萘乙酸对拟南芥根生长发育的影响

发布时间：2018-05-08 23:21

本文选题：拟南芥 + 主根　；参考：《郑州大学》2017年硕士论文

【摘要】：拟南芥是属于双子叶植物的一种模式植物,它的根系是由主根、侧根以及不定根组成,而其对于环境和植物激素所受的影响表现各不相同。例如高浓度生长素能促进侧根(LR)起始和形成,而抑制主根(PR)的生长。拟南芥的主根根尖可分为分生区、伸长区、成熟区、根冠等区域,分生区细胞分裂能力强,伸长区是根伸长最快的地方。生长素参与调控主根和侧根生长发育的整个过程,具有调节细胞的分裂、伸长和分化作用。为了探究生长素对拟南芥主根和侧根发育和形成的机理,因此作者使用了0.0125、0.025、0.05、0.1mg/L四种浓度生长素类似物萘乙酸(NAA)对拟南芥进行处理,分析不同处理下的拟南芥主根根长、根尖分区的变化以及侧根数目的变化,并且分别以主根长度变化和侧根数目这两方面从细胞生物学和分子生物学层次上来解释这种变化的机理。1、外源NAA处理抑制主根的伸长,而且浓度越高抑制效果越明显。本文用显微镜进行观察并测量了分生区、伸长区、成熟区长度的变化,发现分生区的长度变长,伸长区长度变短,成熟区长度基本不变。由此说明NAA抑制主根伸长,主要是抑制伸长区长度。又连续三天用Image J软件测量了伸长区细胞长度和细胞数目变化,发现细胞长度变长,而细胞数目没有变化,说明NAA促进伸长区细胞长度扩张,而没有影响其分裂能力,也就是NAA通过抑制伸长区细胞长度扩张,从而减少了伸长区长度,进而抑制了主根的伸长。生长素通过松弛细胞壁和增加细胞壁膨压来实现细胞的伸长,而这个功能是通过生长素结合蛋白ABP1来实现的,细胞内ABP1基因的水平高低与细胞的伸长密切相关。本文通过实时定量PCR研究结果表明NAA抑制了ABP1的活性,从而抑制了伸长区细胞的伸长;生长素输入载体AUX1和生长素流出载体PIN1对于细胞内生长素浓度梯度的维持起着至关重要的作用,由于NAA亲脂性,是通过自有扩散进入细胞的,因此AUX1的相对表达量没有变化,而高浓度NAA降解根中PIN1蛋白表达量,从而抑制了生长素的极性运输,进而抑制了主根的伸长。2、外源NAA的处理能增加侧根原基的密度和侧根数目,而且浓度越高这种促进作用就越强。拟南芥的侧根起始于正对着原生木质部的中柱鞘细胞,高浓度的生长素能刺激中柱鞘细胞的分裂,从而导致侧根的大量发生。而侧根的发生过程又分为四个阶段,每个阶段都受到不同的基因所调控,而外源NAA能够通过改变控制侧根发生过程中基因的相对表达量,进而促进了侧根的形成。第一个阶段即生长素信号传导过程:生长素信号分子经过生长素向内运输载体AUX1运输到中柱鞘细胞中,再经由质膜上生长素向外运输载体PIN蛋白运输到细胞外,从而在根中形成一个生长素浓度梯度,这是侧根形成的必要的条件;而PIN蛋白的含量的高低又受到P5PIK2基因的调控。外源NAA处理之后,根中的P5PIK2基因的表达量升高,进而更有利于完成生长素信号分子传导过程,形成浓度梯度。第二个阶段即侧根原基的起始过程:生长素在中柱鞘细胞形成不同的浓度梯度后,直接结合并活化运输抑制剂响应蛋白TIR1导致AUX/IAA蛋白IAA14、IAA28被泛素-蛋白酶体降解途径降解。根中IAA14的降解,使得生长素响应因子ARF7、ARF19的被活化,进而激活受它调控的下游基因LBD16和LBD29基因的转录,从而激活细胞增殖和形态基因转录;而IAA28含量的降低,解除了对生长素诱导的侧根形成基因转录的抑制作用,从而有利于侧根原基的形成。第三个阶段为侧根原基分化过程:外源NAA处理下,核蛋白ALF4的升高,促进了中柱鞘细胞的分裂和分化;而类受体酶ACR4的升高,抑制了其它邻近的非侧根原基细胞的分裂和分化。第四个阶段即为侧根突破表皮过程:外源NAA处理下,生长素输入载体LAX3表达含量的提升,促进了细胞壁分解酶的含量的升高,进而有利于细胞壁的分解和细胞的分离,使得侧根原基能层层突破外围细胞,露出表面,向外生长发育。本论文加深了外源NAA对拟南芥根系发育影响的信号途径和分子机理的理解。这些研究为外源生长素影响植物根系发育的机理的进一步的研究提供一定的参考价值。
[Abstract]:Arabidopsis is a model plant of dicotyledonous plants, whose roots are composed of the main roots, the lateral roots, and the adventitious roots, and their effects on the environment and plant hormones are different. For example, the high concentration auxin can promote the initiation and formation of the lateral root (LR) and inhibit the growth of the main root (PR). In the region of raw, elongated, mature, root and crown areas, the cell division ability of the sub region is strong and the elongation area is the fastest root elongation. The auxin participates in the whole process of regulating the growth and development of the main roots and lateral roots, which regulates the division, elongation and differentiation of the cells. Therefore, the author used 0.0125,0.025,0.05,0.1mg/L four concentrations of auxin analogue naphthacetic acid (NAA) to treat Arabidopsis thaliana, and analyzed the root length of the main root of the Arabidopsis thaliana, the change of the root apex and the number of lateral roots, and the change of the main root length and the number of the lateral roots from the two aspects of the cell biology and the molecule, respectively. The biological level explains the mechanism of this change,.1, the exogenous NAA treatment inhibits the elongation of the main root, and the higher the concentration is, the more obvious the inhibition effect. In this paper, the microscope is used to observe and measure the variation of the sub region, elongation zone and the length of the mature region. The length of the sub region is longer, the length of the elongation zone is shorter, and the length of the mature region is basically the same. This indicates that NAA inhibits the elongation of the main root and mainly inhibits the length of the elongated region. The length of cell length and the number of cells in the elongated area are measured by Image J software for three days. It is found that the length of the cells is longer and the number of cells does not change, indicating that NAA promotes the expansion of the elongated area, but does not affect its division ability, that is, the NAA through inhibition extension. The length of the cells in the long region is expanded, which reduces the length of the elongated area and inhibits the elongation of the main root. The growth of cell wall is realized by the relaxation of cell wall and the expansion of cell wall. This function is realized through the auxin binding protein ABP1, and the level of the intracellular ABP1 gene is closely related to the elongation of the cells. The results of real-time quantitative PCR study show that NAA inhibits the activity of ABP1 and inhibits the elongation of cells in the elongated region; the auxin input vector AUX1 and the auxin outflow vector PIN1 play a vital role in the maintenance of intracellular auxin concentration gradient. Because of the lipophilicity of NAA, it enters the cell by its own diffusion, so AUX1 The relative expression amount was not changed, and the high concentration of NAA degraded the expression of PIN1 protein in the root, thus inhibiting the polar transport of auxin and inhibiting the elongation of.2. The treatment of exogenous NAA could increase the density and the number of lateral roots of the lateral root, and the higher the concentration, the stronger the promotion effect. The lateral root of Arabidopsis thaliana began to face Yu Zheng. In the primary xylem sheath cells, the high concentration of auxin can stimulate the division of the central sheath cells and lead to a large number of lateral roots, and the occurrence of the lateral roots is divided into four stages, each of which is regulated by different genes, and the exogenous NAA can control the relative expression of genes during the occurrence of the lateral root. The first stage is the formation of the lateral root: the auxin signal transduction process: the auxin signal molecules are transported to the middle column sheath cells through the auxin via the endogenous transporter AUX1, and then transported to the cells via the plasma membrane of the plasmalemma to transport the carrier PIN protein to the cell, thus forming a gradient of auxin concentration in the root, which is the lateral root. The necessary conditions for the formation of the PIN protein content are regulated by the P5PIK2 gene. After exogenous NAA treatment, the expression of P5PIK2 gene in the root increases, which is more conducive to the completion of the auxin signaling molecular conduction process and the formation of the concentration gradient. The second stage is the initiation process of the lateral root primordium: auxin in the middle column sheath cells. After the formation of different concentration gradient, direct binding and activation of the transport inhibitor response protein TIR1 leads to the degradation of AUX/IAA protein IAA14, IAA28 is degraded by the ubiquitin proteasome degradation pathway. The degradation of IAA14 in the root causes the activation of the auxin response factor ARF7, ARF19, and then activates the transcription of the downstream gene LBD16 and LBD29 genes regulated by it. Activation of cell proliferation and morphogenetic gene transcription, and the decrease of IAA28 content, relieves the inhibition of the gene transcription induced by auxin induced lateral root formation, which is beneficial to the formation of lateral root primordium. The third stage is the process of lateral root primordium differentiation: exogenous NAA treatment, the increase of nuclear protein ALF4, promote the division and differentiation of the middle column sheath cells; The increase of the class receptor enzyme ACR4 inhibits the division and differentiation of other adjacent non lateral root primordium cells. The fourth stage is the breakthrough of the epidermis of the lateral root: the enhancement of the LAX3 expression content of the auxin input carrier, which promotes the increase of the content of the cell wall decomposing enzyme under exogenous NAA treatment, and is beneficial to the decomposition of cell wall and the cell division. In this paper, the signal pathway and molecular mechanism of the effect of exogenous NAA on the root development of Arabidopsis thaliana can be understood. These studies provide a certain reference value for the further research on the mechanism of the effect of exogenous auxin on the development of plant root system.

【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：Q945

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