UV-B辐射和NaCl胁迫对绿豆幼苗叶片DNA损伤的复合效应

研究了0·4W/m2UV-B辐射和0·4%NaCl胁迫对两绿豆品种中绿_1和秦豆-20(PhaseolusraditusL.cv.Zhongl櫣-1andQindou-20)幼苗叶片DNA损伤的复合效应。结果表明:(1)中绿-1抗UV-B辐射和NaCl胁迫的能力均强于秦豆-20;NaCl胁迫能降低中绿-1UV-B敏感性,但对秦豆-20UV-B敏感性无明显影响。(2)两逆境因子单独胁迫或复合胁迫下DNA增色效应均明显降低,但中绿-1降低程度小于秦豆-20,复合胁迫下降低程度小于单独NaCl胁迫下。(3)UV-B辐射诱导的中绿-1DNA链内环丁烷嘧啶二聚体(CPD)累积量明显低于秦豆-20;NaCl胁迫能降低UV-B诱导的中绿-1CPD累积,而对UV-B诱导的秦豆-20CPD累积无影响。(4)各种胁迫处理均导致两品种幼苗DNA含量降低,但两品种间相比中绿-1降低程度较大。结果说明UV-B辐射不仅能诱导DNA链内交联形成CPD,而且能诱导DNA链间交联和DNA含量降低,且不同绿豆品种或同一品种在有无NaCl胁迫时UV-B敏感性的差异主要与CPD累积量和DNA链间交联程度有关。     

温度对UV-B诱导的烟草叶圆片DNA损伤的影响

环丁烷嘧啶二聚体(CPD)和6-4光产物(6-4PP)是两种主要的UV-B诱导的DNA光损伤产物。利用单克隆抗体酶联免疫吸附分析法(ELISA),研究了温度对UV-B诱导的烟草叶圆片DNA损伤的影响。室温(24℃)条件下,UV-B处理引起了烟草叶圆片DNA中CPD和6-4PP的积累。0℃条件下,UV-B处理的烟草叶圆片DNA中CPD和6-4PP的积累比室温下分别降低了9.8%和12%。UV-B诱导的DNA损伤曾被认为是纯粹的光化学过程而与不受温度影响,而本实验结果表明,UV-B诱导的烟草叶圆片DNA形成CPD和6-4PP的过程具有温度依赖性。这一特性有利于植物对全球变化的适应,因而具有重要的生态学意义。     

NaCI胁迫对UV-B辐射诱导的绿豆环丁烷嘧啶二聚体和紫外吸收物质含量变化的影响

将2个对UV-B敏感性不同的绿豆品种‘秦豆-20’和‘中绿-1’幼苗放在培养室内,进行0.4W/m~2 UV-B辐射和0.4%NaCl胁迫的单独或复合处理,研究了NaCl胁迫对UV-B辐射诱导的DNA伤害和修复的影响。结果显示:在NaCl胁迫下,(1)在光下抗UV-B的品种‘中绿-1’的环丁烷嘧啶二聚体(CPD)累积量降低,而敏感品种‘秦豆-20’的CPD累积量未发生变化;(2)两品种CPD形成量均比无NaCl胁迫时低;(3)抗UV-B品种DNA的光、暗修复能力均比无NaCl胁迫时高:(4)而敏感品种DNA的光修复能力比无NaCl胁迫时低、暗修复能力未发生变化。另外,CPD形成量与紫外吸收物含量间具有明显的负相关性。说明NaCl胁迫不仅影响2个绿豆品种幼苗的CPD形成量,而且影响DNA的光、暗修复能力,进而导致了CPD累积量发生变化,由此影响了幼苗的UV-B敏感性。结果也暗示CPD形成量的变化是由于紫外吸收物质含量的不同所导致的。     

UV-B辐射对植物影响的分子水平研究进展

大气平流层中的臭氧层被破坏,导致到达地球表面太阳的UV-B辐射增强,对植物产生了多方面影响,其中包括对DNA、抗氧化酶系统、光系统Ⅱ（PSⅡ）的作用以及植物体内类黄酮等保护物质的生物合成等。UV-B辐射也是环境中重要的非生物因子,植物在长期的进化演替过程中,形成了对它的适应机制,可能被作为一种环境信号调节植物体内一系列的基因表达过程。本文论述了近些年来在分子水平上UV-B辐射对植物DNA损伤的修复、抗氧化酶和光系统Ⅱ的基因表达影响,以及有关UV-B信号传导,并对UV-B辐射的植物分子生物学研究作了展望。     

高等植物UV-B效应研究进展

本文概述了植物ＵＶ－Ｂ效应近年来的研究进展,ＵＶ－Ｂ对植物生理过程的影响表现为抑制细胞伸长,降低光合作用,引起植物细胞内活性氧代谢的紊乱,膜脂过氧化作用增强。植物种间、种内都存在ＵＶ－Ｂ敏感性差异。ＵＶ－Ｂ对植物ＤＮＡ的损伤主要是形成嘧啶二聚体。ＵＶ－Ｂ可诱导紫外吸收化合物的合成,积累,并对植物基因表达有重要调节作用。     

DNA光修复酶修复紫外损伤的DNA

DNA光修复酶在蓝光驱动下,利用黄素腺嘌呤二核苷酸（FAD）分子的黄素酶作为催化辅助因子,来修复紫外线诱导的环丁烷嘧啶二聚体（CPD）和嘧啶（6-4）嘧啶酮的DNA损伤产物。通过无根发育树,综述了DNA光修复酶/隐花色素家族的分类;详细地阐述两种DNA光修复酶的结构、光损伤后产生的嘧啶二聚体的结构及光修复过程;最后回顾了DNA光修复酶的研究现状并展望该领域的发展前景。     

DNA光解酶的结构与功能研究进展

对近年来在包括酶蛋白、辅酶的DNA光解酶结构及其与功能关系方面的研究进展作了综述.DNA光解酶可通过光诱导的电子转移催化裂解环丁烷嘧啶二聚体(Pyr<>Pyr),从而修复紫外线引起的DNA的主要损伤.研究发现,来自不同有机体的光解酶均含有两个非共价的辅基一个是1,5-二氢黄素腺嘌呤二核苷酸(FADH2),另一个是次甲基四氢叶酸(MTHF)或8-羟基-5-去氮杂核黄素(8-HDF),前者具有催化活性,可在光作用下通过电子转移裂解嘧啶二聚体,后者不具有催化活性,但能收集光子并将能量传递给FADH2,具有“天线”作用.     

单克隆抗体ELISA测定UVB诱导的DNA损伤

本文采用单克隆抗体酶联免疫吸附分析法测定了ＵＶ－Ｂ诱导ＤＮＡ产生的ＣＰＤ和６－４ＰＰ。经０．５ｍＷ／ｃｍ＾２ＵＶ－Ｂ处理１５ｍｉｎ的小牛胸物鲱鱼精ＤＮＡ,ＣＰＤ和６－４ＰＰ含量显著增加,而未经ＵＶ－Ｂ处理的对照ＤＮＡ则没有二聚体形成。     

植物UV-B生理效应的分子机制研究进展

中波紫外线UV-B（280～320nm）是植物必需的太阳光线的组成部分,具有明显的双重效应：一方面UV-B在强度较高时,就触发产生大量活性氧对DNA、蛋白质以及生物膜等造成伤害,同时植物通过抗氧化系统对其作出防御反应以减轻伤害;另一方面,低强度的UV-B是植物生长发育的光信号因子之一,经由UVR8等光受体介导中、低、极低强度的UV-B信号,可能通过几个分子途径控制相关基因的表达,分别对植物的UV-B保护基因表达、形态建成、昼夜节律、生长发育等进行调控。目前对UVR8介导的低强度UV-B信号转导的分子机制研究相对深入。在本文中,将对UV-B生理效应分子机制的最新研究进展作一个比较全面的介绍。     

单克隆抗体ELISA测定UVB诱导的DNA损伤(英文)

本文采用单克隆抗体酶联免疫吸附分析法测定了ＵＶＢ诱导ＤＮＡ产生的ＣＰＤ和６４ＰＰ。经０．５ｍＷ／ｃｍ２ＵＶＢ处理１５ｍｉｎ的小牛胸腺和鲱鱼精ＤＮＡ,ＣＰＤ和６４ＰＰ含量显著增加,而未经ＵＶＢ处理的对照ＤＮＡ则没有二聚体形成。     

Ultraviolet-B-induced DNA lesions and their removal in wheat (Triticum aestivum L.) leaves

Monoclonal antibodies were used in an enzyme-linked immunosorbent assay (ELISA) to detect the induction and removal of cyclobutane pyrimidine dimers (CPDs) and (6-4) photoproducts in DNA isolated from ultraviolet B (UV-B)-exposed primary wheat (Triticum aestivum L. cv. Chinese Spring) leaf tissue. The accumulation of lesions in the primary leaves of 6-d-old wheat seedlings was followed during the exposure of the leaf to an approximate dose of 3.6×10^?1 W m^?2 UV-B (Caldwell weighting). Significant increases in the levels of both CPDs and (6-4) photoproducts were detected in wheat leaves exposed to UV-B in the absence of other light However, only an increase in (6-4) photoproduct levels could be measured in wheat leaves exposed to the same UV-B source in the presence of supplemental white light. The removal of CPD antibody binding sites in the DNA after irradiation was rapid under conditions of high light intensity in contrast to the removal of (6-4) photoproduct antibody binding sites, which was significantly slower. The removal of CPDs appeared to be light dependent, this rate of removal decreasing with decreasing light fluences. The removal of (6-4) photoproducts also appeared light dependent, but to a lesser extent than the removal of CPDs, under the conditions studied here. Gene expression in the primary wheat leaf was measured and showed an up-regulation of chalcone synthase expression and a reduction in expression of chlorophyll a/b-binding protein (cab) in response to supplementary UV-B. No effect was seen on the expression of the other photosynthetic genes studied (the genes coding for the enzymes sedoheptu-lose 1,7-bisphosphatase and fructose 1,6-bisphosphatase). Measurement of the levels of DNA lesions in this same tissue showed that the observed changes in gene expression accompanied the appearance of UV-B induced lesions in the form of (6-4) photoproducts in the wheat leaf genome.     

Unraveling DNA Repair in Human: Molecular Mechanisms and Consequences of Repair Defect

Cellular genomes are vulnerable to an array of DNA-damaging agents, of both endogenous and environmental origin. Such damage occurs at a frequency too high to be compatible with life. As a result cell death and tissue degeneration, aging and cancer are caused. To avoid this and in order for the genome to be reproduced, these damages must be corrected efficiently by DNA repair mechanisms. Eukaryotic cells have multiple mechanisms for the repair of damaged DNA. These repair systems in humans protect the genome by repairing modified bases, DNA adducts, crosslinks and double-strand breaks. The lesions in DNA are eliminated by mechanisms such as direct reversal, base excision and nucleotide excision. The base excision repair eliminates single damaged-base residues by the action of specialized DNA glycosylases and AP endonucleases. Nucleotide excision repair excises damage within oligomers that are 25 to 32 nucleotides long. This repair utilizes many proteins to remove the major UV-induced photoproducts from DNA, as well as other types of modified nucleotides. Different DNA polymerases and ligases are utilized to complete the separate pathways. The double-strand breaks in DNA are repaired by mechanisms that involve DNA protein kinase and recombination proteins. The defect in one of the repair protein results in three rare recessive syndromes: xeroderma pigmentosum, Cockayne syndrome, and trichothiodystrophy. This review describes the biochemistry of various repair processes and summarizes the clinical features and molecular mechanisms underlying these disorders.     

Effects of Particulate Pollutants on Plants at Ultrastructural and Cellular Levels

Effects of bauxite and cement dusts on Amaranlhus dubius andPhaseolus vulgaris leaves were studied at cellular and ultrastructurallevels. Talc, an inert dust, was used as a reference material.Dusted and control leaf tissues were processed, sectioned andexamined light- and electron-microscopically. Naturally senescingleaves were also studied for comparison and understanding ofthe effects of particulates. While talc caused no alterations,both bauxite and cement induced variable cellular and ultrastructuralalterations in the dusted leaves, indicating activation of wound-repairand/or defence mechanisms and premature senescence. These alterationswere more pronounced in Phaseolus than in Amaranlhus. In addition,stress-related alterations were detected in bauxite-dusted Phaseolusleaves. Amaranlhus dubius Mart., calaloo, bauxite, cellular, cement, defence mechanisms, natural senescence, particulate, Phaseolus vulgaris L., bean, pollutant, premature senescence, stress, talc, ultrastructure, wound-repair mechanisms     

Ultraviolet photoproducts at the ochre suppressor mutation site in the glnU gene of Escherichia coli: relevance to "mutation frequency decline"

Summary Ochre suppressor mutations induced by UV in the Escherichia coli glnU tRNA gene are CG to TA transitions at the first letter of the anticodon-encoding triplet, CAA. Premutational UV photoproducts at this site have long been known to exhibit an excision repair anomaly (mutation frequency decline or MFD), whereby post-irradiation inhibition of protein synthesis enhances their excision and reduces suppressor mutation yields ten-fold. We sought to clarify the basis of this unique repair response by determining the spectrum of UV photoproducts on both strands of a 36 by region of glnU which includes the anticodon-encoding triplet. We found that four different photolesions are produced within the 3 by sequence corresponding to the tRNA anticodon: (i) on the transcribed strand, TC (6–4) photoproducts and TC cyclobutane dimers are formed in equal numbers at the site of the C to T transition, indicating that this site is a hotspot for the usually less frequent (6–4) photoproduct; (ii) on the nontranscribed strand, TT dimers are found opposite the second and third letters of the anticodon-encoding triplet, adjacent to the mutation site; and (iii) on the nontranscribed strand, an alkali-sensitive lesion other than a (6–4) photoproduct is formed, apparently at the G in the mutation site. We suggest that mutation frequency decline may reflect excision repair activity at closely spaced UV lesions on opposite strands, resulting in double-strand breaks and the death of potential mutants.     

Molecular Mechanisms of DNA Damage and Repair: Progress in Plants

Dedicated to Prof. Jan H. J. Hoeijmakers.

Referee: Dr. Nawin C. Mishra, Professor of Genetics, University of South Carolina, Department of Biological Sciences, Columbia, SC 29208

Despite stable genomes of all living organisms, they are subject to damage by chemical and physical agents in the environment (e.g., UV and ionizing radiations, chemical mutagens, fungal and bacterial toxins, etc.) and by free radicals or alkylating agents endogenously generated in metabolism. DNA is also damaged because of errors during its replication. The DNA lesions produced by these damaging agents could be altered base, missing base, mismatch base, deletion or insertion, linked pyrimidines, strand breaks, intra- and inter-strand cross-links.     

紫外线-B辐射对植物DNA及蛋白质的影响

大气平流层中的臭氧衰减,导致太阳辐射中的紫外辐射量有明显的增加,其中UV-B辐射对植物会产生不同程度的影响。分子生态学理论认为,UV-B辐射对植物造成的损伤,首先伤害植物的生物大分子,即进行光化学修饰。本文就臭氧衰减对生态环境和植物的影响途径进行了讨论,重点论述了UV-B辐射对植物蛋白质合成的抑制和DNA的损伤修复途径。并应用分子生物学技术研究植物对UV-B辐射的抗性机理和DNA修复技术的前景进行了展望。     

大豆11S球蛋白Gy5(A3B4)的基因克隆和序列分析

大豆11Ｓ球蛋白(Ｇｌｙｃｉｎｉｎ)是大豆种子的主要贮藏蛋白,分子量为360ｋＤ,由6对相同的蛋白亚基(每对亚基的分子量约60ｋＤ)构成。每对亚基又是由一个酸性Ａ肽(35～45ｋＤ)和一个碱性Ｂ肽(22ｋＤ)通过二硫键连接而成。Ａ肽和Ｂ肽源自同一个基因,即首先由一个大的ｍＲ?..     

Functional aspects of PARylation in induced and programmed DNA repair processes: Preserving genome integrity and modulating physiological events

To cope with the devastating insults constantly inflicted to their genome by intrinsic and extrinsic DNA damaging sources, cells have evolved a sophisticated network of interconnected DNA caretaking mechanisms that will detect, signal and repair the lesions. Among the underlying molecular mechanisms that regulate these events, PARylation catalyzed by Poly(ADP-ribose) polymerases (PARPs), appears as one of the earliest post-translational modification at the site of the lesion that is known to elicit recruitment and regulation of many DNA damage response proteins.