外源水杨酸预处理对低温胁迫下甜瓜幼苗生长及其抗逆生理特性的影响

以甜瓜品种‘红优’幼苗为试验材料,在人工气候箱内采用基质栽培法,对其叶面喷施不同浓度(0.1、0.5、1.0、2.0 mmol·L^-1)水杨酸(SA),研究SA预处理对低温(昼12 ℃/夜6 ℃)胁迫7 d及恢复7 d后甜瓜幼苗生长、叶绿素含量、渗透调节物质含量以及抗氧化系统的影响。结果表明：(1)低温胁迫能明显抑制甜瓜幼苗的生长,外源施用不同浓度SA预处理均能缓解低温对甜瓜幼苗的伤害,并以1.0 mmol·L^-1 SA作用最明显,且显著提高了低温胁迫下甜瓜幼苗的株高、茎粗、地上鲜重和叶绿素含量。(2)适宜浓度的外源SA预处理可明显提高低温胁迫下甜瓜幼苗叶片的渗透调节物质可溶性糖、可溶性蛋白和脯氨酸的含量,增强其渗透调节作用。(3)低温胁迫下外源SA预处理能够诱导提高甜瓜幼苗叶片中超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)、抗坏血酸过氧化酶(APX)、谷胱甘肽还原酶(GR)和脱氢抗坏血酸还原酶(DHAR)的活性,增加甜瓜幼苗叶片中抗坏血酸(ASA)、谷胱甘肽(GSH)含量、ASA/DHA及GSH/GSSG,从而有效降低叶片电解质渗透率、丙二醛(MDA)和活性氧(ROS)含量。研究发现,适宜浓度的外源SA预处理,能够在低温胁迫条件下通过增加渗透调节物质的含量,诱导增强抗氧化酶活性,以及激活ASA GSH循环系统,促进甜瓜幼苗的生长,从而提高甜瓜幼苗的耐低温性能。     

低温胁迫对两种圆柏属植物亚细胞抗氧化酶活性的影响

以祁连圆柏和圆柏幼苗为材料,研究不同处理时间下低温胁迫对圆柏属植物叶片亚细胞抗氧化酶活性的影响,探讨其在圆柏属植物叶片中的亚细胞定位。结果表明：低温胁迫下,丙二醛(MDA)含量和抗氧化酶活性随时间变化均呈先升后降趋势,祁连圆柏中抗氧化酶的种类比圆柏的多且活性强,而 MDA 含量低于圆柏,表明祁连圆柏在低温胁迫下具有更广泛的适应性。此外,两种圆柏植物叶片超氧化物歧化酶(SOD)和抗坏血酸过氧化物酶(APX)定位为叶绿体＞细胞溶质＞线粒体,过氧化氢酶(CAT)定位为线粒体＞叶绿体＞细胞溶质,谷胱甘肽还原酶(GR)定位为线粒体＞细胞溶质＞叶绿体,祁连圆柏过氧化物酶(POD)定位为细胞溶质＞叶绿体＞线粒体,圆柏POD定位为细胞溶质＞线粒体＞叶绿体,且抗氧化酶SOD、APX和 GR在亚细胞中分布差异达到极显著,这说明抗氧化酶在其中一种亚细胞中发挥主要作用,为克隆亚细胞组分中的抗氧化酶基因提供了理论依据。     

外源水杨酸对低温胁迫下火龙果幼苗的形态及生理效应

为探究外源水杨酸(SA)对低温胁迫下火龙果幼苗形态及生理的影响，该研究以‘紫红龙’火龙果幼苗为材料，将4个不同浓度的SA(0.1、0.3、0.5、0.7 mmol·L^-1)喷施叶片，48 h后4℃低温培养，于第0、第3、第6、第9天观察火龙果幼苗形态及叶片组织结构的变化，并测定叶片相对电导率、丙二醛含量、渗透调节物(可溶性糖、可溶性蛋白、脯氨酸)含量及抗氧化酶(超氧化物歧化酶、过氧化物酶、过氧化氢酶、谷胱甘肽S-转移酶)活性等生理指标。结果表明：(1)低温胁迫下，火龙果幼苗呈现0级、Ⅰ级和Ⅱ级3个冷害等级，SA处理后的火龙果幼苗出现Ⅰ级冷害和Ⅱ级冷害的株数百分率均明显降低。(2)与低温对照相比，SA处理能降低火龙果幼苗叶片相对电导率和丙二醛含量并提高渗透调节物含量和抗氧化酶活性。(3)通过对不同SA处理结果进行比较分析，发现缓解冷害症状、降低相对电导率和丙二醛含量、提高可溶性糖和脯氨酸的含量、提高超氧化物歧化酶和谷胱甘肽S-转移酶的活性均以0.3 mmol·L^-1 SA效果最好，提高可溶性蛋白含量、过氧化物酶活性、过氧化氢酶活性分别以0.7、...     

24-表油菜素内酯预处理对干旱胁迫下葡萄幼苗抗氧化系统和渗透调节物质的影响

以酿酒葡萄‘雷司令’(Riesling)一年生营养袋扦插苗为材料,采用人工气候室水培试验,考察在聚乙二醇6000(PEG)模拟干旱条件下,不同浓度(0.05、0.10和0.20mg/L)24-表油菜素内酯(EBR)预处理对‘雷司令’幼苗活性氧、抗氧化物质、渗透调节物质含量和抗氧化酶活性的影响,以揭示EBR预处理对干旱胁迫下葡萄幼苗的抗旱机理。结果显示:(1)与正常生长(对照)相比,干旱胁迫显著提高葡萄幼苗叶片中超氧阴离子自由基(■)、过氧化氢(H_2O_2)和丙二醛(MDA)含量;与干旱胁迫处理(PEG)相比,不同浓度EBR预处理均可降低叶片中■、H_2O_2和MDA的含量。(2)与对照相比,PEG处理显著降低葡萄幼苗叶片的抗坏血酸(AsA)和还原型谷胱甘肽(GSH)含量;与PEG处理相比,各浓度EBR预处理均可显著提高葡萄叶片AsA与GSH的含量,且以0.10mg/LEBR处理效果最好。(3)随着干旱胁迫时间的延长,葡萄幼苗叶片中的超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)与抗坏血酸过氧化物酶(APX)活性均呈先上升后下降的变化趋势,而在正常生长条件下酶活性基本保持不变;EBR预处理的葡萄叶片SOD、CAT、POD和APX活性均始终高于同期PEG处理。(4)PEG处理条件下,渗透调节物质脯氨酸和可溶性蛋白的含量整体高于对照;与PEG处理相比,不同浓度EBR预处理在干旱胁迫中后期均能显著提高葡萄叶片中脯氨酸和可溶性蛋白含量。研究表明,在干旱胁迫下,外源EBR预处理能够提高葡萄叶片抗氧化系统酶活性和渗透调节物质含量,有效降低干旱胁迫诱导的活性氧过度积累及膜脂过氧化程度,提高葡萄幼苗的抗旱能力,且以0.10mg/L EBR处理效果最佳。     

两种圆柏属植物不同季节显微和超微结构变化与耐寒性的关系

以祁连圆柏和圆柏为材料,研究了圆柏属植物的抗寒性与解剖结构变化,以及淀粉与可溶性糖粉转化的关系.结果表明,祁连圆柏和圆柏叶片的上下表皮细胞外覆盖一层角质膜,叶肉细胞间隙大,形成发达的通气组织.在生长季节,二者叶绿体内均积累了很多淀粉粒,在冷冻休眠季节淀粉粒消失或变小,同时叶片可溶性糖分含量增加,祁连圆柏的可溶性糖分增幅高于圆柏;而休眠季节圆柏叶绿体受到低温伤害,脂质球数目增多,出现脂质小滴,部分叶绿体变形,祁连圆柏类囊体的结构受到影响较小,脂质球数量少,叶绿体形状没有发生明显的变化.因此,祁连圆柏和圆柏抗寒性与发达的通气组织和淀粉粒生长季节的积累有关,在低温胁迫下祁连圆柏叶绿体表现出高的稳定性,通过可溶性糖分的调节力强,耐寒性增强.     

盐和水分预处理对扶芳藤幼苗抗寒性的影响

测定了扶芳藤新品种‘红脉’经不同方式预处理后对幼苗抗寒性的影响,测定了膜脂过氧化水平、保护酶活性和渗透调节物质含量的变化。结果表明,与对照低温胁迫相比,0.1和0.3mol/L NaCl溶液预处理后再经低温胁迫处理,扶芳藤幼苗的膜脂过氧化水平较低、保护酶活性高、渗透调节物质含量的累积较多,不同浓度的NaCl溶液预处理比不同浓度的PEG溶液预处理对提高扶芳藤的抗寒性更有效。通过实验证明了植物在不同的逆境中确实存在着交叉适应现象,植物对各种逆境胁迫有着许多相同的生理反应,对各种胁迫的适应性存在某些共同的机制。     

叶面喷施褪黑素对低温胁迫下南瓜幼苗生长和生理特性的影响

以南瓜品种‘永安2号’幼苗为试验材料,采用室内盆栽实验,在叶面喷施不同浓度(0、50、100、150、200和300μmol·L^(-1))褪黑素(MT)后进行低温(10℃/7℃)胁迫处理,考察幼苗生长指标以及相对电导率、抗氧化酶活性、渗透调节物质含量等抗逆生理指标的变化,初步探讨外源褪黑素缓解南瓜幼苗低温冷害的生理机制。结果表明:(1)在低温胁迫条件下,南瓜幼苗出现叶片萎蔫失水、边缘失绿褪色、向内卷曲等冷害症状;幼苗株高、茎粗、鲜重、干重和壮苗指数等生长指标及叶片相对叶绿素含量均显著降低;叶片相对电导率、MDA含量和O^(-)·_(2)产生速率显著升高50%以上,超氧化物歧化酶、过氧化物酶、过氧化氢酶、抗坏血酸过氧化物酶、谷胱甘肽还原酶、脱氢抗坏血酸还原酶活性以及可溶性糖、可溶性蛋白和脯氨酸含量也大多显著升高。(2)与低温胁迫处理相比,叶面喷施不同浓度褪黑素后,南瓜幼苗叶片冷害症状均得到不同程度恢复,并以100μmol·L^(-1) MT处理生长状态最好,植株形态表型与对照已没有明显差异;幼苗生长指标以及叶片相对叶绿素含量、6种抗氧化酶活性、3种渗透调节物质含量均不同程度提高,并随着MT浓度升高均先升后降,且均在100μmol·L^(-1) MT处理最高。研究发现,外源褪黑素能通过提高叶片叶绿素含量、增强抗氧化酶活性、增加渗透调节物质积累,显著降低低温冷害造成的膜质过氧化程度,有效减轻低温胁迫对南瓜幼苗的伤害,增强其抵抗低温能力,恢复幼苗的正常生长,且喷施浓度为100μmol·L^(-1)时效果最佳。     

5-氨基乙酰丙酸对辣椒植株低温胁迫伤害的缓解效应

以‘超越五号'辣椒品种为试材,研究了低温胁迫期间及随后的常温恢复过程中5-氨基乙酰丙酸(ALA 25 mg·L-1)处理对始花期辣椒植株生长量,叶片中脯氨酸、可溶性糖、可溶性蛋白含量,超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)活性和电解质渗透率及丙二醛(MDA)含量的影响,以探讨ALA提高辣椒抗寒性的生理机制.结果表明,低温胁迫下叶面喷施25 mg·L-1的ALA可显著提高辣椒植株生长量,增加叶片中脯氨酸、可溶性糖及可溶性蛋白含量,增强其POD、CAT及APX活性,并显著降低辣椒叶片中SOD活性、电解质渗透率和MDA含量.叶面喷施ALA也显著降低了恢复过程中辣椒叶片中的渗透调节物质含量和抗氧化酶活性,使膜伤害基本恢复到对照水平.可见,外源ALA处理可通过提高低温胁迫下辣椒叶片的渗透调节能力和抗氧化能力,促进植株生长,缓解低温胁迫对植株的伤害.     

NaCl预处理提高两种铁线子属果树耐寒性的研究

古巴牛乳树和人心果是铁线子属具有开发前景的热带珍稀果树。为了将这两种果树在亚热带地区推广种植,该研究在已知这两种果树具有较高耐盐性的研究基础上,采用盆栽试验法,对3年生幼苗设置10‰、20‰的Na Cl预处理,一定时间后依次进行9℃、3℃的低温胁迫,分析比较其叶片中多种渗透调节物质含量及抗氧化酶活性的变化。结果表明:两种果树叶片渗透调节物质含量及抗氧化酶活性的变化趋势是一致的。在9℃、3℃的低温胁迫下,10‰、20‰Na Cl预处理叶片中的游离脯氨酸、可溶性糖和可溶性蛋白质含量及超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性均明显高于对照组,同一低温条件下,耐寒性强弱依次为10‰20‰对照(CK)。因此推断Na Cl预处理可以有效提高铁线子属果树的耐寒性,其中以10‰预处理最为理想,此时古巴牛乳树和人心果的实际盆土盐度分别为2.46‰、1.14‰。     

低温胁迫下棉花幼苗对外源水杨酸的生理响应

以棉花幼苗为试材,通过叶面喷施不同浓度水杨酸的处理方法,研究外源水杨酸对低温胁迫下棉花幼苗的缓解效应。结果表明,0.6~0.8 mmol＆#183;L-1水杨酸预处理可以显著降低棉花幼苗叶片相对电导率（REC）和丙二醛（MDA）的积累量,从而缓解低温对质膜的过氧化伤害,并通过提高超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）的活性和可溶性糖、可溶性蛋白、脯氨酸等渗透调节物质的含量来适应低温环境。     

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.