铝胁迫对接种丛枝菌根真菌樟树幼苗光合作用的影响

在实验室条件下用低(0.5 mmol·L-1)、中(8 mmol·L-1)、高(15 mmol·L-1)浓度Al3 溶液胁迫接种和未接种丛枝菌根(AM)的樟树幼苗,10周后测定植株叶片的叶绿素含量、净光合速率(Pn),气孔导度(Gs)、蒸腾速率(Tr)、胞间CO2浓度(Ci)和气孔限制值(Ls).结果表明:未接种和接种樟树幼苗叶片叶绿素含量在低浓度Al3 胁迫时与相应对照无显著差异,而在中、高浓度Al3 胁迫下均显著低于相应对照,并均随Al3 浓度增加而逐渐下降;接种植株的叶绿素含量在对照和中、低浓度Al3 胁迫下均高于相应未接种植株,而在高浓度Al3 胁迫下显著低于未接种植株.未接种和接种樟树幼苗叶片Pn在低浓度Al3 胁迫时均显著高于对照(P<0.05),在中、高浓度时均显著低于对照,且在Al3 浓度间差异显著;末接种和接种樟树幼苗叶片Ci均随Al3 胁迫浓度增加逐渐提高,而其余参数则逐渐下降;在同一Al3 浓度处理下,接种和未接种植株的叶片光合参数均无显著差异.研究发现,中、高浓度Al3 胁迫能显著降低樟树幼苗的净光合速率,且光合机构活性降低是主要原因;接种AM真菌能显著增加中、低浓度Al3 胁迫樟树幼苗的叶片叶绿素含量,但不能显著减轻中、高浓度Al3 胁迫对樟树幼苗光合速率的抑制作用.     

NaCl胁迫对西瓜幼苗生长和光合气体交换参数的影响

以早春红玉品种为材料,采用营养液水培法,研究了不同浓度NaCl胁迫对西瓜幼苗生长、叶片光合气体交换参数、质膜透性和脯氨酸含量的影响.结果表明:25 mmol·L-1NaCl处理9 d后对西瓜幼苗生长有促进作用,>75 mmol·L-1NaCl处理则显著抑制幼苗生长;NaCl处理显著提高了叶片光合色素含量,并在100 mmol·L-1NaCl处理下达到最大;叶片净光合速率、气孔导度和蒸腾速率均随NaCl浓度提高而显著降低;胞间CO2浓度随NaCl浓度提高呈先降低后升高的趋势,在75 mmol·L-1NaCl处理下降到最小;气孔限制值随NaCl浓度提高而增加,在75 mmol·L-1NaCl处理下达到最大值后趋于稳定;水分利用率随NaCl浓度提高呈先增加后降低的趋势,在75 mmol·L-1NaCl处理下达到最大;叶片质膜透性和脯氨酸含量均随NaCl浓度提高而显著增加.结果说明:NaCl胁迫显著抑制了西瓜叶片光合作用,且低浓度处理下光合速率降低的主要原因是气孔因素限制,高浓度胁迫下则转变为非气孔因素限制.     

不同光照强度下三角叶滨藜光合作用对盐激胁迫的响应

以溶液培养的三角叶滨藜植株为材料研究了不同光照条件下其叶片光合作用对盐(NaCl)激胁迫的即刻反应及变化规律.结果表明,三角叶滨藜光合作用对盐激胁迫的响应有8 min左右的滞后期.在光照强度为100umol·m-2·-1和100 mmol·L-1浓度NaCl共同作用下,三角叶滨藜叶片净光合速率略有上升;但随NaCl浓度和光照强度进一步增加,其净光合速率呈下降趋势,且光照越强,盐胁迫导致的净光合速率下降幅度越大.同时,弱光下或强光低浓度NaCl胁迫下,盐激胁迫导致的净光合速率下降主要是气孔限制引起的;而强光下,高浓度的NaCl胁迫导致的净光合速率下降在盐激胁迫处理的前30-40 min主要由气孔限制引起.40 min后则主要由非气孔限制引起.可见,不同光照强度和NaCl浓度胁迫下三角叶滨藜叶片光合作用响应规律不同,引起净光合速率下降机制各异.     

硅对镉胁迫下红树白骨壤酚类代谢的影响

采用水培方式研究硅对重金属镉胁迫下白骨壤幼苗酚类代谢影响,探讨硅对白骨壤耐受重金属胁迫的影响,结果表明,低浓度镉胁迫(Cd 0.5 mg·L-1)下,随着外源硅的增加,叶片和根系丙二醛含量降低,但Si 50 mg·L-1处理中各器官总酚含量最高,硅对各器官单宁含量影响不显著;高浓度镉(Cd 5 mg·L-1)导致白骨壤叶片和根系膜脂过氧化,使得丙二醛含量显著高于对照,外源硅的添加显著降低了白骨壤叶片和根系丙二醛积累,Si 100mg·L-1显著增加了各器官中总酚含量和单宁含量,根系丙二醛含量与根系总酚含量呈显著负相关,叶片丙二醛含量与叶片单宁含量呈显著负相关,表明硅显著刺激高镉胁迫下白骨壤植物组织中酚类物质代谢,增加根系和叶片的抗氧化性,进而增加白骨壤对镉的耐受性。     

重金属铬(Ⅲ)对红树植物白骨壤幼苗生长的影响

采用砂基栽培,研究重金属铬(Ⅲ)不同胁迫强度(0、100、200、300、400、500、600、800 mg·L-1)和胁迫时间(25、45和150 d)条件下,对红树植物白骨壤(Avicennia marina)成熟胚轴萌发及幼苗生长的影响.结果表明:Cr(Ⅲ)胁迫(0～800 mg·L-1)对白骨壤成熟胚轴的初期萌发无明显的影响.胁迫栽培45 d时,随着Cr(Ⅲ)浓度的提高,白骨壤幼苗苗高生长、根系生长及各组分生物量和总生物量均表现出逐渐下降的趋势,但下降幅度不大.当胁迫时间延长至150 d时,Cr(Ⅲ)浓度在100 mg·L-1时对幼苗的生长影响不明显,而浓度在100 mg·L-1以上,达到200 mg·L-1以上水平,则对幼苗根系生长、苗高、叶片大小及生物量生长均具有明显抑制的作用,并将随胁迫时间的增加而加剧.     

模拟大气硫酸铵污染对香樟幼苗生长及光合特性的影响

通过室内盆栽实验研究了大气颗粒污染物硫酸铵对香樟幼苗生长及光合特性的影响。结果表明,香樟幼苗叶片涂抹硫酸铵处理对植物生长无显著影响;低浓度硫酸铵(2 g·L^-1)提高了叶片叶绿素含量,而高浓度(4 g·L^-1)却降低了叶片叶绿素含量;与对照相比,低浓度处理的香樟叶片净光合速率、气孔导度、胞间二氧化碳浓度与蒸腾速率无显著差异;高浓度处理的香樟叶片净光合速率与蒸腾速率高于对照,而气孔导度与胞间二氧化碳浓度与对照无显著差异。机理分析表明,硫酸铵颗粒物主要通过影响叶片气孔导度来影响植物光合特性。     

NaCl和Na2CO3胁迫对桑树幼苗生长和光合特性的影响

以1年生“青龙桑”幼苗为试验材料,研究了中性盐(NaCl)和碱性盐(Na2CO3)胁迫下桑树幼苗的生长和叶片光合特性.结果表明:盐胁迫明显降低了桑树幼苗的株高、叶片数、生物量和叶片的光合能力.随着Na+浓度的增加,桑树叶片的气孔导度、蒸腾速率、净光合速率、实际光化学效率、电子传递速率和光化学猝灭系数明显降低,过剩光能以非光化学猝灭形式耗散的比例增加,桑树叶片的光能转化效率和光合能力下降.在Na+浓度＜150 mmol·L-1时,桑树幼苗的光合能力和生长受到的抑制较小,通过增加根冠比进一步适应盐胁迫,但这种保护机制随着盐浓度的增加逐渐降低.在Na2CO3胁迫下,＞50 mmol·L-1 Na+浓度对桑树的生长和光合能力表现出较强的抑制作用,并随Na+浓度的增加,抑制程度加大.在NaCl＜ 150mmol·L-1时,桑树的光合能力主要依赖植株形态和光合代谢双重途径适应中性盐逆境,而在NaC1浓度＞150 mmol·L-1和碱性盐胁迫下,其主要依赖光合代谢来适应逆境.     

水杨酸对NaCl胁迫下菊芋幼苗光合作用及离子吸收的影响

为探明水杨酸(SA)对NaCl胁迫下菊芋耐盐生理的调控作用,研究了100μmol·L-1水杨酸对不同浓度NaCl胁迫下菊芋幼苗光合响应特征及离子吸收运输的影响.结果表明:施用水杨酸不仅能够有效缓解NaCl胁迫对菊芋光合作用的抑制,促进NaCl胁迫下菊芋幼苗各种光合色素含量、净光合速率、蒸腾速率、气孔导度和水分利用效率的增加,降低细胞间隙CO2浓度,同时也能明显降低NaCl胁迫下菊芋体内Na+的积累,促进菊芋幼苗对K+和Ca2+的吸收和向上运输,其中在100 mmol·L-1 NaCl处理下施用水杨酸处理的菊芋叶片中K+和Ca2+含量分别比未施用水杨酸处理增加了12.9％和14.7％,而Na+含量则降低了30.6％.由此证明,一定浓度外源水杨酸的施用有利于促进NaCl胁迫下菊芋幼苗光合功能的改善,以及有效维持菊芋幼苗体内矿质营养元素含量平衡,从而增强菊芋对NaCl胁迫的抗性,提高NaCl胁迫下的生产力.     

3种土壤类型下红椿幼苗对铅胁迫的光合响应

采用盆栽试验,研究钙质紫色土、酸性紫色土和冲积土3种土壤类型上生长的红椿幼苗在不同浓度(0、200、450、2 000mg·kg-1)铅(Pb)胁迫下的光合生理响应,探讨红椿在不同土壤类型下Pb污染的生态适应性,为木本植物的重金属修复提供理论依据。结果表明:(1)3种土壤类型下,红椿幼苗叶片叶绿素a、叶绿素b及叶绿素总量随Pb胁迫浓度的增大呈总体降低的趋势,叶绿素含量在钙质紫色土上受Pb胁迫的影响不大,而在酸性紫色土和冲积土上降低明显。(2)不同土壤类型的红椿光合响应曲线变化趋势十分相似,红椿幼苗叶片的净光合速率均随Pb胁迫程度的加大呈先增加后降低的趋势且差异显著,并在Pb浓度为200和2 000mg·kg-1时光合速率分别达到最大值和最小值。(3)随着Pb胁迫浓度的增大,红椿的最大光合速率、表观量子利用效率、光补偿点等光合生理指标都发生了显著改变,说明Pb胁迫严重影响红椿幼苗的光合作用。研究表明,高浓度的铅抑制红椿幼苗叶片叶绿素的合成,从而抑制光合作用的强度,且铅胁迫的浓度越高,叶绿素含量越低,光合作用受到的抑制越强;较低浓度的Pb处理(200和450mg·kg-1)对酸性紫色土和冲积土上红椿的净光合速率影响很小,而对钙质紫色土上红椿的最大净光合速率的抑制最为明显。     

不同形态氮素配比对盐胁迫下菊芋幼苗生理的影响

采用砂培方法研究了不同铵硝配比(NH4+/NO3-分别为4/1、1/1、1/4)的氮素营养和盐分胁迫耦合作用下菊芋幼苗的光合作用和离子吸收运输.结果表明:低浓度的盐胁迫对植物生长的抑制作用不大,而高浓度的盐胁迫却能明显抑制菊芋幼苗生物量的积累,在同一盐浓度下,提高硝态氮比例能够缓解盐胁迫对菊芋幼苗生长的抑制,促进菊芋幼苗鲜重和干重的增加;随着盐浓度的增加,菊芋幼苗地上部和地下部的Na+含量显著增加,而K+、Ca2+含量较对照显著降低,提高硝态氮比例有利于菊芋幼苗对K+和Ca2+的吸收和向上运输,从而维持地上部较高的K+/Na+和Ca2+/Na+;在3种铵硝比的氮素营养处理下,随着盐浓度的增加,菊芋幼苗叶片叶绿素含量、净光合速率、蒸腾速率、气孔导度和水分利用效率较对照均呈显著下降的趋势,细胞间隙CO2浓度则显著增加,提高硝态氮比例可显著提高盐胁迫下菊芋幼苗的叶绿素含量、净光合速率、蒸腾速率、气孔导度和水分利用效率,同时也能显著降低胞间CO2浓度,其中以铵硝比为1/4的氮素营养供应对盐胁迫的缓解作用相对较好,在100 mmol·L-1NaCl处理下其叶片叶绿素含量、净光合速率、蒸腾速率、气孔导度和水分利用效率分别是铵硝比为4/1的氮素营养处理值的1.63、1.57、1.39、1.37、1.2倍,而胞间CO2浓度则减少了17%.因此相对于铵态氮来说,硝态氮比例的增加有利于维持盐胁迫下菊芋幼苗体内矿质营养元素含量平衡,促进盐胁迫下菊芋光合功能的改善,增强菊芋对盐胁迫的抗性.     

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.