接触二氧化硫后小麦叶片中逆境乙烯的生物合成

AVG和AOA强烈抑制二氧化硫处理小麦叶片中乙烯产生和ACC合成,对MACC的形成也有一定的抑制作用。CoGl_2明显抑制乙烯产生,而ACC大量积累,MACC含量则未因ACC增加而相应增加。DNP和CCCP也抑制乙烯产生,但前者引起ACC大量积累,后者引起ACC含量下降。CHI对乙烯产生和ACC形成均显示强烈的抑制作用,同时也明显抑制MACC形成。这表明小麦叶片接触SO_2引起的逆境乙烯也是循蛋氨酸→SAM→ACC→乙烯途径。     

不同方式干旱胁迫对小麦乙烯释放、ACC和MACC含量的影响

小麦在离体气干时,C_2H_4和ACC先升后降MACC持续增加;在整体土旱条件下,乙烯不增加,ACC和MACG含量也没有明显变化。用PEG溶液进行干旱模拟实验,渗透势在-5×10~5P_a以下的一次性处理能使小麦植株的C_2H_4,ACO和MACC水平增高;逐步降低渗透势,则三者皆不增加。两种反应情况分别与离体气干和整体土旱相似,说明干旱胁迫的方式和强度的不同导致小麦植株发生不同的反应。     

镉引起小麦苗逆境乙烯的产生及其和镉的吸收分布的关系

溶液培养小麦幼苗转移至含Cd~(2 )的营养液中,根系乙烯产生较快地增加,约在12h达高峰,然后下降;ACC含量亦呈先升后降的趋势。未和Cd~(2 )溶液直接接触的地上部乙烯亦增加,至36h达高峰,此后急剧下降,而ACG和 MAGC含量持续上升。地上部乙烯的增加,主要是由通过根系运往地上部的镉直接作用的结果,不是根部合成ACG运往地上部后再产生的。电镜观察表明,地上部乙烯产生和ACC含量变化的时间进程,可以与镉进入叶细胞内的部位及其对细胞膜和细胞器的影响相联系。     

二氧化硫熏气对小麦叶片中1-氨基环丙烷-1-羧酸、1-(丙二酰氨基)环丙烷-1-羧酸含量的影响及与乙烯产生的关系

在SO_2熏气9h过程中,小麦叶片中乙烯先上升,约6h达高峰,后下降;ACC含量则随熏气时间的延长而上升。停止熏气,乙烯继续下降,ACC含量也明显降低。MACC含量从熏气3h后不断上升,脱离接触后仍继续增加。6-BA预处理对SO_2引起的乙烯和ACC上升有促进作用,但对MACC含量无明显影响。SO_2熏气提高了乙烯形成酶活性。6-BA预处理对SO_2伤害有保护作用。对逆境乙烯的产生与调节作用进行了讨论。     

钙对香蕉采后乙烯释放的抑制

本实验用CaCl_2溶液对香蕉(Musa acuminata cf. 'Dwarf Davendish')组织进行真空浸透处理,研究Ca~(2 )对香蕉采后乙烯释放、EFE活性、ACC水平以及ACC/MACC比值的影响。结果表明,Ca~(2 )处理可抑制香蕉果皮和果肉组织乙烯生成,对抑制果皮的乙烯生成尤为明显。Ca~(2 )处理还可降低内源ACC水平,抑制EFE活性。结果还显示,Ca~(2 )处理对组织中ACC/MACC比值有一定影响。     

氧和二氧化碳对莱阳梨果肉切片乙烯生物合成的调节作用

跃变期的莱阳梨果肉切片保温12h期间,降低空气中O_2浓度使乙烯生成减少,ACC含量相应增加,解除处理后,除0％O_2处理外都能恢复相应的乙烯生成速率。CO_2对乙烯生成有促进和抑制双重作用,处理初期表现出促进,O_2浓度低时更显著,随保温时间延长CO_2表现出抑制作用并继续增强。CO_2浓度增高,乙烯生成的抑制增强,ACC含量变化与乙烯减少之间没有很好的相应关系,解除CO_2处理后乙烯生成速率不能恢复。     

瓠瓜劝苗的乙烯释放与ACC,乙烯利的吸收和运转

以~14G—ACC饲喂瓠瓜幼苗基部叶片,其放射性在植株各部位呈不均匀分布,大部分集中于生长旺盛的生长点与正在形成的花芽。饲喂后4h内,ACC主要以游离形式存在,24h后,出现ACC的结合物MACC.     

表油菜素内酯对黄化绿豆下胚轴切段MACC、ACC和乙烯生成的影响

1979年Grove等从油菜花粉分离得到一种新的植物生长调节物质——油菜素内酯,它具有生长素、赤霉素类似活性,并与生长素有加合作用(Yopp等 1979,1981;Takeno和Pharis 1982)。诱导乙烯产生是生长素一个显著的生物效应;Yopp等(1979)和Arteca等(1983)分别报道过油菜素内脂对绿豆等生长素诱导乙烯增加的加合作用,促进乙烯前体1-氨基环丙烷基-1-羧酸的合成(Schlagnhaufer等1984)。本文主要研究了BR及其与IAA共同对ACC和乙烯生成的影响的特征及其对MACC形成的促进作用。     

植物组织内ACC含量测定的一些问题探讨

在许多植物组织中,乙烯生物合成的速率与组织中ACC含量密切相关,灵敏而准确地测定植物组织中ACC含量变化,对了解ACC含量对乙烯生成速率的影响十分必要。目前,测定ACC含量多数是应用LhaL和Yang［。j根据ACC可被Na0CI氧化产生乙烯的原理而提出的方法,此法的灵敏度和准确度取决于ACC转化为乙烯的效率,而ACC转化为乙烯的效率受植物样品内某些有机成分的影响,这些有机成分影响的大小与分析样品的前处理方法有密切关系。其前处理方法大致分为两类,一类是用5％横基水杨酸抽提样品中的ACC,再用阳离子交换树脂或离子交换纤维素…     

含ACC脱氨酶的根际细菌提高植物抗盐性的研究进展

盐胁迫是抑制植物生长的主要非生物因素之一,高浓度的盐分不利于植物体的生长和发育,严重时会导致植物细胞及植物体死亡.已有大量实验结果显示含ACC脱氨酶的根际细菌可以缓解高盐对植物的危害.ACC脱氨酶可以降解乙烯的直接前体1-氨基环丙烷-1-羧酸(ACC),从而降低胁迫乙烯的合成量.胁迫乙烯是阻碍植物生长的主要原因.首先介...     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.