本文選題：擬南芥 + 主根��； 參考：《鄭州大學(xué)》2017年碩士論文

【摘要】：擬南芥是屬于雙子葉植物的一種模式植物,它的根系是由主根、側(cè)根以及不定根組成,而其對于環(huán)境和植物激素所受的影響表現(xiàn)各不相同。例如高濃度生長素能促進側(cè)根(LR)起始和形成,而抑制主根(PR)的生長。擬南芥的主根根尖可分為分生區(qū)、伸長區(qū)、成熟區(qū)、根冠等區(qū)域,分生區(qū)細胞分裂能力強,伸長區(qū)是根伸長最快的地方。生長素參與調(diào)控主根和側(cè)根生長發(fā)育的整個過程,具有調(diào)節(jié)細胞的分裂、伸長和分化作用。為了探究生長素對擬南芥主根和側(cè)根發(fā)育和形成的機理,因此作者使用了0.0125、0.025、0.05、0.1mg/L四種濃度生長素類似物萘乙酸(NAA)對擬南芥進行處理,分析不同處理下的擬南芥主根根長、根尖分區(qū)的變化以及側(cè)根數(shù)目的變化,并且分別以主根長度變化和側(cè)根數(shù)目這兩方面從細胞生物學(xué)和分子生物學(xué)層次上來解釋這種變化的機理。1、外源NAA處理抑制主根的伸長,而且濃度越高抑制效果越明顯。本文用顯微鏡進行觀察并測量了分生區(qū)、伸長區(qū)、成熟區(qū)長度的變化,發(fā)現(xiàn)分生區(qū)的長度變長,伸長區(qū)長度變短,成熟區(qū)長度基本不變。由此說明NAA抑制主根伸長,主要是抑制伸長區(qū)長度。又連續(xù)三天用Image J軟件測量了伸長區(qū)細胞長度和細胞數(shù)目變化,發(fā)現(xiàn)細胞長度變長,而細胞數(shù)目沒有變化,說明NAA促進伸長區(qū)細胞長度擴張,而沒有影響其分裂能力,也就是NAA通過抑制伸長區(qū)細胞長度擴張,從而減少了伸長區(qū)長度,進而抑制了主根的伸長。生長素通過松弛細胞壁和增加細胞壁膨壓來實現(xiàn)細胞的伸長,而這個功能是通過生長素結(jié)合蛋白ABP1來實現(xiàn)的,細胞內(nèi)ABP1基因的水平高低與細胞的伸長密切相關(guān)。本文通過實時定量PCR研究結(jié)果表明NAA抑制了ABP1的活性,從而抑制了伸長區(qū)細胞的伸長;生長素輸入載體AUX1和生長素流出載體PIN1對于細胞內(nèi)生長素濃度梯度的維持起著至關(guān)重要的作用,由于NAA親脂性,是通過自有擴散進入細胞的,因此AUX1的相對表達量沒有變化,而高濃度NAA降解根中PIN1蛋白表達量,從而抑制了生長素的極性運輸,進而抑制了主根的伸長。2、外源NAA的處理能增加側(cè)根原基的密度和側(cè)根數(shù)目,而且濃度越高這種促進作用就越強。擬南芥的側(cè)根起始于正對著原生木質(zhì)部的中柱鞘細胞,高濃度的生長素能刺激中柱鞘細胞的分裂,從而導(dǎo)致側(cè)根的大量發(fā)生。而側(cè)根的發(fā)生過程又分為四個階段,每個階段都受到不同的基因所調(diào)控,而外源NAA能夠通過改變控制側(cè)根發(fā)生過程中基因的相對表達量,進而促進了側(cè)根的形成。第一個階段即生長素信號傳導(dǎo)過程:生長素信號分子經(jīng)過生長素向內(nèi)運輸載體AUX1運輸?shù)街兄始毎?再經(jīng)由質(zhì)膜上生長素向外運輸載體PIN蛋白運輸?shù)郊毎?從而在根中形成一個生長素濃度梯度,這是側(cè)根形成的必要的條件;而PIN蛋白的含量的高低又受到P5PIK2基因的調(diào)控。外源NAA處理之后,根中的P5PIK2基因的表達量升高,進而更有利于完成生長素信號分子傳導(dǎo)過程,形成濃度梯度。第二個階段即側(cè)根原基的起始過程:生長素在中柱鞘細胞形成不同的濃度梯度后,直接結(jié)合并活化運輸抑制劑響應(yīng)蛋白TIR1導(dǎo)致AUX/IAA蛋白IAA14、IAA28被泛素-蛋白酶體降解途徑降解。根中IAA14的降解,使得生長素響應(yīng)因子ARF7、ARF19的被活化,進而激活受它調(diào)控的下游基因LBD16和LBD29基因的轉(zhuǎn)錄,從而激活細胞增殖和形態(tài)基因轉(zhuǎn)錄;而IAA28含量的降低,解除了對生長素誘導(dǎo)的側(cè)根形成基因轉(zhuǎn)錄的抑制作用,從而有利于側(cè)根原基的形成。第三個階段為側(cè)根原基分化過程:外源NAA處理下,核蛋白ALF4的升高,促進了中柱鞘細胞的分裂和分化;而類受體酶ACR4的升高,抑制了其它鄰近的非側(cè)根原基細胞的分裂和分化。第四個階段即為側(cè)根突破表皮過程:外源NAA處理下,生長素輸入載體LAX3表達含量的提升,促進了細胞壁分解酶的含量的升高,進而有利于細胞壁的分解和細胞的分離,使得側(cè)根原基能層層突破外圍細胞,露出表面,向外生長發(fā)育。本論文加深了外源NAA對擬南芥根系發(fā)育影響的信號途徑和分子機理的理解。這些研究為外源生長素影響植物根系發(fā)育的機理的進一步的研究提供一定的參考價值。
[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.

【學(xué)位授予單位】：鄭州大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：Q945

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