水稻幼叶中与ABA亲和力强的结合蛋白

在水稻幼苗叶片中存在膜结合的 ABA 专一结合位点。专一结合位点对 ABA 具有强的亲和力,其与 ABA 反应的平衡解离常数为2.69×10~(-7)mol/L,总浓度为4 nmol mg~(-1)蛋白质。专一结合位点与 ABA 结合活力在0℃时比25℃时高115%。专一结合位点与 ABA 结合的最适 pH 为4.5。ABA 与其专一结合位点的结合量随反应时间延长而增加,1小时达最大值,以后又逐渐降低。这种降低可能是由于专一结合使点活性逐渐减弱所致。这类结合位点可能是 ABA 进入细胞的载体,也可能是 ABA 作用的受体。     

棉花叶片衰老过程中激素和膜脂过氧化的关系

以陆地棉品种辽棉9号的去根幼苗为材料,对其进行暗诱导衰老培养.在培养液中分别加入6-BA、ABA、GSH、H2O2、CaCl2、A23187 和A23187 CaCl2,测定在不同培养条件下棉花去根幼苗叶片内源激素、SOD酶活性和MDA含量的变化.结果表明:棉花叶片衰老表现为细胞分裂素含量的下降和ABA含量的上升.6-BA、GSH和钙离子均延缓叶片的衰老,ABA和H2O2促进叶片的衰老.     

苹果果实细胞质中依赖活体组织的ABA高亲和力特异结合蛋白

将苹果（Malus pumila L.cv.Starkrimon)果肉微粒体和细胞可溶组分在含有^3H-ABA的缓冲介质中分别温育,仅在细胞可溶组分中测到微弱的^3H-ABA结合活性。但是,如何将果肉组织圆片在^3H-ABA缓冲介质中直接温育,经制备亚细胞组分后直接测定,在细胞可溶组分中测到很高的^3H-ABA特异结合活性。果肉圆片用沸水预先热处理使细胞可溶组分中的^3H-ABA结合活性完全丧失,说明ABA结合依赖于组织的活体状态。药理实验证明了ABA结合位点的蛋白质性质,同时证明该蛋白的活性中心具有－SH和丝氨酸基因。ABA结合蛋白对ABA的结合具有可饱和性、可逆性和高亲和力。Scatchard作图证明存在2种ABA结合蛋白,一种具有较高的亲和力,其解离常数（Kd)为2.9mmol/L,另一种亲和力相对较低,其Kd值为71.4nmol/L。用ABA结构相似物进行的竞争实验证明了ABA结合蛋白对配体结合的立体特异性。分析了ABA结合蛋白与ABA结合的时间曲线、pH和温度依赖性。本研究检测到的依赖活体组织的ABA结合蛋白可能是果实发育过程中介导ABA信号的受体。     

6-BA和ABA缓解棉纤维发育低温胁迫的生理机制

以科棉1号棉花品种为材料,于2006、2007年在江苏南京(长江流域下游棉区)设置播期(4月25日、5月25日)和生长调节剂(6-BA、ABA)试验,研究低温条件下,外施6-BA、ABA对棉铃及棉纤维发育的影响及其生理机制.结果表明:常温和低温条件下,6-BA处理均能使相应部位棉铃铃质量增加、纤维品质提高;ABA处理在常温条件下会导致品质下降,而在低温逆境条件下可使纤维品质下降幅度减小;6-BA显著提高了棉铃蔗糖含量及蔗糖合成酶、蔗糖磷酸合成酶活性,而ABA则可诱导β-1,3-葡聚糖酶活性;6-BA、ABA对纤维发育关键酶蔗糖转化酶活性的作用效果均不显著.低温条件下外施6-BA、ABA均可提高棉纤维品质,但两者作用机制不尽相同:6-BA主要通过提高纤维素合成相关酶的活性,而ABA则主要通过诱导棉株抗逆性来提高纤维品质.     

伤流液中玉米素的高效液相色谱测定

在植物体内,天然存在的细胞分裂素(Cytokinin)主要是玉米素和与玉米素化学结构相似的化合物6-(r.r-二甲基烯丙基氨基)—嘌呤。尤以玉米素活性最强,含量最多。其活性大约是细胞分裂     

小麦叶绿体中CTK结合蛋白的结合活性研究

叶绿体中存在着与细胞分裂素(CTK)专一结合的蛋白质。这一蛋白与6-苄氨基嘌呤(6 BA)的亲和力很强,解离常数达3.7×10~(-8)mol/L。最大结合量为10.7 pmol 6 BA/mg蛋白,Seatchard分析表明只有一类结合位点。不同的叶绿体纯化步骤对CTK结合蛋白的活性有不同的影响,分离步骤少而快速的差速离心法可以得到具有较高结合活性的叶绿体。叶绿体经分离纯化后,低温保存时的结合活性较稳定,-20℃以下可以较长期保存。用EDTA预处理叶绿体,不降低CTK结合蛋白对6 BA的结合活性,而用高浓度的NaCl处理,可以使叶绿体结合6BA的能力明显下降。这说明EDTA不能使CTK结合蛋白从叶绿体膜系统表面解离,而高浓度NaCl则有这种可能性。     

细胞分裂素对渍水小麦衰老的影响

与土壤渍水同时向小麦地上部喷洒细胞分裂素类物质显著减轻了渍害,表现为叶绿素的降解及类脂过氧化产物丙二醛的积累均减慢。不同种类的细胞分裂素类物质减轻渍害的活性大小次序为:6-苄氨基嘌呤(6-BA)>玉米素>6-呋喃氨基嘌呤,无生理活性的嘌呤类衍生物6-甲基嘌呤则没有减轻渍害的作用。地上部喷施IAA和GA_3不能延缓因渍水引起的衰老加速,ABA处理则有加重渍害趋势。 比较了经6-BA处理与不处理的植株在渍水时的乙烯产生和衰老出现的时间进程。未经6-BA处理的植株受渍3天时叶绿素含量明显下降,渍水诱导乙烯产生显著增加,约4天达到高峰。6-BA处理使植株叶绿素含量至少在受渍后5天内没有下降,而乙烯产生量大大地增加,高峰期同样也在受渍后4天。说明渍水引起乙烯增生和衰老加速是受渍小麦体内独立进行的两个过程,乙烯是衰老加速的促进剂,而不是触发这一过程的“板机”。 6-BA处理增加小麦幼苗乙烯产生是由于它提高了体内乙烯生物合成前体卜氨基环丙烷-1-羧酸的含量。     

拟南芥中4种细胞分裂素的高效液相色谱法测定

应用高效液相色谱法同时测定拟南芥中4种细胞分裂素组分玉米素(Z)、玉米素核苷(ZR)、6-r,r-二甲基烯丙基氨基嘌呤(2ip)和6-r,r-二甲基烯丙基氨基嘌呤核苷(2ipr)含量。结果表明,采用反相色谱柱Waters C₁₈柱(4.6×250 mm,5 μm),在35℃以乙腈和三乙胺缓冲液为流动相梯度洗脱,流速1 ml/min,在270 nm处能准确检测出拟南芥中4种细胞分裂素组分的含量,检测限达0.001 μg/ml。     

拟南芥ABA不敏感型突变体及其ABA结合特性

拟南芥的脱落醚（ABA）不敏感型突变体abi2,在对ABA的敏感性、气孔开度及种子休眠方面,与野生型有明显差异。通过3H－ABA与野生型对的亚细胞组分的结合分析,表明38000×g组分特异结合活性最高,结合最适温度为20℃,最适保温时间：20℃时为70min;0℃时为90min。由饱和曲线的Scatchard分析表明：abi2存在一种ABA结合位点,野生型有两种ABA结合位点。对3H－ABA结合的38000×g组分的SDS－PAGE电泳分析表明：野生型有3个结合活性峰,而abi2只有1个结合活性峰。     

6-BA拮抗脱落酸缓解渗透胁迫对种子萌发的抑制

细胞分裂素促进细胞分裂、芽的分化,拮抗脱落酸抑制的种子萌发,而细胞分裂素合成基因Ipt84在种子萌发过程中发挥重要的作用。本文分别用120mmol·L-1 NaCl和240mmol·L-1 甘露醇模拟盐和干旱胁迫处理拟南芥种子,探讨6一BA拮抗ABA对其抑制种子萌发和萌发后生长的影响。结果表明,细胞分裂素合成相关突变体ipt6-1、ipt6-2、ipt8．1和ipt8-2的种子萌发和生长可被NaCl和甘露醇显著抑制;而ABA合成相关突变体aba2-1对相同浓度NaCl和甘露醇的处理表现相对不敏感。进一步研究发现添加外源6一BA可恢复ipt6-1、ipt6-2、ipt8-1和ipt8—2的相关敏感表型,并且随6-BA浓度的增加,恢复效果也愈趋明显。     

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.     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

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.