背景回顾The aluminum (Al) cation Al3+ in acidic soil shows severe rhizotoxicity that inhibits plant growth and development. 

提出问题：Most woody plants adapted to acidic soils have evolved specific strategies against Al3+ toxicity, but the underlying mechanism remains elusive. 

研究对象1-GABA：The four-carbon amino acid gamma-aminobutyric acid (GABA) has been well studied in mammals as an inhibitory neurotransmitter; GABA also controls many physiological responses during environmental or biotic stress. 

研究对象2-杂交鹅掌楸：The woody plant hybrid Liriodendron (L. chinense × tulipifera) is widely cultivated in China as a horticultural tree and provides high-quality timber; studying its adaptation to high Al stress is important for harnessing its ecological and economic potential. 

结果1-杂交鹅掌楸铝胁迫下的蛋白变化：Here, we performed quantitative iTRAQ (isobaric tags for relative and absolute quantification) to study how protein expression is altered in hybrid Liriodendron leaves subjected to Al stress. Hybrid Liriodendronshows differential accumulation of several proteins related to cell wall biosynthesis, sugar and proline metabolism, antioxidant activity, cell autophagy, protein ubiquitination degradation, and anion transport in response to Al damage. 

结果2-铝胁迫增加GABA生物合成：We observed that Al stress upregulated glutamate decarboxylase (GAD) and its activity, leading to increased GABA biosynthesis. 

结果3-GABA处理增强铝胁迫耐受性及分子机制：Additional GABA synergistically increased Al-induced antioxidant enzyme activity to efficiently scavenge ROS, enhanced proline biosynthesis, and upregulated the expression of MATE1/2, which subsequently promoted the efflux of citrate for chelation of Al3+. 

结果4-拟南芥中存在类似现象：We also showed similar effects of GABA on enhanced Al3+ tolerance in Arabidopsis. 

结论：Thus, our findings suggest a function of GABA signaling in enhancing hybrid Liriodendron tolerance to Al stress through promoting organic acid transport and sustaining the cellular redox and osmotic balance.

 摘 要 

酸性土壤中的铝离子对于植物的根具有毒性，严重抑制植物生长和发育。大多数适应于酸性土壤的木本植物演化出了独特的耐铝毒策略，但是具体的分子机制还不清楚。四碳氨基酸γ-氨基丁酸（GABA）作为一种抑制性神经递质，在哺乳动物中研究得比较广泛；同时，GABA还控制着环境或生物胁迫下的许多生理反应。木本植物杂种鹅掌楸是我国广泛栽培的一种园艺树种，木材优良，研究其对高铝胁迫的适应性对开发其生态和经济潜力具有重要意义。本文中，作者进行了定量iTRAQ来研究在铝胁迫下，杂交鹅掌楸叶片中的蛋白表达变化。杂交鹅掌楸叶片中与细胞壁生物合成、糖和脯氨酸代谢、抗氧化活性、细胞自噬、蛋白质泛素化降解及阴离子转运相关的多种蛋白表现出差异性积累。作者进一步发现铝胁迫会上调谷氨酸脱羧酶（GAD）及其活性，导致GABA生物合成的增加。额外的GABA协同增加Al诱导的抗氧化酶活性，从而有效清除ROS，增强了脯氨酸的生物合成，并上调MATE1/2的表达，从而促进柠檬酸盐的外排以螯合铝离子。作者还发现GABA在增强拟南芥对铝离子的耐受性方面具有类似的作用。因此，本文的研究结果表明，GABA信号通过促进有机酸转运和维持细胞氧化还原及渗透平衡，来增强杂交鹅掌楸对铝胁迫的耐受性。