State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou, 310058, China.
Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, Tea Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou, 310008, China.
Plant Cell Environ. 2018 Apr;41(4):809-822. doi: 10.1111/pce.13150. Epub 2018 Feb 22.
Aluminum (Al)-induced organic acid secretion from the root apex is an important Al resistance mechanism. However, it remains unclear how plants fine-tune root organic acid secretion which can contribute significantly to the loss of fixed carbon from the plant. Here, we demonstrate that Al-induced citrate secretion from the rice bean root apex is biphasic, consisting of an early phase with low secretion and a later phase of large citrate secretion. We isolated and characterized VuMATE2 as a possible second citrate transporter in rice bean functioning in tandem with VuMATE1, which we previously identified. The time-dependent kinetics of VuMATE2 expression correlates well with the kinetics of early phase root citrate secretion. Ectopic expression of VuMATE2 in Arabidopsis resulted in increased root citrate secretion and Al resistance. Electrophysiological analysis of Xenopus oocytes expressing VuMATE2 indicated VuMATE2 mediates anion efflux. However, the expression regulation of VuMATE2 differs from VuMATE1. While a protein translation inhibitor suppressed Al-induced VuMATE1 expression, it releases VuMATE2 expression. Yeast one-hybrid assays demonstrated that a previously identified transcription factor, VuSTOP1, interacts with the VuMATE2 promoter at a GGGAGG cis-acting motif. Thus, we demonstrate that plants adapt to Al toxicity by fine-tuning root citrate secretion with two separate root citrate transport systems.
铝（Al）诱导根尖有机酸分泌是一种重要的耐铝机制。然而，目前尚不清楚植物如何精细调节根有机酸分泌，因为这会显著导致植物固定碳的损失。在这里，我们证明了水稻根根尖的柠檬酸分泌是双相的，由早期低分泌相和后期大量柠檬酸分泌相组成。我们分离并鉴定 VuMATE2 为可能的第二个柠檬酸转运蛋白，与我们之前鉴定的 VuMATE1 协同作用。VuMATE2 表达的时程与早期根尖柠檬酸分泌的时程很好地相关。在拟南芥中异位表达 VuMATE2 导致根柠檬酸分泌增加和耐铝性增强。表达 VuMATE2 的非洲爪蟾卵母细胞的电生理学分析表明，VuMATE2 介导阴离子外排。然而，VuMATE2 的表达调控与 VuMATE1 不同。虽然蛋白翻译抑制剂抑制 Al 诱导的 VuMATE1 表达，但它释放 VuMATE2 的表达。酵母单杂交试验表明，先前鉴定的转录因子 VuSTOP1 在 GGGAGG 顺式作用元件处与 VuMATE2 启动子相互作用。因此，我们证明植物通过两个独立的根柠檬酸转运系统来精细调节根柠檬酸分泌，从而适应铝毒性。
