高温胁迫下苋菜的叶绿素荧光特性

为了探明高温胁迫对苋菜(Amaranthus tricolor L.)光合过程的影响,用不同温度(25、30、35、40、45℃)处理苋菜植株1h后,随即测定了其叶绿素荧光动力学参数和快速光响应曲线特征参数的变化.结果表明:40℃以上高温胁迫下,苋菜叶片的光系统Ⅱ(PSⅡ)潜在光化学效率(Fv/Fo)、最大光化学效率(Fv/Fm)下降;最大荧光(Fm)、光合电子传递速率(ETR)、PSⅡ实际光化学效率(Yield)、光化学淬灭系数(qP)也均有所下降;而初始荧光(F.)和非光化学淬灭系数(NPQ)在40℃以上高温胁迫下显著上升.叶绿素荧光快速光响应曲线测定结果表明,初始斜率α、最大相对电子传递速率ETRmax和半饱和光强Ik在40℃以上高温胁迫下有所下降.研究表明,40℃以上高温胁迫对苋菜的光能的吸收、转换、光合电子传递和强光耐受能力等均有一定的影响.     

高、低温胁迫对牡丹叶片PSⅡ功能和生理特性的影响

以牡丹‘肉芙蓉’离体叶片为试材,以25 ℃为对照,研究了强光(1400 μmol·m-2·s-1)下高温(40℃)和低温(15℃)处理对牡丹叶片PSⅡ光化学活性和生理特性的影响.结果表明:随处理时间的延长,各处理叶片的PSⅡ最大光化学效率(Fv/Fm)、PSⅡ实际光量子效率(φPsⅡ)和光下开放的PSⅡ反应中心激发能捕获效率(Fv’/Fm’)均持续降低.暗恢复4h后,对照和15℃处理叶片的Fv/Fm基本上完全恢复,而40℃处理叶片仅恢复到处理前的75.5％,即使15 h后也不能完全恢复;强光下40℃处理使PSⅠ和PSⅡ间的激发能分配严重偏离平衡状态.强光下40 ℃处理抑制了超氧化物歧化酶活性,加剧了O2、H2O2、丙二醛的产生,导致叶绿素和可溶性蛋白含量不断下降.说明强光下40℃高温胁迫对牡丹叶片光合机构造成了不可逆的破坏,而15℃低温处理对其光合机构的影响相对较弱.     

高温对水稻黄叶突变体剑叶光合特性和叶绿体超微结构的影响

以水稻黄叶突变体为材料,进行高温胁迫处理(9:30～17:30,40℃;其它时间段与自然温度相同),研究高温胁迫对其剑叶光合特性和叶绿体超微结构的影响。结果表明:高温胁迫使水稻黄叶突变体剑叶净光合速率(Pn)、PSⅡ原初光化学效率(Fv/Fm)、PSⅡ光量子效率(фPSⅡ)和非循环光合电子传递速率(ETR)显著降低,初始荧光(F0)显著增加,同时使剑叶叶绿素、可溶性蛋白质含量显著降低,细胞膜透性显著增加,叶片的叶绿体内基粒和基质片层模糊、疏松,结构紊乱。研究发现,40℃高温胁迫致使水稻黄叶突变体剑叶叶绿体超微结构破坏,引起PSⅡ反应中心的光化学效率降低,最终造成叶片光合能力减弱。     

单半乳糖甘油二脂缺失对烟草光合特性的影响

以单半乳糖甘油二脂(MGDG)相对含量比野生烟草显著降低的突变体(M18)及野生型烟草为材料,通过对转基因烟草叶绿体类囊体膜的低温荧光、放氧活性以及叶片的叶绿素荧光分析,研究MGDG部分缺失对烟草叶片光合特性的影响。结果表明,在低温下(77K)MGDG部分缺失并不影响烟草叶绿素荧光发射峰(F683和F730)的位置,但使光系统Ⅱ(PSⅡ)及光系统Ⅰ(PSⅠ)的荧光发射峰的强度减弱,F683/F730比值降低,直接影响激发能在PSⅡ和PSⅠ之间的均衡分配,使叶绿素a和叶绿素b之间的能量传递受阻,降低光能转化效率;MGDG部分缺失使PSⅡ放氧活性下降了72.9%;转基因烟草叶绿素荧光参数中最大光化学效率(Fv/Fm)、暗适应最大荧光(Fm)、实际光化学效率(Yield)、光化学猝灭系数(qP)比野生型烟草分别降低了7%、49%、32%和18%,并以Fm降幅最大。研究证明,MGDG在维持植物叶绿体类囊体膜的功能,特别是PSⅡ的功能方面起着重要的作用。     

五种高速公路边坡绿化植物的生理特性及抗旱性综合评价

采用盆栽控制土壤水分,测定不同程度水分胁迫梯度下5种高速公路边坡绿化植物的叶水势、光合作用参数及叶绿素荧光参数,并以水分胁迫下各生理指标的平均变化速率为原始数据进行抗旱性综合评价。结果表明:(1)随着水分胁迫的加强,5种植物的ΨL、Pn、Tr、GS、Fv、Fm、Fv/Fm、Fv/Fo均逐渐下降,Fo逐渐升高,WUE先升后降,Ci先降后升,不同生理指标的变化幅度及拐点有一定差异;平均变化速率相对较小的是八宝景天和马蔺,较大的是肥皂草和太行菊;(2)根据水分胁迫下Gs和Ci变化方向的差异判断八宝景天、马蔺以W2作为Pn降低由气孔限制转为非气孔因素的分界线,五叶地锦、肥皂草和太行菊以W1为分界线,八宝景天、马蔺在W2时WUE最高,五叶地锦、肥皂草和太行菊在W1时最高;(3)5种植物抗旱性大小排序为:八宝景天>马蔺>五叶地锦>太行菊>肥皂草,聚类分析结果为:八宝景天、马蔺为强抗旱植物,五叶地锦为中抗旱植物,太行菊、肥皂草为弱抗旱植物。     

水杨酸对高温胁迫下黄瓜幼苗叶绿素荧光参数的影响

以津春3号黄瓜为试材,对其喷施0.05、0.1和0.5 mmol/L的水杨酸(SA)溶液,并进行了昼(40±1)℃/夜(30±1)℃高温胁迫处理,研究了黄瓜幼苗四叶期叶片叶绿素荧光参数变化.结果表明,高温胁迫下幼苗叶绿素荧光参数Fo、NPQ等显著升高,Fv/Fm、Fv′/Fm′等明显降低,嫁接苗的变化趋势弱于自根苗;不同浓度的SA溶液可缓解高温胁迫对黄瓜幼苗叶绿素荧光参数的影响,且以0.1 mmol/L的SA处理效果最优.     

三种濒危木兰植物幼树光合特性对高温的响应

以3种木兰科濒危植物香木莲、大叶木莲及大果木莲为试材,利用LI-6400便携式光合作用测量系统、叶圆片氧电极仪及叶绿素荧光仪,在夏季对其气体交换特性及叶绿素荧光参数等进行了测定.结果表明,3种木兰幼树叶片净光合速率(Pn)的日变化曲线呈双峰型,第1个峰出现在08:00,第2个峰出现在14:00～16:00,12:00有明显的光合"午休"现象.3种木兰植物的最大净光合速率(Pmax)为5.2～7.4μmolm-2s-1 ,光补偿点(LCP)为14～17 μmolm-2s-1 ,光饱和光强(LSP)为500～800μmolm-2s-1,大叶木莲的Pmax、LSP和表观量子产额(AQY)显著高于香木莲和大果木莲.随着温度升高,3种木兰植物光合放氧速率先升后降,最适温度为35℃,香木莲的放氧速率显著低于大叶木莲和大果木莲.短期高温胁迫下(45～50℃)3种木兰植物的PSⅡ最大光化学效率(Fv/Fm)均明显降低,初始荧光(F0)升高,大叶木莲的Fv/Fm降幅和F0的升幅均显著低于香木莲和大果木莲.3种木兰植物的光合速率和耐高温能力的顺序为大叶木莲＞大果木莲＞香木莲.     

营养液pH对3种藤本植物生长和叶绿素荧光的影响

以金银花、牵牛花、爬山虎3种藤本植物为材料,在不同pH营养液培养,对其株高、茎粗、植株干重、叶绿素含量、叶绿素荧光等指标进行了测定分析.结果表明:(1)随着营养液pH的升高,金银花各生长指标和叶绿素含量逐渐升高并在pH为8.2时达到最大值,爬山虎在pH为6.2时各生长指标和叶绿素含量达到最大值,牵牛花在pH从5.2变化到9.2之间,除了植物干重外,各生长指标和叶绿素含量的值变化不大.(2)随着pH的升高,金银花的PSⅡ最大光能转化效率(Fv/Fm)、PSⅡ的潜在活性(Fv/F0)、PSⅡ捕获激发能的效率(Fm/F0)及PSⅡ实际光化学效率(ΦPSⅡ)明显上升,并在pH为8.2处达到最大值;爬山虎各参数值则明显下降;牵牛花在pH为6.2处达到最大值后,随着pH的升高再无明显变化.可见,金银花更适应于喀斯特等偏碱性(pH 8.2)的环境生长.     

高温干旱胁迫对辣椒热害指标及叶绿素荧光参数Fv/Fm的影响

本试验设定38℃和5%、10%、20%的聚乙二醇6 000溶液模拟高温干旱胁迫条件,对5个辣椒种质不同胁迫时间的失水率、热害指数以及叶绿素荧光参数Fv/Fm的变化进行研究,并运用上述指标对辣椒种质进行抗性评定。实验表明,随着高温时间的延长及PEG浓度的升高,辣椒的失水率、热害指数都呈现上升的趋势,而叶绿素荧光参数Fv/Fm则为下降的趋势,但在不同胁迫时间和浓度下,各种质呈现一定的差异,其中,当38℃高温和20%PEG处理36 h时,最大失水率为71.66%(SS-Ⅱa),最大热害指数为100%(HP),而Fv/Fm降幅最高的为31.15%(黄牛),通过生理指标的隶属度分析法和叶绿素荧光参数Fv/Fm降幅的排名得出NJ2C可用于抗(耐)高温干旱胁迫育种。     

高温干旱复合胁迫及复水对构树(Broussonetia papyrifera)幼苗光合特性和叶绿素荧光参数的影响

近年来,全球气温不断升高,亚热带部分地区夏季高温和临时性干旱现象日益显著,高温与干旱严重威胁着植物的生存与生长。本文通过设置不同的温度和土壤水分梯度,研究了高温与干旱复合胁迫及复水对构树幼苗光合特性和叶绿素荧光参数的影响。结果表明:高温干旱复合胁迫下,构树幼苗净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、最大荧光(Fm)、PSII最大原初光化学量子效率(Fv/Fm)呈现下降趋势,初始荧光(F0)呈上升趋势;复合胁迫对Pn、Gs、Tr的影响具有叠加效应;胞间CO2浓度(Ci)、Gs、Fm和Fv/Fm受温度影响显著(P0.05),Gs、Tr、F0受土壤水分影响显著(P0.05),而Pn和F0受温度和土壤水分双因素影响显著(P0.05);在25和33℃下,复水对胁迫具有一定的缓解作用,复水后光合特性和Fv/Fm有一定程度提升,对F0和Fm效果不明显。试验表明,复合胁迫对植物光合特性和叶绿素荧光参数的影响程度比单一胁迫大,且在一定温度范围内,复水对干旱胁迫具有缓解作用。     

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).     

Development of a Novel Reverse Transcription Loop-Mediated Isothermal Amplification Method for Rapid Detection of SARS-CoV-2

In conclusion, the novel visual RT-LAMP assay is a simple, rapid, and sensitive approach for detection of SARS-CoV-2, and it is ready for application in primary care and community hospitals or health care centers, and even patients' own houses in response to the current SARS-CoV-2 epidemic because the assay does not require sophisticated equipment and skilled personnel. Furthermore, it is also ready to be used in fields for screening samples from wild animals and environments to facilitate the identification of potential intermediate hosts that mediate the cross-species transmission of SARS-CoV-2 from bats to humans.