Malate exudation through wheat (Triticum aestivum L) aluminium‐activated malate transporter 1 (TaALMT1) confers Al³⁺ tolerance at low pH, but is also activated by alkaline pH, and is regulated by and facilitates significant transport of gamma‐aminobutyric acid (GABA, a zwitterionic buffer). Therefore, TaALMT1 may facilitate acidification of an alkaline rhizosphere by promoting exudation of both malate and GABA. Here, the performance of wheat near isogenic lines ET8 (Al⁺³‐tolerant, high TaALMT1 expression) and ES8 (Al⁺³‐sensitive, low TaALMT1 expression) are compared. Root growth (at 5 weeks) was higher for ET8 than ES8 at pH 9. ET8 roots exuded more malate and GABA at high pH and acidified the rhizosphere more rapidly. GABA and malate exudation was enhanced at high pH by the addition of aluminate in both ET8 and transgenic barley expressing TaALMT1. Xenopus laevis oocytes expressing TaALMT1 acidified an alkaline media more rapidly than controls corresponding to higher GABA efflux. TaALMT1 expression did not change under alkaline conditions but key genes involved in GABA turnover changed in accordance with a high rate of GABA synthesis. We propose that TaALMT1 plays a role in alkaline tolerance by exuding malate and GABA, possibly coupled to proton efflux.

中文翻译：

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TaALMT1苹果酸-GABA转运蛋白在小麦碱pH耐受性中的作用。

通过小麦苹果酸渗出（小麦L）铝活化苹果酸转运蛋白1（TaALMT1）赋予的Al ³⁺在低pH耐受性，而且还通过碱性pH活化的，并且通过调节和促进γ-氨基丁酸的显著运输（GABA ，两性离子缓冲液）。因此，TaALMT1可通过促进苹果酸和GABA的渗出而促进碱性根际的酸化。在此，等基因系ET8（耐Al ^{+ 3}，TaALMT1高表达）和ES8（耐Al ^{+ 3}，TaALMT1低）的小麦表现表达式）进行比较。在pH值为9的情况下，ET8的根生长（在5周时）高于ES8。在高pH值下，ET8的根分泌出更多的苹果酸和GABA，并更快地酸化了根际。在高pH条件下，通过在ET8和表达TaALMT1的转基因大麦中添加铝酸盐可以增强GABA和苹果酸的分泌。表达TaALMT1的非洲爪蟾卵母细胞比对应于较高GABA外排的对照更快地将碱性培养基酸化。在碱性条件下，TaALMT1的表达没有改变，但是与GABA转化有关的关键基因却随着GABA合成的高速率而改变。我们建议TaALMT1通过渗出苹果酸和GABA（可能与质子外流有关）在碱耐受中发挥作用。