γ-氨基丁酸(GABA)对低氧胁迫下甜瓜幼苗光合作用和叶绿素荧光参数的影响

采用营养液水培方法,研究了低氧胁迫下外源γ-氨基丁酸(GABA)对甜瓜幼苗光合色素含量、光合作用及叶绿素荧光参数的影响.结果表明:低氧胁迫导致甜瓜幼苗光合色素含量显著下降,光合作用降低;外源GABA能显著提高正常通气和低氧胁迫下甜瓜幼苗的光合色素含量、净光合速率、气孔导度、胞间CO2浓度、CO2羧化效率、最大光化学效率、光化学猝灭系数、表观光合电子传递速率和PSⅡ光合电子传递量子效率,而气孔限制值、初始荧光和非光化学猝灭系数显著降低,GABA在低氧胁迫下的提高效果更明显;同时添加GABA和GABA转氨酶抑制剂γ-乙烯基-γ-氨基丁酸(VGB)处理显著降低了低氧胁迫下GABA对甜瓜幼苗光合特性的缓解效果.     

外源6-BA对低温胁迫下茄子幼苗光合作用、叶绿素荧光参数及光能分配的影响

本文研究了外源6-BA对低温胁迫下茄子幼苗光合作用、叶绿素荧光参数和能量分配的影响。结果表明,外源6．BA显著增加了低温胁迫下茄子叶绿素含量、净光合速率（Pn）、蒸腾速率（t）、气孔导度（Gs）和胞间CO2浓度（c1）;同时外源6-BA明显提高了低温胁迫下茄子幼苗叶片的PSⅡ最大光化学效率（Fv/Fm）、PSⅡ潜在活性（R／Fo）、PSII天线转化效率（FvFm）、实际光化学效率（φpsⅡ）、光化学猝灭系数（g,）和光化学反应能量（P）,降低了非光化学猝灭系数（NPQ）、天线热耗散能量（D）,对非光化学反应耗散能量（E）无明显影响。表明外源6-BA处理通过促进低温胁迫下茄子幼苗光合作用,提高光合电子传递效率,从而保护光合系统,降低低温胁迫对植物的损伤。     

外源水杨酸对黄瓜幼苗叶片PSⅡ活性和光能分配的影响

以黄瓜品种‘中农203号’幼苗为试材,采用水培法研究了根际施用0.05、0.10和0.50 mmol/L水杨酸对黄瓜幼苗叶片PSⅡ活性和光能分配的影响,以探讨水杨酸对光合作用的调节机制。结果显示:黄瓜幼苗叶片净光合速率(Pn)、荧光参数和光能分配对水杨酸的响应存在明显的浓度依赖性。0.05和0.10 mmol/L水杨酸处理提高了叶片PSⅡ最大光化学量子产量(Fv/Fm)、PSⅡ实际光化学效率(ΦPSⅡ)、PSⅡ潜在活性(Fv/F0)、电子传递速率(ETR)、光化学猝灭系数(qP),降低了非光化学猝灭系数(NPQ),使PSⅡ吸收光能中分配于光化学反应的能量增加,进而提高了Pn,并以0.10 mmol/L水杨酸施用效果最明显,差异达极显著水平(P<0.01);而0.50 mmol/L水杨酸处理降低了ΦPSⅡ、Fv/Fm等,使光能分配于热耗散和荧光耗散的比例升高,导致Pn下降。研究表明,水杨酸对黄瓜叶片光合的正负调节作用与浓度依存下的PSⅡ活性和光能分配改变有关。     

γ-氨基丁酸（GABA）对低氧胁迫下甜瓜幼苗光合作用和叶绿素荧光参数的影响

采用营养液水培方法,研究了低氧胁迫下外源γ-氨基丁酸（GABA）对甜瓜幼苗光合色素含量、光合作用及叶绿素荧光参数的影响.结果表明：低氧胁迫导致甜瓜幼苗光合色素含量显著下降,光合作用降低;外源GABA能显著提高正常通气和低氧胁迫下甜瓜幼苗的光合色素含量、净光合速率、气孔导度、胞间CO₂浓度、CO₂羧化效率、最大光化学效率、光化学猝灭系数、表观光合电子传递速率和PSⅡ光合电子传递量子效率,而气孔限制值、初始荧光和非光化学猝灭系数显著降低,GABA在低氧胁迫下的提高效果更明显;同时添加GABA和GABA转氨酶抑制剂γ-乙烯基-γ-氨基丁酸（VGB）处理显著降低了低氧胁迫下GABA对甜瓜幼苗光合特性的缓解效果.     

NaCl胁迫对马齿苋光合作用及叶绿素荧光特性的影响

以马齿苋为材料,采用温室盆栽法研究了14 d NaCl胁迫处理对其幼苗生长、光合作用和叶绿素荧光特性的影响.结果显示:(1)马齿苋幼苗的鲜重和株高在25 mmol·L-1 NaCl胁迫时与对照无显著差异,但其随着NaCl浓度的继续增加均显著降低,且其生物量受到的抑制早于株高.(2) NaCl胁迫下,马齿苋幼苗叶片净光合速率(Pn)降低,胞间二氧化碳浓度(C1)增大,且两者的变化幅度随着NaCl浓度增加而增大.(3)NaCl胁迫下,马齿苋幼苗叶片的初始荧光(F0)、最大荧光(Fm)、可变荧光(Fv)、恒态荧光(Fs)、恒态荧光与初始荧光差值(△F0)、PSⅡ潜在光化学效率(Fv/Fo)和PSⅡ最大光化学效率(Fv/Fm)均降低,叶片光化学荧光猝灭系数(qP)也在NaCl胁迫下降低,而非光化学荧光猝灭系数(NPQ)则上升;在0～50 mmol·L-1NaCl胁迫下,幼苗叶片各荧光参数下降幅度小于其他高浓度NaCl胁迫.研究表明,在NaCl胁迫条件下,马齿苋幼苗叶片的光合作用受光抑制伤害,但在低浓度NaCl下能够较多地将光能用于光化学反应,光抑制程度较低,保持了较高的净光合速率,明显减轻盐胁迫对植株生长的影响,表现出一定的耐盐性.     

外源水杨酸对镉胁迫甜瓜幼苗生长与光合气体交换和叶绿素荧光特性的影响

以甜瓜品种‘哈密绿’为试验材料,采用基质栽培方式,研究了10~200μmol·L-1外源水杨酸(SA)对镉胁迫(100mg·L-1 Cd2+)下甜瓜幼苗生长、叶绿素含量、光合气体交换参数和叶绿素荧光参数的影响,以探讨外源SA调控Cd2+胁迫伤害的可行性。结果显示:Cd2+胁迫能显著影响甜瓜幼苗的生长和相关光合指标。适宜浓度外源SA能不同程度缓解甜瓜幼苗所受Cd2+胁迫伤害,并以100μmol·L-1 SA处理效果最好,其显著促进了幼苗生长,提高了叶片叶绿素含量、净光合速率(Pn)、蒸腾速率(Tr)和气孔导度(Gs),以及PSⅡ最大光化学效率(Fv/Fm)、PSⅡ天线转化效率(Fv′/Fm′)、实际光化学效率(ФPSⅡ)、光化学荧光猝灭系数(qP)和光化学反应能量(P);显著降低了初始荧光(F0)、非光化学荧光猝灭系数(NPQ)、天线热耗散能量(D)和非光化学反应耗散能量(E)。研究表明,外源SA缓解甜瓜幼苗Cd2+胁迫伤害具有剂量效应,以100μmol·L-1 SA的效果最好,有利于甜瓜幼苗在Cd2+胁迫下光合作用的维持,提高光合电子传递效率和对光能的捕获与转换,降低Cd2+胁迫对植物的损伤,从而促进生长。     

不同浓度Ni、Cu处理对骆驼蓬光合作用和叶绿素荧光特性的影响水

以骆驼蓬幼苗为材料,采用盆栽试验研究不同浓度(0、50、100、200、400 mg·kg-1)Ni、Cu处理对骆驼蓬叶片光合作用、叶绿素荧光特性及生长状况的影响.结果表明:随着Ni浓度的增加,骆驼蓬幼苗叶片的光合色素含量、净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、PS Ⅱ最大光化学效率(Fv/Fm)、PS Ⅱ电子传递量子产率(φpsⅡ)、光化学猝灭系数(qp)及各项生长指标均呈显著下降趋势,而细胞间隙CO2浓度(Ci)和非光化学猝灭系数(qn)呈显著增加趋势,其中Pn的下降主要是由非气孔限制所致;骆驼蓬幼苗叶片的光合色素含量、Pn、Gs、Tr、Ci、Fv/Fm、φpsⅡ、qp及各项生长指标均在50 mg·kg-1Cu处理时达到峰值,叶绿素a和b、Pn、Gs、Tr、Ci、Fv/Fm及各项生长指标值在100 mg·kg-1Cu处理时仍微高于对照,而后随Cu浓度的增加,光合色素含量、Pn、Gs、Tr、Ci、Fv/Fm、φpsⅡ、qp及各项生长指标均呈下降趋势,qN呈增加趋势,其中Pn的下降主要是由气孔限制所致.     

低温胁迫下不同甘蔗品种(系)光合特性的变化及其与耐寒性的关系

以广西农科院甘蔗研究所自育的7个新材料和2个生产上的主栽品种为研究对象,在甘蔗苗期进行低温胁迫处理,研究了各品种(系)甘蔗形态特征的冷害指数、叶绿素含量及光合特性相关指标的变化及其光合特性相关指标与甘蔗抗寒性间的相关性。结果表明:随着低温胁迫处理时间的延长,冷害指数不断增大,但变化的大小与快慢因品种(系)不同表现不一样。各甘蔗品种(系)叶片叶绿素含量均随时间延长而降低。叶片净光合速率、气孔导度在低温处理与常温处理间具有显著差异。低温胁迫处理显著降低了各甘蔗品种(系)最大光化学效率(Fv/Fm)、PSⅡ实际光能转化效率ΦPSⅡ、光适应下PSⅡ反应中心的最大光能转化效率Fv′/Fm′、光化学猝灭系数qP、电子传递速率ETR,而显著提高了初始荧光Fo、稳态荧光Fs、非光化学猝灭系数qNP。相关性分析表明整个测定时期各指标间相关显著,Fv/Fm、Fv′/Fm′、ΦPSⅡ与冷害指数I之间的相关系数在0.800以上,Fv/Fm、Fv′/Fm′、ΦPSⅡ可以作为甘蔗品种(系)抗寒性鉴定的重要参考指标。     

渭北黄土区农林复合系统中大豆辣椒的光合生理特性

研究了农林复合系统不同处理对大豆、辣椒的光合特性和叶绿素荧光参数的影响.结果表明,从单作到距李子1m处,随着距李子树越近,遮光愈多.各处理大豆、辣椒的光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)表现出与光合有效辐射(PAR)基本一致的日变化模式,且与单作相比,各处理大豆、辣椒的光合速率、气孔导度和蒸腾速率均有不同程度的降低.相关性分析结果表明二者的光合速率、气孔导度及蒸腾速率均与光合有效辐射呈正相关关系.随着遮荫程度的提高,大豆、辣椒叶绿素含量和表观量子效率(Ф)升高,光饱和点(LSP)和光补偿点(LCP)降低.二者叶绿素荧光参数最大光能转换效率( Fv / Fm ) 、PSⅡ电子传递量子效率(ФPSⅡ ) 以及光化学猝灭系数( qP)均有不同程度的升高,而非光化学猝灭系数( qN P)却逐渐降低.说明大豆、辣椒能适应弱光环境,在较低的光照条件下正常生长.     

夜间低温胁迫后外源SA对恢复中黄瓜幼苗光合特性的影响

为明确低温胁迫后恢复过程中水杨酸(SA)对植物光合特性的影响,以黄瓜品种‘津研四号’幼苗为材料,通过沙培试验,研究了外源SA对夜间5℃低温胁迫后常温(25℃)恢复中黄瓜幼苗叶绿素含量、光合速率、叶绿素荧光参数、气体交换参数等的影响。结果显示:(1)与喷施清水处理相比,外源SA处理显著促进了夜间低温胁迫后的常温(25℃)恢复效果,显著提高了恢复速度和水平,表现在黄瓜幼苗叶绿素含量、净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)和胞间CO2浓度(Ci)显著升高,黄瓜幼苗净光合速率在恢复6h时达到对照水平的82.18%。(2)外源SA还明显加快了恢复过程中黄瓜幼苗叶片最大光化学效率(Fv/Fm)、实际光化学效率(ΦPSⅡ)及非循环电子传递速率(ETR)的恢复,提高了非光化学猝灭系数(NPQ)值,增强了幼苗自身光保护能力。(3)外源SA也促进了黄瓜幼苗叶片表观量子效率(AQY)和羧化效率(CE)的恢复,它们在恢复2d时分别达到对照水平的92.59%和90.62%。研究表明,在夜间低温胁迫后的常温恢复过程中,外源SA可有效地促进黄瓜幼苗光合作用的恢复,增强其对低温环境的适应能力。     

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.