不同强度的UV-B辐射对高山植物麻花艽光合作用及暗呼吸的影响

以人工种植的多年生高山植物麻花艽(Uentiana straminea)为材料,在3个不同强度的UV—B辐射处理下,定时测定处理和对照叶片的净光合速率、表观量子效率和暗呼吸的变化。结果显示：UV—B处理对麻花艽叶片的光合作用在短期内有一定的抑制作用,但随着处理时间的增加,该高山植物能很快地适应强UV—B辐射的处理。表明麻花艽这种青藏高原常见的高山植物在长期的自然选择过程中可能已经形成了适应UV—B辐射的特有生理机制。暗呼吸的实验结果亦表明：在3种强度的UV—B辐射处理下,麻花艽叶片的呼吸作用从一开始就未受到抑制;随着UV—B辐射时间的增加,UV—B辐射强度越高,呼吸强度越强;这可能是UV—B辐射并未引起麻花艽呼吸机构的破坏所致。     

增强UV-B辐射对麻花艽叶片的抗氧化酶的影响

以青藏高原的特有植物麻花艽为材料,研究麻花艽叶片抗氧化酶系统对增强UV-B辐射的响应。结果表明：在UV-B处理初期,麻花艽叶片SOD、POD的酶活性都能增加,但随着处理时间的延长,SOD、POD的活性呈现下降趋势。麻花艽叶片CAT的酶活性在UVB处理后下降明显,但作为清除叶绿体中H2O2的关键酶AP的酶活性表现为明显地增加趋势,说明在对麻花艽叶片增强UV-B辐射反应中AP起有着重要作用。MDA的含量随UV-B处理时间延长而增加,表明UV-B降低了细胞内活性氧自由基的清除能力,膜脂过氧化作用加剧,导致了对麻花艽叶片的伤害效应。     

麻花艽叶片光合色素含量及厚度对UV-B辐射的响应

以中国科学院海北高寒草甸生态系统定位站自然生长的麻花艽(Gentiana straminea Maxim.)为材料,进行了不同月份和草盛期不同天数的短期增补和过滤UV-B辐射试验,比较分析叶片光合色素含量和叶片厚度等的变化.结果表明:(1)生长季内麻花艽叶片叶绿素a+b含量呈波动变化的趋势,7月份含量均较高;草盛期不同天数处理时,UV-B辐射对麻花艽叶片叶绿素a+b含量的影响不大.(2)生长季内麻花艽叶片类胡萝卜素含量也是7月份较高,短期增补UV-B辐射有降低其含量的趋势.(3)增加UV-B辐射能够降低Chl a/b值;自然UV-B辐射下Car/Chl比值能维持一个较高水平,是对强辐射的适应.(4)随处理时间延长,麻花艽叶片厚度有降低趋势,其叶缘出现一些发黄、变黑、变透明等受害症状,叶片能通过增加叶片厚度来适应增强的UV-B辐射.可见,生长于高海拔地区的植物麻花艽虽然对UV-B辐射表现出诸多的生理适应特性,但依然不可避免地受到其损伤.     

西宁和海北麻花艽净光合速率和叶绿素荧光参数的日变化比较

以青藏高原药用植物麻花艽为材料,研究了西宁和海北两个地区麻花艽叶片的净光合速率和叶绿素荧光参数的日变化进程。结果表明：在中午太阳辐射较强时两地麻花艽叶片的净光合速率（Pn）均下降,下午随日间光强的减弱逐渐上升,形成双峰曲线;海北麻花艽叶片的净光合速率（Pn）及其日变幅均低于西宁。随日间光强的增加麻花艽叶片的PSⅡ最大光化学效率（Fv／Fm）、PSⅡ的潜在活性（Fv/Fo）下降,非光化学猝灭系数（NPQ）则上升,黄昏各参数都恢复到接近早晨的水平,表明未发生光合机构的破坏;一天中海北麻花艽叶片的Pn、Fv／Fm、Fv／Fo均低于西宁,表明随海拔的升高、光强的增加,海北麻花艽热耗散增多,午间光抑制加重。     

高寒草甸麻花艽和美丽风毛菊的光合速率午间降低现象

在中国科学院海北高寒草甸生态系统定位研究站地区,用便携式光合蒸腾测定仪（CI－301PS）和液相极谱氧电极（SP－2）观测到,全晴天2种高山植物麻花艽和美丽风毛菊叶片的净光合速率（Pn),光合放氧速率和表观量子效率（AQY）有明显的午间降低现象,遮光实验表明,这种现象是由高原地区当地太阳正午时前后较强的太阳辐射造成的。     

芒果老叶在增强UV-B辐射处理下的损伤和保护反应

以‘台衣一号’芒果盆栽苗离体老叶为试材,研究增强UV—B辐射条件下芒果老叶的损伤和保护反应。结果表明：UV—B辐射处理使芒果叶片MDA含量和相对电导率升高、叶绿素含量和叶绿素a／b降低,表明叶片受到损伤,且随处理时间延长叶片损伤加重。UV—B辐射处理叶片可溶性蛋白含量、抗氧化酶（SOD、CAT、POD）活性、保护色素（类胡萝卜素、类黄酮）和还原型GSH含量显著高于对照叶片,UV—B辐射处理叶片维生素C含量显著低于对照叶片,表明增强UV—B辐射可诱导叶片细胞通过提高活性氧清除能力和积累保护色素而直接吸收部分UV—B辐射来提高抗增强UV—B辐射损伤的能力。     

自然条件下滤减UV-B辐射对烤烟光合色素含量的影响

在自然环境中,以烟草栽培品种K326为材料,通过覆盖不同透明薄膜滤减UV—B辐射,研究100％（CK）、75％（T1）、50％（T2）、35％（T3）UV—B辐射透过率处理下,不同强度UV—B辐射对烟草光合色素含量的影响。结果表明：烤烟三类光合色素对UV—B辐射有不同响应。类胡萝卜素对UV—B辐射响应较敏感。成熟初期,类胡萝卜素含量与UV—B辐射强度变化具有较好的正相关性,而chl a和chl b含量基本与UV—B辐射强度呈反向变化关系。成熟后期,由于UV—B辐射累积效应,光合色素含量变化没有明显规律。现蕾期至成熟采烤烟初期,chl a：chl b与UV—B辐射的反向变化关系较明显,后期则无明显规律,其含量的下降与UV—B辐射的累积效应有关。     

高寒草甸麻花艽和美丽风毛菊的光合速率午间降低现象

在中国科学院海北高寒草甸生态系统定位研究站地区,用便携式光合蒸腾测定仪(CI-301PS)和液相极谱氧电极(SP-2)观测到,全晴天2种高山植物麻花艽和美丽风毛菊叶片的净光合速率(Pn)、光合放氧速率和表观量子效率(AQY)有明显的午间降低现象.遮光实验表明,这种现象是由高原地区当地太阳正午时前后较强的太阳辐射造成的.     

氮素对高大气CO_2浓度下小麦叶片光合作用的影响

通过测定小麦拔节期叶片的光合气体交换参数和光强-光合速率(Pn)响应曲线,研究了氮素对长期高大气CO2浓度(760μmol.mol-1)下小麦叶片光合作用的影响.结果表明:在长期高大气CO2浓度下,增施氮肥能提高小麦叶片Pn、蒸腾速率(Tr)和瞬时水分利用效率(WUEi);与正常大气CO2浓度相比,高大气CO2浓度下小麦叶片的Pn和WUEi增加,气孔导度(Gs)和胞间CO2浓度(Ci)降低.随光合有效辐射的增强,高大气CO2浓度下小麦叶片的Pn和WUEi均高于正常大气CO2浓度处理,Gs则较低,而Ci和Tr无显著变化.高氮水平下小麦叶片Gs与Pn、Tr、WUEi呈线性正相关,Gs与Ci在正常大气CO2浓度下呈线性负相关,但高大气CO2浓度下二者无相关性;低氮水平下小麦叶片的Gs与Pn、WUEi无相关性,而与Ci和Tr呈线性正相关,表明高大气CO2浓度下低氮水平的小麦叶片Pn由非气孔因素限制.     

UV-B辐射对香蕉光合作用和不同氮源利用的影响

生长在NO3^--N、NH4^--N和NH4NO3－N的香蕉叶片有相近似的最大光合速率,UV－B辐射引起生长在不同氮源的香蕉叶片光合速率、表现量子产率和光肥利用效率的降低。UV－B辐射使生长在不同氮源的植株叶面积干重和叶氮含是降低。生长在NH4^--N的植株Vcmax和Jmax均较生长在其它氮源的高。UV－B辐射引起生长在NH4^-N的植株Vcmax和Jmax降低较相同处理的NO3^-－N和NH4NO3－N植株明显,表明生长在NH4^ －N的香蕉对UV－B辐射更加敏感。UV－B辐射改变植株的叶片的碳氢比和碳氮比。经过UV－B辐射处理的NH4^ －N生长植株的碳氮生长在NO3^--N和NH4NO3－N的低。UV－B辐射可能改变植株对不同氮源的吸收利用,从而引起碳氮代谢和酸碱调节的变化。UV－B辐射降低叶氮在Rubisco和生物力能学组分的分配系数,可能使这些组分合成减少,使叶片光调节的变化。UV－B辐射降低叶氮在Rubisco和生物力能学组分的分配系数,可能使这些组分合成减少,使叶片光合速率下降。结果表明,生长在不同氮源的香蕉植树对UV－B辐射有不同响应,NH4^ -N有利于主要光合参数增高,但其对UV－B辐射亦最为敏感。氮供应受限制或植株生长在中性盐如NH4NO3－N则对UV－B辐射不甚敏感。     

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.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Enterovirus 71 3C proteolytically processes the histone H3 N-terminal tail during infection

Highlights
1. The N-terminal tail of histone H3 is specifically cleaved during EV71 infection.
2. Viral protease 3C is identified as a protease responsible for proteolytically processing the N-terminal H3 tail.
3. Our finding reveals a new epigenetic regulatory mechanism for Enterovirus 71 in virus-host interactions.     

Detection of EBV and HHV6 in the Brain Tissue of Patients with Rasmussen’s Encephalitis

Rasmussen’s encephalitis (RE) is a rare pediatric neurological disorder, and the exact etiology is not clear. Viral infection may be involved in the pathogenesis of RE, but conflicting results have reported. In this study, we evaluated the expression of both Epstein-Barr virus (EBV) and human herpes virus (HHV) 6 antigens in brain sections from 30 patients with RE and 16 control individuals by immunohistochemistry. In the RE group, EBV and HHV6 antigens were detected in 56.7% (17/30) and 50% (15/30) of individuals, respectively. In contrast, no detectable EBV and HHV6 antigen expression was found in brain tissues of the control group. The co-expression of EBV and HHV6 was detected in 20.0% (6/30) of individuals. In particular, a 4-year-old boy had a typical clinical course, including a medical history of viral encephalitis, intractable epilepsy, and hemispheric atrophy. The co-expression of EBV and HHV6 was detected in neurons and astrocytes in the brain tissue, accompanied by a high frequency of CD8⁺ T cells. Our results suggest that EBV and HHV6 infection and the activation of CD8⁺ T cells are involved in the pathogenesis of RE.     

Perinatal Vertical Transmission of Chikungunya Virus in Ruili,a Town on the Border between China and Myanmar

正Dear Editor,Chikungunya virus (CHIKV), an arbovirus in the family of Togaviridae, genus Alphavirus, is transmitted by the A.aegyptii or A. albopictus mosquito, and causes disease in humans characterized by fever, rash, and arthralgia (Silva and Dermody 2017; Suhrbier 2019). It was first reported in 1953 in Tanzania, and caused only a few outbreaks and sporadic cases in Africa and Asia in last century. However, in the epidemic in 2004, CHIKV acquired mutations that conferred enhanced transmission by the A. albopictus mosquito(Schuffenecker et al. 2006). Since then, it has successively caused outbreaks in Africa, the Indian Ocean, South East Asia, the South America, and Europe (Zeller et al. 2016).