Graduate School of Nanobioscience, Yokohama City University, 1-7-29 Suehiro, Tsurumi, Yokohama 230-0045, Japan.
J Exp Bot. 2012 Sep;63(14):5301-10. doi: 10.1093/jxb/ers188. Epub 2012 Jul 21.
The phytohormone abscisic acid (ABA) plays pivotal roles in the regulation of developmental and environmental responses in plants. Identification of cytoplasmic ABA receptors enabled the elucidation of the main ABA signalling pathway, connecting ABA perception to either nuclear events or the action of several transporters. However, the physiological functions of ABA in cellular processes largely remain unknown. To obtain greater insight into the ABA response, genetic screening was performed to isolate ABA-related mutants of Arabidopsis and several novel ABA-hypersensitive mutants were isolated. One of those mutants--ahg11--was characterized further. Map-based cloning showed that AHG11 encodes a PPR type protein, which has potential roles in RNA editing. An AHG11-GFP fusion protein indicated that AHG11 mainly localized to the mitochondria. Consistent with this observation, the nad4 transcript, which normally undergoes RNA editing, lacks a single RNA editing event conferring a conversion of an amino acid residue in ahg11 mutants. The geminating ahg11 seeds have higher levels of reactive-oxygen-species-responsive genes. Presumably, partial impairment of mitochondrial function caused by an amino acid conversion in one of the complex I components induces redox imbalance which, in turn, confers an abnormal response to the plant hormone.
植物激素脱落酸（ABA）在植物发育和环境响应的调节中发挥着关键作用。细胞质 ABA 受体的鉴定使主要的 ABA 信号通路得以阐明，将 ABA 感知连接到核事件或几种转运蛋白的作用。然而，ABA 在细胞过程中的生理功能在很大程度上仍然未知。为了更深入地了解 ABA 反应，进行了遗传筛选以分离拟南芥的 ABA 相关突变体，并分离出几种新的 ABA 超敏突变体。其中一个突变体--ahg11--进一步进行了表征。基于图谱的克隆表明，AHG11 编码一种 PPR 型蛋白，它可能在 RNA 编辑中发挥作用。AHG11-GFP 融合蛋白表明 AHG11 主要定位于线粒体。与这一观察结果一致，nad4 转录本，通常经历 RNA 编辑，缺少一个赋予 ahg11 突变体中一个氨基酸残基转换的单个 RNA 编辑事件。萌发的 ahg11 种子具有更高水平的活性氧应答基因。可以推测，一种复合体 I 成分中的一个氨基酸转换导致的线粒体功能部分受损引起氧化还原失衡，从而对植物激素产生异常反应。
