甜瓜抗霜霉病基因同源序列克隆与分析

采用RT—PCR扩增的方法,从高抗霜霉病甜瓜品种‘日本安农二号’中克隆到约3kb的cDNA片段（命名为MRGH-D,该基因是一个连续的通读编码框,编码1007个氨基酸。推测的蛋白质分子量为113．7kDa,等电点为7．88,蛋白质预测无跨膜区。根据推测的氨基酸序列,该基因属于TIR—NBS—LRR类抗病基因,具有TIR-NBS—LRR类抗病基因所有的保守结构域。核苷酸序列和氨基酸序列同源性分析结果显示,MRGH-J与甜瓜抗病基因的同源序列MRGHl2及抗霜霉病相关基因mp-19均具有高达99％的同源性,推测该基因可能在甜瓜抗霜霉病中起作用。     

单核苷酸多态性与甜瓜抗枯萎病分子育种研究

目的:结合单核苷酸多态性标记技术,利用甜瓜本身的抗病性以解决新疆甜瓜病害问题。方法:对新疆甜瓜抗枯萎病基因Fom-2基因进行克隆分析,并根据Fom-2基因在不同抗性甜瓜亲本的单核苷酸多态性,设计检测SNP标记的PCR扩增引物,验证其多态性;并利用F2代分析该标记与筛选获得的甜瓜抗枯萎病基因连锁的SSR标记的遗传关系。结果:在抗病与感病甜瓜品种中均扩增获得PCR条带,试验中设计单核苷酸多态性分子标记在抗病品种为显性,与筛选的和抗枯萎病基因紧密连锁的共显性标记SSR430共分离。结论:不同抗性甜瓜品种均含有Fom-2基因或其高度同源序列,SNP显性标记和共显性标记SSR430均可用于甜瓜抗枯萎病分子标记辅助育种。     

新疆甜瓜Fom-2基因同源序列的克隆及分析

近年来甜瓜枯萎病蔓延迅速,危害严重,分离克隆甜瓜抗病基因,利用转基因技术改良甜瓜抗病品性是一种从根本上解决甜瓜枯萎病危害的新途径。根据已知Fom-2基因序列设计特异引物,采用RT-PCR技术从新疆甜瓜抗病性品种黄旦子中扩增出580bp的cDNA片段,序列分析表明它与已发表Fom-2基因具有高度同源性基因片段,命名为X-Fom-2。以X-Fom-2为探针对新疆甜瓜黄旦子、伽什瓜、红心脆、金丽-2号进行Southem blot和Northem blot,结果表明,X-Fom-2以多拷贝形式存在。X-Fom-2在抗病品种黄旦子、金丽2号有表达且在病原菌诱导后增强,而在感病品种伽什瓜、红心脆中没有表达。     

小麦抗赤霉病品种NBS同源序列克隆与分析

根据二穗短柄草NBS-LRR类基因的保守序列设计同源引物,以小麦抗赤霉病品种苏麦3号、宁7840和望水白基因组DNA为模板,通过PCR扩增,得到43条序列,其中4条为非编码序列或结构域不完整;39条与植物抗病基因同源,其中的7条内部存在终止密码子,可能是假基因,经过比对分析,其余32条具有连续的开放阅读框和保守结构域,推导的氨基酸序列均具有Kinase-1a、Kinase-2和Kinase-3a及GLPL区等几个保守区,在GenBank中均能找到与之高度同源的其他物种的核酸序列,并且Kinase-2的最后一个氨基酸均为色氨酸(W),属于non-TIR类NBS基因。32条序列可分为4大类,它们之间核苷酸同源性为64%-98%,编码氨基酸同源性为22%-98%。根据序列分析随机设计5对不同基因特异性引物,并利用RT-PCR技术进行表达分析,结果表明,7-1、s-3、s-4和w-2均能表达,说明这些片段可能是功能性抗病基因的部分序列;7-13不表达,再次证明属于假基因。32条序列在之前未被报道过,这些RGA可以作为筛选赤霉病功能性抗病基因的候选序列。     

香蕉抗病种质NBS类RGAs的克隆及相关序列差异分析

根据植物NBS类抗病基因保守氨基酸序列P-loop和疏水氨基酸GLPL保守序列设计简并引物,从香蕉抗镰刀菌枯萎病(4号小种)材料GCTCV-119的基因组DNA及cDNA中扩增获得9个DNA片段和10条cDNA片段,均编码为通读的氨基酸序列,命名为"BR-1"-"BR-19",GenBank登录号依次为EF515833-EF515836, EU123871-EU123885。同源性分析表明,均与已报道的植物抗病基因有不同程度的同源性,具有P-loop(Kinase-1a)、Kinase-2、RNBS-B(Kinase-3a)以及GLPL等保守氨基酸序列,属于non-TIR-NBS类候选抗病基因。其中,BR-5和BR-6与番茄抗镰刀菌枯萎病番茄专化型I2、I2-1和I2-2基因聚为一类,可能与香蕉镰刀菌枯萎病的抗性相关。     

3种外源诱导剂预处理对甜瓜抗病特征及其Fom 2和CHT基因表达的影响

该研究选用水杨酸(SA)、茉莉酸甲酯(MeJA)、Ca~(2+)、无菌水(对照)作为外源预处理诱导剂,以抗、感枯萎病甜瓜品种为材料,分别于诱导预处理2d后接种甜瓜枯萎菌,并于接种5、7、9d时观察发病情况,进行病情调查;在接种后1、3、5、7、9d取甜瓜叶片,分析抗病甜瓜(MR-1)和感病甜瓜(M1-15)叶片中甜瓜抗枯萎病基因(Fom-2)、几丁质酶基因(CHT)的表达变化,以探寻提高防治甜瓜枯萎病菌侵染的技术途径。结果显示:(1)外源MeJA和SA预处理接种后2品种的病情指数显著低于对照,但Ca~(2+)处理后的病情指数与对照无显著差异。(2)经外源诱导预处理接种后,MR-1和M1-15品种叶片的Fom-2和CHT基因均出现差异表达,但Ca~(2+)诱导其上调表达的效果微弱。(3)经SA、MeJA诱导预处理接种后,2品种叶片的Fom-2和CHT基因表达总体均显著高于对照;Fom-2基因的表达抗病甜瓜MR-1分别在接种后5d、7d时达到峰值,而感病甜瓜M1-15则均在接种9d时达到峰值;CHT基因的表达抗病甜瓜MR-1则均在接种后7d时达到峰值,而感病甜瓜M1-15分别在接种后7d、9d时达到峰值。(4)Ca~(2+)处理对抗、感甜瓜叶片的Fom-2和CHT基因的表达均无显著影响。(5)相关分析表明,经SA、MeJA诱导预处理接种后,甜瓜枯萎病病情指数与Fom-2和CHT基因表达量有显著的相关性;而Ca~(2+)处理效果不显著。研究表明:SA、MeJA通过诱导Fom-2、CHT基因上调表达,进而使甜瓜的抗病性提高,而Ca~(2+)处理对两基因表达和甜瓜抗病性均无显著影响。     

小麦NBS-LRR类抗病基因同源序列的分离与鉴定

根据已知植物抗病基因的保守区域设计引物,从抗锈病小麦品种西农88基因组DNA扩增出3条与植物抗病基因同源的序列,分别为WRGA1、WRGA2和WRGA14。这三条同源片段均含有典型的NBS-LRR类抗病基因所拥有的保守性结构域Kinase-2a、Kinase-3a和疏水结构域(HD)．它们与部分已知NBS-LRR类抗病基因的氨基酸序列同源性为46．0%-9．9%,三个片段间在氨基酸水平上的同源性为80．7%-56．8%。Northern杂交表明WRGA1在小麦中受水杨酸正调控,属诱导型表达。     

小麦Mlo及NBS-LRR类抗病基因同源序列的分离与鉴定

根据GenBank中公布的大麦白粉病抗性控制基因Mlo cDNA序列及一个来源于栽培一粒小麦(Triticum monococcum L.)的假定抗病基因序列分别设计引物,以携带小麦抗白粉病基因的近等基因系为材料进行RT-PCR筛选.结果获得两个表达基因的cDNA克隆.其中一个与大麦白粉病抗性控制基因Mlo的同源性达83%.另一个为非通读序列,含有两个可能的开放阅读框,分别包含抗病基因NBS保守结构域2和3以及与水稻抗稻瘟病基因Pib蛋白末端相似的13个LRR区域,推测该序列属于NBS-LRR类.白粉菌诱导前后,该片段RT-PCR扩增产物存在差异,表明该片段可能与小麦抗病性相关.利用"中国春"缺体-四体系,将该NBS-LRR类序列定位在小麦1D染色体上.     

小麦NBS类抗病基因同源cDNA序列的克隆与特征分析

根据已克隆植物抗病(R)基因NBS保守结构域设计简并引物,采用RT-PCR和cDNA末端快速扩增技术(RACE),在小麦抗叶锈病近等基因系材料TcLr19中进行抗病同源基因cDNA全长的扩增。获得了1个通读的NBS类抗病同源基因S11A11cDNA序列,该序列全长2923bp,编码878个氨基酸序列。生物信息学分析结果表明,该片段含有NB-ARC保守结构域和多个LRR结构域。聚类分析表明,S11A11编码的蛋白与小麦抗叶锈病基因Lr1编码的蛋白亲缘关系较近,而与Lr10亲缘关系较远。半定量RT-PCR分析表明,该基因在小麦叶片中为低丰度组成型表达。本研究在TcLr19小麦中成功获得了抗病基因同源序列,为最终克隆小麦抗叶锈病目的基因奠定了基础。     

小麦Mlo及NBS—LRR类抗病基因同源序列的分离与鉴定

根据GenBank中公布的大麦白粉病抗性控制基因MlocDNA序列及一个来源于栽培一粒小麦（Triticum monococcumL.)的假定抗病基因序列分别设计引物,以携带小麦抗白粉病基因的近等基因系为材料进行RT-PCR筛选。结果获得两个表达基因的cDNA克隆。其中一个与大麦白粉病抗性控制基因Mlo的同源性达83%。另一个为非通读序列,含有两个可能的开放阅读框,分别包含抗病基因NBS保守结构域2和3以及与水稻抗稻瘟病基因Pib蛋白末端相似的13个LRR区域,推测该序列属于NBS-LRR类。白粉菌诱导前后,该片段RT-PCR扩增产物存在差异。表明该片段可能与小麦抗病性相关。利用“中国春”缺体-四体系,将该NBS-LRR类序列定位在小麦1D染色体上。     

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.