γ-氨基丁酸（GABA）调控盐胁迫下玉米种子萌发和幼苗生长的机制

发布时间：2018-01-02 18:09

本文关键词：γ-氨基丁酸（GABA）调控盐胁迫下玉米种子萌发和幼苗生长的机制　出处：《东北农业大学》2016年博士论文　论文类型：学位论文

【摘要】：玉米是我国重要的粮食和饲料作物,在国民经济中占有重要的地位。盐渍化土壤是一种广泛分布的低产土壤,是造成世界范围内作物减产的主要环境因子之一。盐胁迫会影响作物正常的生长发育,而玉米又是中度盐敏感型作物,盐胁迫会严重影响玉米的生理代谢,从而直接影响玉米的生长发育和产量品质形成。为了探究γ-氨基丁酸(GABA)提高玉米耐盐性的机制,本论文选择两种耐盐性不同的玉米为试验材料,研究盐胁迫下GABA对种子萌发、幼苗生长、抗氧化酶系统、氮代谢、内源激素含量、光合系统和基因差异化表达的影响,旨在明确GABA提高玉米耐盐能力的生理途径和由其诱导的差异表达基因的相关功能及与耐盐性的关系。试验于2014年和2015年在东北农业大学农学院温室进行,选用耐盐型玉米品种郑单958和盐敏感型玉米品种东农253为供试品种,转录组测序采用郑单958父本昌7-2。通过前期试验筛选,种子萌发的Na Cl胁迫浓度定为100 mmol/L,幼苗生长的Na Cl胁迫浓度为150mmol/L。试验GABA的施用浓度分别为0、0.25、0.5、1和2 mmol/L。种子萌发试验采用与试验设置对应浓度的溶液为萌发基质进行发芽试验,水培介质选用1/2霍格兰营养液,当玉米幼苗生长到三叶一心时,对幼苗进行处理。主要研究结果如下:(1)施用一定浓度的GABA能有效的缓解Na Cl造成的萌发抑制现象。Na Cl胁迫下,0.5mmol/L GABA处理的郑单958和东农253种子的发芽率、发芽势、活力指数和贮藏物质转运率分别比单独Na Cl胁迫处理的种子高。0.5 mmol/L GABA处理种子对于缓解Na Cl胁迫对胚根长和胚芽鞘长抑制作用效果最好,与单独Na Cl胁迫相比郑单958胚根和胚芽鞘长分别升高了46.76%和49.69%;东农253为58.52%和45.14%。GABA处理能显著的提高α-淀粉酶的活性,从而促进种子的萌发,其中0.5 mmol/L GABA效果最好。(2)一定浓度的GABA都能缓解Na Cl胁迫对幼苗生长的抑制,有利于幼苗形态建成。GABA处理植株的株高和茎叶干鲜重都高于单独Na Cl处理的植株,其中GABA浓度为0.5mmol/L的处理效果好于其他GABA处理。GABA缓解Na Cl胁迫对东农253的生长抑制的效果好于郑单958。GABA能提高Na Cl胁迫下根系干鲜重的积累,增加根系总长度、根表面、根体积和根尖数,降低根系平均直径。通过根系扫描图片可知,0.5 mmol/L GABA有利于根毛的生成,这促进了Na Cl胁迫下根系水分和养分的吸收,是玉米幼苗生长良好的重要保证。(3)一定浓度的GABA能有效的降低盐胁迫下叶片内的MDA和O2·-含量,其中0.5mmol/L的GABA效果最佳。Na Cl胁迫会显著的提高超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性以便清除体内的MDA和O2·-,GABA能进一步提高抗氧化酶活性,其中0.5 mmol/L的GABA效果最佳。(4)外源施加GABA也能提高幼苗叶片和根系的内源GABA含量。在正常生长和Na Cl胁迫条件下,GABA均能提高叶片和根系内的可溶性蛋白含量,降低丙酮酸含量。外源GABA加入后会产生GABA的反馈调节,使得GAD活性降低。GAD活性降低会导致谷氨酸含量升高,从而又会反馈调节GS、GOGAT和GDH活性,使其活性降低。通过反馈调控作用会使得氮代谢的进程中各种物质间的转化趋于稳定,因此会使得可溶性蛋白水解减少,而丙酮酸可更好的参与其他代谢物质的生成,因此含量下降。(5)NaCl胁迫下,叶片和根系内的ABA含量会明显升高,这有利于植株提高抗性。由于ABA是抑制生长型激素,并且它与促生长型激素有拮抗作用,所以叶片和根系内的IAA、GA和ZR含量下降,从表型上看则表现为生长量下降。外源GABA的加入能改善植株多种代谢,如提高抗氧化酶系统,从而减少了胁迫带来的损伤,因此GABA处理的植株的ABA含量下降,IAA、GA和ZR含量上升,从表型上看表现为植株恢复生长。(6)外源GABA的加入能降低Na Cl胁迫对叶片造成的损伤,减少叶绿素的分解,从而提高SPAD值、光合速率、蒸腾速率和气孔导度。改善植株光合作用会提高CO2的利用率,使胞间CO2浓度出现下降或者平稳的趋势。(7)通过转录组测序的分析,得到了盐胁迫下GABA诱导的差异表达的基因,通过基因功能对比,选取了与试验生理指标相关的差异表达基因。在上调表达的基因中,有调控过氧化物酶体生物合成蛋白质的基因,有调控生长素响应因子的基因,有调控LHCII型叶绿素a、b结合蛋白的基因。在下调表达的转录子中,有调控谷氨酸合成酶的基因,有调控吲哚-3-乙醛氧化酶,有调控脱落酸应答的基因。这些基因的上调或下调表达会引起与其对应的生理指标发生变化,从而在分子层面揭示在Na Cl胁迫下GABA的功能和作用。
[Abstract]:Maize is an important food and feed crops, occupies an important position in the national economy. The soil salinization is a widely distributed soil and low yield, which is one of the main environmental factors in the world crop production. Salt stress will influence the normal growth and development of crops, maize is also moderately salt sensitive crops. Salt stress seriously affects the physiological metabolism of maize, which directly affect the formation of maize growth and yield and quality. In order to explore the gamma aminobutyric acid (GABA) mechanism to improve the salt tolerance of maize, this paper selects two kinds of different salt tolerant maize as test material, study on Seed Germination under Salt Stress GABA. Seedling growth, antioxidant system, nitrogen metabolism, endogenous hormone content, photosynthetic system and gene differential expression, physiological pathways to clear GABA to improve maize salt tolerance and difference induced by its surface The related gene and its relationship with the function of salt tolerance. The experiment was conducted in Northeast Agricultural University College of Agriculture Greenhouse in 2014 and 2015, selection of salt tolerant maize varieties Zhengdan 958 and salt sensitive maize varieties Dongnong 253 as tested varieties, transcriptome sequencing using Zhengdan 958 male Chang 7-2. through pre screening test, Na seed germination of Cl concentration was 100 mmol/L, seedling growth Na Cl stress concentration 150mmol/L. concentration test of GABA were 0,0.25,0.5,1 and 2 mmol/L. seed germination by solution and test set the corresponding concentration for germination medium germination test, hydroponic culture medium using 1/2 Hoagland nutrient solution, when the growth of maize seedlings to clover only when processing the seedlings. The main results are as follows: (1) the application of a certain concentration of GABA can effectively alleviate the Na Cl caused by the phenomenon of.Na germination under Cl stress, 0.5mmol/ L GABA of Zhengdan 958 and Dongnong 253 seed germination rate, germination index, vigor of storage material and transport rate than Na Cl stress treatment.0.5 mmol/L GABA high seed seed treatment is best for the mitigation of Na Cl stress on radicle length and coleoptile length inhibition effect, and Na compared to Cl stress Zhengdan 958 radicle and coleoptile length were increased by 46.76% and 49.69%; Dongnong 253 was 58.52% and 45.14%.GABA treatment could significantly improve the activity of alpha amylase, thereby promoting seed germination, one of the best 0.5 mmol/L GABA. (2) a certain concentration of GABA can relieve Na Cl stress on seedling growth inhibition that is conducive to seedling morphogenesis of.GABA plant height and leaf dry weight were higher than those in the Na Cl of the plant, the concentration of GABA was better than the other treatment effect of 0.5mmol/L GABA.GABA Na Cl to ease the stress on the treatment of Dongnong 2 53 the growth inhibition effect on Zhengdan 958.GABA can improve the Na Cl stress on root fresh and dry weight accumulation, increase the total root length, root surface, root volume and root number, average root diameter decreased. The root scan pictures shows that 0.5 mmol/L GABA facilitates the formation of root hairs, which promoted the Na Cl stress water and nutrient uptake, growth is an important guarantee of good maize seedlings. (3) to a certain concentration of GABA under salt stress in the leaves of MDA and O2 content decrease, of which 0.5mmol/L GABA is the best.Na Cl stress high superoxide dismutase (SOD), provided significant peroxide the enzyme (POD) and catalase (CAT) activity to scavenge MDA and O2 - GABA, which can further improve the activity of antioxidant enzymes, including 0.5 mmol/L GABA (4). The best effect of exogenous GABA could increase endogenous GABA content in seedling leaves and roots. In the normal growth and Na Cl stress condition, GABA could increase the content of soluble protein in leaves and roots, decreased pyruvate content will produce GABA. The feedback regulation of exogenous GABA added, making GAD activity decreased.GAD activity decreases glutamate content increased, which in turn will feedback regulation of GS, GOGAT and GDH activity, the the activity is reduced. Through making the conversion of nitrogen metabolism in the process of various substances between the stable feedback regulation, thus makes the hydrolysis of soluble protein decreased in other metabolites generated while pyruvate can be better, therefore decreased. (5) under NaCl stress, ABA content in root and leaf will be increased significantly this is conducive to improve the resistance of plants,. Because ABA is inhibition of growth hormone, and it promote the antagonism of growth hormone, so in root and leaf of IAA, decreased GA and ZR content in phenotype Look at the performance of growth decreased. The addition of exogenous GABA can improve the metabolism of plant variety, such as improving the anti oxidase system, thereby reducing the damage caused by stress, so the ABA content of GABA treated plants decreased IAA, increased GA and ZR content from phenotypically characterized by plant growth and recovery. (6) exogenous the addition of GABA can reduce the Na Cl stress on leaf damage, reduced chlorophyll decomposition, thus increasing the SPAD value, photosynthetic rate, transpiration rate and stomatal conductance. Improve plant photosynthesis will improve the utilization rate of the CO2, the intercellular CO2 concentration decreased or stable trend. (7) through the analysis of the transcriptome sequencing, expression was obtained under different salt stress induced by GABA gene, gene function by comparison, selects the differences associated with the physiological index test of gene expression. The up-regulated genes, regulation over peroxisomal biosynthesis Protein genes, regulation of auxin response factor gene regulation of LHCII chlorophyll a, B binding protein gene transcription. In down regulated expression, regulation of glutamate synthase gene regulation -3- indole aldehyde oxidase, regulation of abscisic acid responsive genes. These genes up-regulated or down regulated expression of physiology the index will cause the corresponding changes, so as to reveal the stress function and the role of GABA in the Na Cl at the molecular level.

【学位授予单位】：东北农业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S513

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