镉诱导水稻根细胞壁果胶合成及去甲酯化机制的研究

发布时间：2018-03-22 14:25

本文选题：镉　切入点：过氧化氢　出处：《浙江理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：镉(Cadmium,Cd)是一种危险的重金属,即使是低水平慢性接触都能导致高血压,脑梗塞,肺气肿,肾功能不全,癌症等多种危及生命的疾病。一般不吸烟人群摄入镉主要来自于谷物制品。水稻是镉暴露的主要谷物来源,中国有超过10%的稻米镉含量超标。目前许多研究已经证实镉胁迫使果胶含量及结构改变,但是作用机制仍不清楚。镉诱导还导致氧化胁迫产生毒害。我们在实验中发现,果胶含量与过氧化氢(H2O2)含量相关,因此推测H2O2可能与果胶合成及重构有关。研究采用水培方法,以日本晴(Oryza sativa L.,cv.Nipponbare)为材料,探究在不同镉浓度下水稻(Oryza Sativa)根系的生长及水稻根系细胞内源H2O2含量,果胶含量,果胶甲酯化酶,果胶甲酯化程度的变化,并使用H2O2清除剂4-羟基-2,2,6,6-四甲基哌啶-1-氧基(4-hydroxy-Tempo)和外源性H2O2来探索内源性H2O2的作用。此外,为了探究镉和H2O2对果胶合成的影响,对果胶甲酯酶(PME,pectin methylesterase)活性及果胶甲酯化程度(PMD,pectin methylesterification degree)也进行了研究。结果如下:1、镉胁迫明显抑制了水稻根的生长伸长,并且镉对水稻根伸长的抑制作用于镉浓度成正比,微量镉对水稻根伸长影响轻微,高浓度镉严重抑制水稻根伸长及蛋白质积累。2、在镉诱导下,水稻根内H2O2含量在短时间内急剧增加,随后果胶含量显著增加,PME活性显著增加、PMD降低。并且随着镉浓度的增加,果胶含量、PME活性增加、PMD降低。3、单独的添加外源H2O2,同样增加果胶含量和PME活性,降低PMD,结果与镉胁迫时变化趋势相同。而在镉处理的样品中添加H2O2清除剂4-hydroxy-Tempo,则抑制镉诱导下内源H2O2含量、果胶、PME活性的增加以及PMD的降低。4、其他重金属胁迫时,水稻根系细胞内源H2O2含量,果胶含量,果胶甲酯化酶,果胶甲酯化程度的变化。结果表明铝、铅和铜胁迫时也使果胶的含量和PME活性增加,PMD降低,且与镉胁迫时趋势相似。综上可知,镉诱导产生的内源性H2O2在果胶的合成、调节PME活性和果胶去甲酯化过程中起着重要作用。以前的研究大多关注果胶在植物抵御重金属毒害中的作用,然而对重金属诱导果胶合成和重构的研究没有深入。本研究则明确了镉诱导对水稻根尖细胞壁果胶含量及甲酯化程度的影响,提出并验证了内源H2O2作为关键下游信号分子参与调控镉诱导下的果胶合成增加和去甲酯化,并且H2O2作为关键下游信号分子的推论,也适用于对其他重金属的抗性调控机制。
[Abstract]:A dangerous heavy metal, even low levels of chronic exposure can lead to high blood pressure, cerebral infarction, emphysema, and renal dysfunction. Many life-threatening diseases, such as cancer. The general intake of cadmium in non-smokers comes mainly from grain products. Rice is the main source of grain for cadmium exposure. More than 10% of rice rice in China has exceeded the standard cadmium content. At present, many studies have confirmed that cadmium stress can change pectin content and structure, but the mechanism is still unclear. Cadmium inducement also leads to oxidative stress toxicity. The pectin content was correlated with the content of H _ 2O _ 2 H _ 2O _ 2.Therefore, it was speculated that H2O2 might be related to the synthesis and reconstruction of pectin. In this study, Oryza sativa L.cv. Nippon bare) was used as the material. To investigate the growth of Oryza Sativa root system and the changes of endogenous H2O2 content, pectin content, pectin methyl esterase and pectin methyl esterification degree in rice root cells under different cadmium concentrations. The effects of endogenous H2O2 on the synthesis of pectin were investigated by using H2O2 scavenger 4-hydroxy-Tempo-6-tetramethylpiperidine-1-oxy 4-hydroxy-Tempo) and exogenous H2O2, in order to investigate the effects of cadmium and H2O2 on the synthesis of pectin. The activity of PMEMEpectin methylesterase and the degree of pectin methylesterification degree were also studied. The results were as follows: 1. Cadmium stress significantly inhibited the growth and elongation of rice roots, and the inhibition of cadmium on root elongation was in direct proportion to the concentration of cadmium. Trace cadmium had a slight effect on root elongation of rice, and high concentration of cadmium seriously inhibited root elongation and protein accumulation. Under cadmium induction, H2O2 content in rice root increased sharply in a short period of time. With the increase of cadmium concentration, the PME activity of pectin increased and decreased. The addition of exogenous H _ 2O _ 2 alone also increased the content of pectin and the activity of PME. The result of decreasing PMD was the same as that of cadmium stress, but adding H2O2 scavenger 4-hydroxy-Tempoin to cadmium treated samples inhibited the content of endogenous H2O2, the increase of PME activity of pectin and the decrease of PMD in cadmium treated samples, and when other heavy metals were stressed, the contents of endogenous H2O2 and the activity of PME in pectin were increased. The changes of endogenous H2O2 content, pectin content, pectin methyl esterase and pectin methyl esterification degree in root cells of rice. The results showed that aluminum, lead and copper stress also increased pectin content and PME activity. And the trend was similar to that under cadmium stress. In summary, the endogenous H2O2 produced by cadmium was synthesized in pectin. Regulation of PME activity and pectin demethylation play an important role. Previous studies have focused on the role of pectin in the resistance of plants to heavy metal toxicity. However, the study of heavy metal induced pectin synthesis and reconstruction was not carried out. The effects of cadmium on pectin content and the degree of methyl ester formation in rice root tip cell wall were determined. It was proposed and verified that endogenous H2O2 as a key downstream signal molecule involved in the regulation of cadmium induced pectin synthesis increase and demethylation, and the inference that H2O2 was a key downstream signal molecule could also be applied to the regulation mechanism of resistance to other heavy metals.
【学位授予单位】：浙江理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S511

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