种子活力与生物膜的研究现状

种子活力与生物膜的结构和功能密切相关。活力高的种子,膜结构比较完整,在吸水时,膜系统恢复的速度较快,并且修复的较完善。研究表明,超干和引发处理可使膜结构得到保持与修复,很多种类的物质参与了膜结构的保护,例如可溶性糖、蛋白质(包括酶)、两性分子、Ca2+、多胺及其他非酶促自由基清除系统等,保护物质协同作用,稳定膜脂及膜蛋白的结构,保持膜系统的完整性,使膜功能得以正常发挥,强化了种子活力。     

超干处理对胡杨种子抗逆生理生化指标的影响

以珍稀濒危植物胡杨种子为材料,采用硅胶脱水的方法制备不同含水量的种子,再经不同相对湿度的溶液对种子进行回湿处理,确定最适含水量及最适回湿方法;对最适含水量种子进行50℃高温老化处理,经回湿后测定各种酶活性、可溶性糖、可溶性蛋白及丙二醛含量,考察超干保存的效果,明确超干保存胡杨种子的可行性。结果表明:(1)当胡杨种子含水量降至3.4%时,其发芽率开始显著下降,但经回湿处理后的发芽率和发芽指数可恢复至未经超干处理样品的水平。(2)采用4种不同的方法对含水量为3.4%的种子进行回湿处理,各回湿方法处理的种子发芽率和发芽指数均显著高于未回湿处理,并以先用饱和CaCl2回湿12h后再用饱和NH4Cl回湿12h的处理效果最佳。(3)在50℃高温老化处理过程中,超干处理(含水量为3.4%)和未超干处理的胡杨种子过氧化物酶、过氧化氢酶、脱氢酶活性以及可溶性糖的含量均逐渐降低,而丙二醛的含量则逐渐升高,但超干处理种子的升降幅度明显较小。研究认为,胡杨种子超干处理的最适含水量为3.4%,超干处理种子较适宜的回湿方法是饱和CaCl2和饱和NH4Cl依次回湿处理各12h,超干处理可使胡杨种子抗氧化酶活性和可溶性糖含量于老化过程中维持在相对较高水平,膜系统伤害较轻,从而提高种子的抗老化能力,说明超干保存胡杨种子具有一定的可行性。     

种子活力与生物膜的研究现状

种子活力与生物膜的结构和功能密切相关.活力高的种子,膜结构比较完整,在吸水时,膜系统恢复的速度较快,并且修复的较完善.研究表明,超干和引发处理可使膜结构得到保持与修复,很多种类的物质参与了膜结构的保护,例如可溶性糖、蛋白质(包括酶)、两性分子、Ca2 、多胺及其他非酶促自由基清除系统等,保护物质协同作用,稳定膜脂及膜蛋白的结构,保持膜系统的完整性,使膜功能得以正常发挥,强化了种子活力.     

超干对种子活力及水分热力学特性的影响

以耐干的菜心种子和不耐干的豇豆种子为材料,研究了超干对其活力和水分吸附等温线及热力学参数（△S、△H、△G）的影响。超干使红豇豆种子活力下降,SOD、POD活性降低,膜结构受损,这些变化即发生在水分降低的干燥过程中又发生在眼干状态下的贮藏过程中,菜心种子的活力和SOD,POD的活性受超干的影响小,超干对细胞膜的轻微损伤可在萌发吸胀时得到修复,超干种子水分吸附等温线上区段1和区段2的含水量明显下降;超干种子除－△S和－△H在区段1略有所升高外,－△S、－△H在区段和2和区段3和－△G在各区段均有程度不同的下降;这些改变尤以豇豆种子较显著,说明豇豆种子的水分束缚能力低,较易失去水分吸附等温线上的强吸附水,继而引起大分子结构的改变,降低种子活力;而菜心种子则相反,能在超干状态下较好地保持酶的活性和细胞膜的结构,故适宜超干贮藏。     

宁夏压砂地不同植被类型土壤干燥化特征

该研究在观测压砂地沙枣、柠条、西瓜、枸杞及草地土壤含水量的基础上,分析比较不同植被类型的土壤含水量、水分过耗量、干燥化指数、干层厚度等土壤干燥化特征,以揭示压砂地不同植被类型的土壤干燥化效应,为宁夏中部旱区压砂地可持续发展提供理论依据。结果表明：(1)不同植被类型下0~600 cm土壤含水量、贮水量和有效贮水量均值分别为7.163%、591.978 mm和187.088 mm,土壤水分过耗量均值为274.942 mm。(2)不同植被类型的土壤剖面含水量随深度增加呈先减小后增大的趋势;除西瓜地外,其余植被类型的土壤剖面含水量明显低于当地土壤稳定湿度。(3)不同植被类型的土壤平均干燥化系数介于2.152%~85.026%,干燥化系数均值为37.674%,属严重干燥化强度,其中柠条地和沙枣地均达到强烈干燥化强度;土壤平均干层厚度达到或超过500 cm,干燥化程度由强到弱依次为柠条地>沙枣地>枸杞地>草地>西瓜地。(4)典型相关分析发现,经纬度、高程、植被类型、粉粒及砂粒含量等环境因子是影响土壤干燥化指数、干层内平均含水量等干燥化指标的重要因素。     

超干红花种子抗老化作用及其机理

红花种子含水量（ＭＣ）降至５％以下,能显著提高抗老化劣变能力;在同等老化条件下,对照种子（ＭＣ＝９．０１％）活力已大幅度下降,而超干种子的活力保持不变,超干处理对红花种子脱氢酶,过氧化氢酶（ＣＡＴ）及超氧物歧化酶（ＳＯＤ）活性均无明显影响。经同等老化处理后,超干种子脱氢酶活性明显高于对照种子。在同等老化条件下,当对照种子ＣＡＴ和ＳＯＤ活性明显下降时,超干种子仍保持较高活性。红花种子在超干老化处理后     

超干贮藏榆树种子萌发过程中ATP和可溶性糖含量的变化

经过超干(种子含水量3.73%)贮藏(普通室温下2个月)的榆树种子萌发过程中ATP与可溶性糖含量和ATP酶、淀粉酶、抗氧化酶的活性都高于对照(种子含水量9.34%,普通室温下贮臧),说明适度的超干贮藏有利于保持种子活力.     

不同贮藏条件下豆薯种子的脂质过氧化研究

豆薯(Pachyrhizuus erosus(L.)Urban)种子分别在4℃、15℃相对湿度(RH)45%及室温开放条件下贮藏,或新鲜种子进行超干处理将其含水量降到6.43%后密封贮存,以探讨种子劣变的生理机制.结果表明,豆薯种子在室温开放贮藏12个月的发芽率降至50%,24个月后发芽力完全丧失.4℃下贮藏豆薯种子最有效,贮藏后种子的电导率和紫外吸收值较低,过氧化氢酶、过氧化物酶和超氧化物歧化酶活性仍保持较高水平,种子萌发时释放出的挥发性醛也较低.适当的超干处理效果与15℃45%RH相似,但不及4℃的.     

超干种子的膜功能与糖组分的研究

采用两相法分离种子质膜,研究超干处理对种子质膜ATP酶活力及膜流动性的影响.结果表明,白菜(Brassica pekinensis(Lour.)Rupr.)、榆树(Ulmus pumila L.)种子经超干处理后,在人工老化和自然老化条件下,与在-20℃条件下贮藏的种子比较,超干贮藏种子质膜ATP酶活力和微粘度无显著变化,过于贮藏种子的效应虽有所下降,但仍比高含水量室温贮藏的对照种子为好.此结果与超干种子具较高活力水平完全一致,说明超干贮藏种子保持了质膜的生理功能,因此提高了种子的耐藏性.高效液相色谱分析结果显示超干种子中还原糖/非还原糖的比值低于高含水量种子,积累的蔗糖、水苏糖含量与超干种子的耐干力有关.玉米(Zea mays L.)种子中不含水苏糖,这可能是玉米种子较其他种子耐干力下降的原因之一.     

超干种子的膜功能与糖组分的研究

采用两相法分离种子质膜,研究超干处理对种子质膜ATP酶活力及膜流动性的影响。结果表明。白菜（Brassica pekinensis(Lour.)Rupr)。榆树（Ulmus pumilaL）种子经超干处理后,在人工老化和自然老化条件下,与在-20℃条件下贮藏的种子比较,超干贮藏种子质膜ATP酶活力和微粘度无显著变化,过干贮藏种子的效应虽有所下降,但仍比高含水量室温贮藏的对照种子为好。此结果与超干种子具较高活力水平完全一致。说明超干贮藏种子保持了质膜的生理功能。因此提高了种子的耐藏性。高效液相色谱分析结果显示超干种子中还原糖/非还原糖的比值低于高含水量种子,积累的蔗糖,水苏糖含量与超干种子的耐干力有关。玉米（Zea maysL.)种子中不含水苏糖,这可能是玉米种子较其他种子耐干力下降的原因之一。     

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.