种缺失导致酶活性丧失，表明这种缺失可能是色素产生缺乏的唯一原因。与这一假设一致，定量 PCR 显示不同形态之间花青素基因的表达没有显着差异。此外，薄层色谱证实白色变体继续在 DFR 酶上游积累化合物。结论：总的来说，这些实验表明 Dfr 的结构突变是 Iochroma calycinum 罕见的白花变体的基础。这项研究是花色多态性是由于花青素酶编码区功能丧失突变引起的少数例子之一。自然界中此类突变的罕见性表明，负面后果阻碍了人群之间的固定。
Premise of the study: White forms of typically pigmented flowers are one of the most common polymorphisms in flowering plants. Although the range of genetic changes that give rise to white phenotypes is well known from model systems, few studies have identified causative mutations in natural populations.Methods: Here we combine genetic studies, in vitro enzyme assays, and biochemical analyses to identify the mechanism underlying the loss of anthocyanin pigment production in the naturally occurring white-flowered morph of Iochroma calycinum (Solanaceae).Key results: Comparison of anthocyanin gene sequences revealed a putative loss-of-function mutation, an 11 amino-acid deletion in dihydroflavonol 4-reductase (DFR), in the white morph. Functional assays of Dfr alleles from blue and white morphs demonstrated that this deletion results in a loss of enzymatic activity, indicating that the deletion could be solely responsible for the lack of pigment production. Consistent with this hypothesis, quantitative PCR showed no significant differences in expression of anthocyanin genes between the morphs. Also, thin layer chromatography confirmed that the white morph continues to accumulate compounds upstream of the DFR enzyme.Conclusions: Collectively, these experiments indicate that the structural mutation at Dfr underlies the rare white flower morph of Iochroma calycinum. This study is one of only a few examples where a flower color polymorphism is due to a loss-of-function mutation in the coding region of an anthocyanin enzyme. The rarity of such mutations in nature suggests that negative consequences prevent fixation across populations.