生物文獻閱讀

1、Come from： Plant Physiology and Biochemistry 59 (2012) 11-19選自 ：愛思維爾世界領先的科技與醫(yī)學出版社 植物生理學與生物化學 期刊號 59（2012）11-19Author：Farida Minibayeva*, Svetlana Dmitrieva, Anastasia Ponomareva, Victoria Ryabovol姓名：姓名：專業(yè)：專業(yè)：學號：學號： (1)自噬的兩面性 It promotes survival by degrading proteins and organelles damaged during ox

2、idative stress, but it is also activated as a part of death programs, when the damage cannot be overcome. 自噬如果能退化掉在氧化脅迫中壞死的組織以及蛋白質就能促進生存下來。但是如果損傷不能被退化掉，它也可能作為被激活的死亡部分。 （1）自噬的分階過程： Two distinct pathways exist in plants.Either autophagosomes can fuse directly with the vacuole (microautophagy) or they

3、can initially be engulfed by a smallerlysosome-like or endosome-like organelle. 自噬體可以直接和微噬體或者液泡融合。或者可以在開始的時候被像溶酶體或者核內體樣子的結構吞噬掉。 （2）相對于對酵母、哺乳動物自噬的廣泛研究，對植物自噬過程的研究還很少。 Evidence is accumulating that the cellular sites of ROS production and signaling may be primary targets of autophagy。 當時有少量證據表明已經顯示活性氧產

4、品產生位點以及發(fā)信號位點是自吞噬的首選位點。 autophagosomal targeting of ROS-producing organelles such as chloroplasts (chlorophagy), peroxisomes (pexophagy),and mitochondria (mitophagy) is of particular importance。 其中產氧氣組織有葉綠體、葉綠素、過氧化物酶體、線粒體等。 （1） Recent research efforts have shed light on the biochemical autophagic mac

5、hinery and the crucial role of several genes called (ATG)-related genes in the execution of this process. The coremachinery comprises 18 ATG proteins。 自噬往往與ATG基因有關，更進一步說是與ATG蛋白質家族有關。 （2） 主要的核心機制 PAS was known as the preautophagosoma structure PAS被成為前自噬體結構。 （3）前自噬體到自噬體的轉換過程 It expand to form autophag

6、osomes with a diameter of 500-1000 nm, and the subsequent fusion of these vesicles with lysosomal or vacuolar compartments for cargo degradation。 它能進一步擴展成為直徑為500-1000nm的結構，以及隨后的與溶酶體以及液泡的融合為了物質的降解 。 （4）植物中研究最多的是擬南芥。它類似于我們研究陽性細菌使用大腸桿菌、研究真菌使用酵母等。 The Arabidopsis genome has homologs to almost all of the

7、 yeast ATG genes. 對于擬南芥植物而言，有與酵母ATG基因相同的東西 。 In pathway， ROS function as signaling molecules to trigger autophagy . 在這個路徑中，ROS就好像促活機制一樣，作為信號分子來觸發(fā)自噬進行。 3.1 ROS-induced oxidative modifications of macromolecules ROS誘導對大分子的氧化修飾 （1）Reactive oxygen species may affect the members of signaling pathways such

8、 as protein kinases, protein phosphatases, and transcription factors。 發(fā)信號過程中可能涉及到的相關品種，比如，蛋白激酶、蛋白磷酸化酶以及轉錄因子等 （2）when plants are subjected to severe stresses ortoxic ROS inducing agents, excess ROS are generated. 當植物遭受嚴厲的脅迫或者有毒的ros誘導藥劑時，過量的ROS會產生。 （3）Other irreversible protein modifications induced b

9、y ROS include di-Tyr formation,protein-protein cross-linking, and Lys and Arg carbonylation . All these oxidative modifications can result in detrimental consequences leading to loss of cell function, and ultimately cell death. 另一種被ROS誘導的蛋白質修飾是二次酪蛋白、蛋白蛋白十字相連、賴氨酸以及精氨酸的羧基化。 所有這些氧化修飾都能導致細胞死亡或者功能缺失等后果。

10、3.2 Autophagy as an antioxidative mechanism （1） Timely isolation ，elimination and degradation of oxidized macromolecules and damaged organelles can be considered as a crucial mechanism of antioxidative defence. 及時隔離、消除和降解被氧化的大分子和損傷的細胞器可以被認為是一種重要的抗氧化防御機制。 （2）Under normal conditions, protein degradati

11、on ismediated by both the autophagic pathway and the ubiquitineproteasome system。 正常條件下，蛋白質的降解是經由自吞噬途徑和泛素介導的蛋白酶系統(tǒng)共同完成的。 Disruption of the autophagy pathway at earlier steps also leads to accumulation of ubiquitinated proteins,increased ROS and dysfunctional mitochondria. ATG18 down-regulation in Ara

12、bidopsis plants leads to the accumulation of oxidized proteins. 自噬過程的中斷也導致泛素蛋白的積累，比如ROS以及功能失效的線粒體。擬南芥下調ATG18也可能導致氧化型蛋白質的積累。 clearly, autophagy plays an important role in protecting plant cells from oxidative stresses by degrading oxidized proteins 顯然，自噬通過降解氧化性蛋白可以使植物細胞免于氧脅迫的深度影響。 Under severe stress

13、, however, the ubiquitine proteasome pathway can be over-whelmed, and the autophagic pathway is then required to increase its activity to compensate for the increased protein damage 在嚴重脅迫下，泛素介導的蛋白酶途徑可能被淹沒，自吞噬途徑不得不通過增加它的活動來彌補增加蛋白質的損傷。（3） Dysregulation of autophagy 自吞噬的異常調節(jié) It increases in oxidative s

14、tress, as shown by pharmacological inhibitor and knockout studies。 自吞噬異常調節(jié)導致氧脅迫增強。例如，藥理抑制劑，淘汰賽研究。 ATG mutants display early senescence and accelerated production of floral stems even under optimal growth conditions。 ATG 突變株可以導致早期衰老以及加速植物莖的生長，即使在最佳生長條件下。oxidative stress inwheat roots caused by prooxi

15、dants paraquat and salicylic acid results in intensive formation of autophagosomes similarly to that induced by lithium ions。 在小麥根部由百草枯或者水楊酸導致的氧脅迫誘導自噬。 Salt and osmotic stresses can also increase the production of ROS and cause damage to proteins。 鹽以及滲透壓力還可以提高ROS的產生以及對蛋白質造成損傷。 Detailed phenotypic an

16、alysis of autophagy-deficient Arabidopsis mutants revealed that autophagy may play some roles in normal developmental processes since atg mutants display early senescence and accelerated production of floral stems even under optimal growth conditions 詳細的擬南芥突變體自噬缺陷的表型分析顯示，由于突變體顯示早起衰落和，并且即使在最佳生長條件下也能加

17、速植物莖的生長，所以自噬在正常發(fā)育過程中有重要作用。 Autophagy has also been shown to transport aggregated proteins to the plant vacuole for degradation and damage to proteins during salt or osmotic stress may cause aggregation 自噬也被證明是可以將密集蛋白質運輸到降解的植物液泡，可以危害到鹽或滲透壓作用下的聚合蛋白質。 5.1 ROS generating sites in mitochondria Recent stu

18、dies indicate that plant mitochondria are at a crosspoint in the signaling pathways involving ROS, especially those concerning cell death 最近的研究表明,植物線粒體是一個包含ROS特別是有關細胞死亡的信號傳輸通道的交錯點 5.2. Oxidative modifications of macromolecules in mitochondria In normal conditions the level of O2 in mitochondria is l

19、ow,however under stress conditions when an increased demand for ATP accelerates the electron transfer via ETC, the mitochondrial membrane potential and the rates of ROS production in mitochondria are also elevated. 線粒體中正常水平下的氧氣含量很低，然而在外界壓力條件下，ATP含量會通過ETC轉化和線粒體膜電位而增加，ATP含量的增加致使線粒體中ROS產量升高。 Mitochondr

20、ial mechanisms to survive: the activation of antioxidative defence, energy-dissipating systems,and mitophagy 線粒體生存機制：激活的抗氧化防御系統(tǒng)，耗能系統(tǒng)和線狀噬菌體 6.1. Mitochondrial antioxidative systems ROS formation in mitochondria is controlled by several mechanisms including ROS-processing enzymes, non-enzymatic antiox

21、idants and uncoupling of electronflow from phosphorylation. 線粒體活性氧ROS的形成是由幾種包括活性氧處理酶、非酶抗氧化劑和磷酸化的解偶聯(lián)作用。 6.2. Energy-dissipating systems An attractive idea emerging in recent years is that AOX plays a crucial role in regulating the oxygen homeostasis within mitochondria, in particular under stress con

22、ditions, when the possibility of ROS production is increased by uncontrolled electron transfer to oxygen. 最近幾年出現了一個有吸引力的觀點，當ROS通過自由電子轉移到氧分子的產量可能增加時，特別是在外界壓力下AOX在調節(jié)氧氣和線粒體的內部平衡起著關鍵作用。 6.3. Mitophagy as a selective autophagy Accordingly, damaged, aged or malfunctioning mitochondria are a risk factor for the cell, and proper elimination of such organelles. 損傷或故障的線粒體對細胞而