Chen Xiao, Li Na, Liu Chenlu, Wang Hongtao, Li Yuxing, Xie Yuanmei, Ma Fengwang, Liang Jiakai, Li Cuiying
State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China.
Tree Physiol. 2022 Dec 12;42(12):2563-2577. doi: 10.1093/treephys/tpac096.
Drought stress is an important factor limiting apple production. γ-Aminobutyric acid (GABA) exists widely in plants and participates in the response to abiotic stress as a metabolite or signaling molecule. The role of exogenous GABA in apple plants, response to long-term drought stress remains unclear. Our study confirmed that exogenous GABA affects the drought resistance of apple plants under long-term drought stress. We found that 1 mM exogenous GABA improved the resistance of apple seedlings to long-term drought stress. The plants showed better growth, less reactive oxygen radical accumulation, less damage to cell membranes and greater active photosynthetic capacity. Under long-term drought stress, exogenous GABA facilitated GABA shunt, resulting in more accumulation of organic acids, namely citric acid, succinic acid and malic acid, in roots and stems of apple seedlings. In addition, exogenous GABA upregulated the expression of cellulose-related genes and lignin-related genes, and activated secondary cell wall-related transcription factors to synthesize more cellulose and lignin. A multiple factorial analysis confirmed that the GABA shunt and the biosynthesis of cellulose and lignin substantially contributed to the growth of apple seedlings with the application of exogenous GABA under long-term drought stress. Our results suggested that exogenous GABA improved the resistance of apple seedlings to long-term drought stress by enhancing GABA shunt and secondary cell wall biosynthesis.
干旱胁迫是限制苹果产量的重要因素。γ-氨基丁酸（GABA）广泛存在于植物中，作为一种代谢产物或信号分子参与非生物胁迫响应。外源GABA在苹果植株对长期干旱胁迫的响应中的作用尚不清楚。我们的研究证实，外源GABA影响长期干旱胁迫下苹果植株的抗旱性。我们发现1 mM外源GABA提高了苹果幼苗对长期干旱胁迫的抗性。植株表现出更好的生长状况、更少的活性氧自由基积累、对细胞膜的损伤更小以及更强的光合活性。在长期干旱胁迫下，外源GABA促进了GABA分流，导致苹果幼苗根和茎中有机酸（即柠檬酸、琥珀酸和苹果酸）积累更多。此外，外源GABA上调了纤维素相关基因和木质素相关基因的表达，并激活了次生细胞壁相关转录因子以合成更多的纤维素和木质素。多因素分析证实，在长期干旱胁迫下施用外源GABA时，GABA分流以及纤维素和木质素的生物合成对苹果幼苗的生长有显著贡献。我们的结果表明，外源GABA通过增强GABA分流和次生细胞壁生物合成提高了苹果幼苗对长期干旱胁迫的抗性。
