γ-氨基丁酸调控高温下茄子种子萌发的机制研究

梁海婷; 张迎迎; 朱为民; 吴雪霞; 肖凯

γ-氨基丁酸调控高温下茄子种子萌发的机制研究

Eggplant Seed Germination Affected by Exogenous γ-Aminobutyric Acid under High Temperature

摘要

摘要:
目的研究高温胁迫下γ-氨基丁酸（Gamma-Aminobutyric Acid, GABA）影响茄子种子萌发的作用和机理。
方法以‘卜丽卡’为材料，设置不同浓度的GABA（0、0.5、1、3、5 mmol·L⁻¹）处理，明确其在高温胁迫下对种子萌发的作用，并以此为基础，选取最适浓度的GABA，进一步研究其对高温胁迫下茄子种子的萌发生理特性、内源激素含量和相关基因表达量的影响。
结果 38 ℃为种子萌发的临界高温阈值，选取37 ℃作为后续的试验温度。用不同浓度的GABA处理种子，发现0.5 mmol·L⁻¹处理6 d后发芽率提高了138.81%，将其作为后续试验浓度。与对照组相比，0.5 mmol·L⁻¹ GABA处理能显著提高种子发芽率、发芽势、发芽指数和胚根长度；增加脯氨酸、可溶性糖和可溶性蛋白的含量，提高超氧化物歧化酶（Superoxide, SOD）、过氧化物酶（Peroxidase, POD）和过氧化氢酶（Catalase, CAT）的活性，同时降低丙二醛（Malondialdehyde, MDA）和过氧化氢（Hydrogen Peroxide, H₂O₂）的积累。激素检测结果表明0.5 mmol·L⁻¹ GABA显著促进了内源激素赤霉素3（Gibberellin,GA₃）、赤霉素1（Gibberellin, GA₁）、赤霉素7（Gibberellin, GA₇）、茉莉酸-异亮氨酸（Jasmonoy-L-isoleucine, JA-Ile）和水杨酸（Salicylicacid，SA）的积累，同时降低脱落酸（Abscisic Acid，ABA）和吲哚乙酸（Indoleacetic Acid，IAA）的含量，茉莉酸(Jasmonic Acid, JA)含量在三天内无显著变化，但对比CK仍维持较高水平。对GA和ABA通路基因进行表达分析，发现0.5 mmol·L⁻¹ GABA上调了GA合成基因（GA20ox2、GA3ox1）、信号因子（GID1a、GID1b、GID1c）和ABA降解基因（CYP707A1、CYP707A2）的表达，下调了GA的降解基因（GA2ox1、GA2ox2）以及负调控因子della的表达，同时抑制了ABA的合成基因（NCED1、NCED2）及信号因子（ABI5、SnRK2.3）的表达。研究明确了0.5 mmol·L⁻¹ GABA通过多途径协同作用缓解高温抑制的最适浓度效应，为茄子抗逆栽培提供了理论依据和应用指导。
结论高温下通过0.5 mmol·L⁻¹的GABA处理茄子种子可以促进种子的萌发、提高耐热性，为茄子高温育苗生产提供了理论依据和应用指导。

Abstract:
Objective Effect of γ-aminobutyric acid (GABA) treatment on eggplant seed germination under high temperature was studied.
Methods Under high temperatures, GABA in the concentrations of 0, 0.5, 1, 3, or 5 mmol·L⁻¹ was added to observe ‘Bulika’ eggplant seed germination. With threshold temperature for germination determined, physiological characteristics, endogenous hormone secretion, and relevant gene expressions of the germinating seeds treated by GABA at varied concentrations were monitored.
Results The highest temperature the seeds could tolerated was found to be 38 ℃. To maximize the temperature effect below the threshold, 37℃ was selected for the experimentation. Since 0.5 mmol·L⁻¹ GABA raised the seed germination rate at 37 ℃ by 138.81% in 6d, the addition level was applied for the subsequent experiments. With the GABA treatment under heat stress, the seed germination potential and indicators were improved, the hypocotyls lengthened, the proline, soluble sugar, and protein contents enhanced, the Superoxide dismutase (SOD), Peroxidase (POD), and Catalase (CAT) activities elevated, and the Malondialdehyde (MDA) and Hydrogen Peroxide (H₂O₂) accumulations reduced over control. In addition, the endogenous hormones Gibberellin3 (GA₃), Gibberellin1 (GA₁), Gibberellin7 (GA₇), Jasmonoy-L-isoleucine (JA-Ile), and Salicylicacid (SA) rose significantly, abscisic acid (ABA) and Indoleacetic Acid (IAA) declined, and Jasmonic Acid (JA) remained high compared to CK in 3d. The expressions of GA synthesis genes (i.e., GA20ox2 and GA3ox1), signaling factors (i.e., GID1a, GID1b, and GID1c), and ABA degradation genes (i.e., CYP707A1 and CYP707A2) were upregulated, while the GA degradation genes (i.e., GA2ox1 and GA2ox2) and negative regulator della downregulated. Meanwhile, the ABA synthesis genes (i.e., NCED1 and NCED2) and signaling factors (i.e., ABI5 and SnRK2.3) were inhibited.
Conclusion Treating the eggplant seeds with 0.5 mmol·L⁻¹ of GABA stimulated germination and enhanced heat tolerance to 37℃ through a synergy of multi-pathways. Theoretically, the application could help accelerate eggplant seedling operation.

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